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02Research · Supplement

L Carnitine

Measured against the 58-marker panel. Human studies found an effect on 44, no change in 6 and conflicting results on 0; 8 have no result yet.

Most studied for

General health supplementation - lipid optimization, anti-inflammatory support, metabolic health

  • Supported 44
  • No effect 6
  • Conflicting 0
  • No result yet 8
BOverall evidence grade
925Studies tracked
116Meta-analyses
594Randomized trials

01Read first

Who should be careful

From the dossier's safety review: 26 cautions and 25 interactions, 11 rated serious. They summarize research and labels; they are not advice for you.

Cautions26

  • SeriousPrimary systemic carnitine deficiency (OCTN2/SLC22A5 loss-of-function)Grade A

    Absence of functional OCTN2 transporter causes urinary wasting.

  • SeriousDL-carnitine (racemic mixture) useGrade B

    D-carnitine (the unnatural stereoisomer) competitively inhibits L-carnitine at OCTN2 transporter and can precipitate symptomatic carnitine deficiency. Racemic supplements are dangerous.

  • SeriousCPT2 deficiency (severe neonatal or hepatocardiomuscular form)Grade C

    Severe CPT2 deficiency impairs acylcarnitine translocation across inner mitochondrial membrane. Longo 2006 notes management is primarily dietary fat restriction.

  • SeriousCarnitine-acylcarnitine translocase (CACT) deficiencyGrade C

    CACT deficiency (SLC25A20) blocks inner mitochondrial membrane carnitine shuttle. L-carnitine supplementation may increase long-chain acylcarnitine accumulation with cardiac arrhythmia risk.

Show 22 more

  • SeriousCPT1A deficiency (hepatic form)Grade C

    CPT1A deficiency impairs long-chain fatty acid entry into mitochondrial matrix. Supplemental carnitine may not be harmful but will not address the enzymatic block.

  • SeriousHypersensitivity / allergy to carnitine or excipientsGrade C

    Rare but documented; anaphylactic reactions to L-carnitine preparations reported in case literature

  • SeriousHypersensitivity to L-carnitine or any formulation excipient

    Rare type I or delayed hypersensitivity reactions reported with L-carnitine administration

  • SeriousConcurrent pivalate-containing antibiotic therapy

    Pivalic acid from pivampicillin/pivmecillinam prodrug hydrolysis obligately consumes carnitine, forming non-recyclable pivaloylcarnitine. Net carnitine depletion occurs.

  • ModerateActive hypothyroidism requiring full levothyroxine replacementGrade B

    L-carnitine inhibits thyroid hormone entry into cell nuclei (peripheral antagonism). May functionally reduce efficacy of thyroid replacement therapy, worsening hypothyroid state.

  • ModerateEnd-stage renal disease (ESRD) without dialysisGrade B

    Carnitine and acylcarnitines accumulate in renal failure due to impaired excretion; supplementation may worsen acylcarnitine imbalance.

  • ModerateEstablished cardiovascular disease with elevated TMAO concernGrade B

    Gut microbial metabolism of L-carnitine generates TMA → hepatic TMAO. Elevated circulating TMAO associated with atherosclerosis and MACE risk in observational studies.

  • ModerateSeizure disorder (history of seizures without adequate control)Grade C

    ALCAR has been reported to lower seizure threshold in some case reports; mechanism unclear.

  • ModerateTrimethylaminuria (fish odor syndrome) / FMO3 deficiencyGrade C

    L-carnitine is converted to TMA by gut bacteria; TMA is normally oxidized by hepatic FMO3 to odorless TMAO.

  • ModeratePivalate antibiotic-induced secondary carnitine deficiency (myopathic presentation)Grade C

    Caveat: Rose 1992 showed that recovery is slow even with oral supplementation — gut carnitine absorption may be partially impaired during pivalate exposure. IV carnitine may be required for severe cases.

  • ModeratePregnancy — high-dose supplementationGrade D

    Placental OCTN2 actively transports carnitine to fetus; maternal status affects fetal supply.

  • ModerateSevere or end-stage renal impairment (eGFR <15 mL/min/1.73m²) without dialysis

    Severely impaired renal excretion leads to carnitine and acylcarnitine accumulation; disrupts acylcarnitine:free carnitine homeostasis.

  • ModerateSevere hepatic impairment (Child-Pugh C)

    Liver is primary site of FMO3-mediated TMAO production from gut-derived TMA; hepatic impairment alters FMO3 expression and carnitine biosynthesis via BBOX1.

  • ModerateSeizure disorder with active or recent seizures

    L-carnitine may lower seizure threshold in some individuals; conversely, carnitine supplementation is often indicated in valproate-treated epilepsy due to VPA-induced carnitine depletion.

  • ModeratePre-operative period (within 7 days of surgery) — IV formulation

    risk compounded in anesthetized patients or those on antihypertensives. IV carnitine may also alter fatty acid metabolism that is relevant to cardiac anesthesia management.

  • ModeratePregnancy (all trimesters) — high-dose supplementation beyond established PCD therapeutic doses

    Carnitine crosses the placenta; fetal carnitine concentrations exceed maternal plasma levels.

  • ModerateLactation — high-dose supplementation

    L-carnitine is present in breast milk; carnitine content increases with supplementation.

  • ModerateKnown TMAO cardiovascular risk — high-dose oral supplementation in omnivorous patients with established cardiovascular disease

    Oral L-carnitine (≥2 g/day) in omnivores with intact gut microbiome generates substantial TMAO; TMAO inhibits macrophage reverse cholesterol transport (~30%), promotes atherosclerotic plaque formation (ApoE-/- mouse: plaque doubled with chronic carnitine supplementation,…

  • ModerateBiliary obstruction or severe cholestasis

    Oral L-carnitine absorption is partially bile-dependent. Biliary obstruction reduces intestinal bile acid availability, impairing fat-soluble compound absorption and GI motility.

  • ModerateInflammatory bowel disease (Crohn's disease, ulcerative colitis) — active flare

    PMID:37927485 PCD cohort data). GI motility effects also reduce carnitine transit time, potentially reducing absorption.

  • ModeratePediatric use without confirmed carnitine deficiency or established indication

    Endogenous carnitine synthesis and renal carnitine handling mature postnatally; Supplementation without deficiency confirmation may disrupt developing fatty acid oxidation regulatory feedback.

  • ModerateHypothyroidism — inadequately controlled or requiring full T4 replacement

    L-carnitine antagonizes thyroid hormone action at the nuclear receptor level (peripheral antagonism); reduces T4→T3 peripheral conversion.

Interactions25

  • SeriousPivalic acid-containing antibiotics (pivampicillin, pivmecillinam, cefditoren pivoxil, talampicillin)Grade B

    Pivalic acid (2,2-dimethylpropionic acid) released from prodrug hydrolysis is obligately conjugated with carnitine to form pivaloylcarnitine; pivaloylcarnitine is excreted renally and does not release free carnitine.

  • SeriousValproic acid (valproate)Grade C

    Valproate forms valproylcarnitine esters via mitochondrial β-oxidation pathway; net urinary carnitine wasting.

  • SeriousPivampicillin / pivmecillinam / cefditoren pivoxilGrade C

    Pivalic acid released from prodrug hydrolysis conjugates with carnitine to form pivaloylcarnitine, which is renally excreted without reclamation. Net urinary carnitine loss can exceed 50% of daily turnover with prolonged use.

  • ModerateThyroid hormones (levothyroxine, liothyronine)Grade B

    L-carnitine competitively inhibits thyroid hormone entry into cell nuclei by acting as a peripheral thyroid hormone antagonist; reduces conversion of T4 to T3 in peripheral tissues.

Show 21 more

  • ModerateThyroid hormone (levothyroxine)Grade B

    L-carnitine acts as a functional thyroid hormone antagonist at the nuclear receptor level; inhibits T3 and T4 entry into cell nuclei in peripheral tissues

  • ModerateZidovudine (AZT) and other NRTIsGrade B

    NRTIs inhibit mitochondrial DNA polymerase gamma (POLG), causing mitochondrial dysfunction and secondary carnitine deficiency. ALCAR levels elevated in HIV/ATN patients relative to healthy controls (Herzmann 2008) — paradoxical elevation may reflect impaired peripheral ALCAR…

  • ModerateDidanosine (ddI) / stavudine (d4T)Grade B

    Older NRTIs with highest mitochondrial toxicity burden; disproportionately associated with NRTI-toxic neuropathy (ATN) for which ALCAR has been specifically studied.

  • ModerateD-carnitine (dietary supplement contaminant)Grade B

    D-carnitine competitively inhibits L-carnitine cellular uptake via OCTN2 and can induce functional carnitine deficiency even in presence of adequate L-carnitine. Relevant if supplement purity is inadequate.

  • ModerateValproic acid (VPA)Grade C

    VPA inhibits carnitine transport and renal reabsorption; impairs mitochondrial beta-oxidation.

  • ModerateCyclosporine (ciclosporin)Grade C

    Cyclosporine inhibits OCTN2 (SLC22A5)-mediated renal tubular reabsorption of carnitine; increases urinary carnitine excretion.

  • ModerateNucleoside reverse transcriptase inhibitors (NRTIs: zidovudine, stavudine, didanosine)Grade C

    NRTIs cause mitochondrial toxicity via γ-DNA polymerase inhibition; secondary carnitine deficiency occurs due to impaired mitochondrial fatty acid oxidation and increased acylcarnitine production with reduced free carnitine.

  • ModerateMeldonium (Mildronate)Grade C

    Meldonium competitively inhibits gamma-butyrobetaine hydroxylase (BBOX1), the rate-limiting enzyme in endogenous carnitine biosynthesis, and inhibits OCTN2 (SLC22A5)-mediated renal tubular reabsorption of carnitine, resulting in net carnitine depletion. Co-administration of…

  • ModerateSodium BenzoateGrade C

    Sodium benzoate is conjugated with glycine (via benzoyl-CoA intermediate) to form hippurate for renal excretion in urea cycle disorder management. Urinary acylcarnitine profile shifts: benzoylcarnitine appears.

  • ModerateWarfarinGrade C

    L-carnitine may enhance anticoagulant effect via unknown mechanism; possibly altered hepatic vitamin K-dependent clotting factor synthesis or displacement from plasma proteins

  • ModerateCisplatinGrade C

    Cisplatin causes nephrotoxicity and neuropathy partly via mitochondrial injury; carnitine depletion has been documented post-cisplatin.

  • ModerateCarbamazepineGrade C

    Carbamazepine, like valproate, has been associated with secondary carnitine depletion, particularly in pediatric polypharmacy. Mechanism involves increased acylcarnitine formation and excretion.

  • ModeratePhenobarbital / primidoneGrade C

    Associated with secondary carnitine depletion in pediatric studies, particularly in polypharmacy. Mechanism includes increased acylcarnitine formation and impaired biosynthesis

  • ModerateEnalapril / ACE inhibitorsGrade C

    No established pharmacokinetic interaction; however, carnitine supplementation and ACE inhibitors may have additive cardioprotective effects in heart failure/post-MI settings.

  • ModerateMetforminGrade D

    Metformin is an organic cation that uses OCTN1 (SLC22A4) and OCT transporters for intestinal absorption and renal excretion; competitive inhibition of carnitine intestinal uptake via OCTN1/OCTN2 reported in vitro.

  • ModerateWarfarin and anticoagulantsGrade D

    L-carnitine has been reported to potentiate warfarin anticoagulation in case reports; proposed mechanism involves carnitine-mediated effects on hepatic coagulation factor synthesis or CYP2C9 expression modulation.

  • ModerateAcenocoumarol / phenprocoumonGrade D

    Same class as warfarin; pharmacovigilance signals for enhanced anticoagulation with carnitine apply by extension to all VKAs

  • MinorStatins (atorvastatin, simvastatin, rosuvastatin)Grade C

    Bidirectional interaction: (1) Statins inhibit CoA-related mitochondrial pathways and may cause secondary carnitine depletion; corpus: 6 atorvastatin interaction signals.

  • MinorIsotretinoin (13-cis-retinoic acid)Grade D

    Isotretinoin alters fatty acid metabolism and causes mitochondrial dysfunction in skin and liver; acylcarnitine accumulation observed with retinoid treatment.

  • MinorAminoglycosides (gentamicin, tobramycin, amikacin)Grade D

    Aminoglycosides cause nephrotoxicity via proximal tubular cell injury; impaired OCTN2 function in damaged renal proximal tubular cells reduces carnitine reabsorption.

  • MinorTrimethoprim-sulfamethoxazole (TMP-SMX)Grade D

    additive renal tubular competition possible given OCTN2 renal transport role. Clinical significance unclear.

02What it moves

50 markers studied

One row per marker on the panel that human studies measured. Open a row for the direction, who was studied, and the papers.

Read with this in mind

Short-term signal (<=24w) is statistically robust but not sustained at 52w; clinical meaningfulness disputed; ALCAR-specific - does not apply to other carnitine forms

Mortality benefit is biologically plausible and may be real in acute ischemic/deficiency contexts; oral supplementation benefit for all-cause mortality in stable, medication-managed CAD is unconfirmed

Performance benefit in healthy athletes without insulin-mediated loading protocols is not well-supported; benefit concentrated in clinical populations with carnitine deficiency

Blood sugar4 of 4 studied

HbA1cLowersGrade A

L-carnitine lowers HbA1c.

Meta-analysis or review · Modest effect · 20 studies linked

Studied in: T2DM, Metabolic syndrome

Effect on HbA1c smaller and less consistent than fasting glucose reduction; WMD approximately -0.2 to -0.4% in meta-analyses; longer-duration trials needed

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Fasting glucoseLowersGrade A

L-carnitine lowers fasting glucose.

Meta-analysis or review · Small effect · 2 studies linked

Studied in: T2DM, Metabolic syndrome, Prediabetes, PCOS

Modest absolute reduction from mildly elevated baseline; before-after

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Fasting insulinLowersGrade B

L-carnitine lowers fasting insulin.

Moderate effect · 1 study linked

Studied in: PCOS, Female, Hyperinsulinemic

Large proportional reduction from high baseline; PCOS hyperinsulinemia context; before-after

  • Salehpour S, Nazari L, Hoseini S, Hosseini MS, Azizi E, Ghasemnejad-Berenji H (2019)
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HOMA-IRLowersGrade A

L-carnitine lowers HOMA-IR.

Meta-analysis or review · Moderate effect · 29 studies linked

Studied in: T2DM, PCOS, Metabolic syndrome, NAFLD

Mingorance 2012 (PLC, DIO mice): HOMA-IR reduced 52% (31.28→14.83, p<0.001). Adds grade C animal corroboration for insulin sensitization mechanism (propionyl-L-carnitine). Effect mediated via hepatic mitochondrial function restoration and visceral fat reduction rather than direct ceramide/GLUT4 pathway. No change in...

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Lipids6 of 6 studied

LDL-CLowersGrade A

L-carnitine lowers LDL-C.

Meta-analysis or review · Modest effect · 60 studies linked

Studied in: General adult, T2DM, CAD, PCOS

91 studies; consolidated from ldl_c, ldl_cholesterol, LDL_cholesterol entries. Effect smaller and less consistent than TG. PCOS-specific data (Salehpour 2019, before-after) contributes C-level evidence within overall B-grade biomarker.

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HDL-CRaisesGrade A

L-carnitine raises HDL-C.

Meta-analysis or review · Modest effect · 36 studies linked

Studied in: General adult, T2DM, CKD, Dyslipidemia

101 studies; consolidated from hdl_c, hdl_cholesterol, HDL_cholesterol entries. Small effect size. Wang 2020 confirms direction in animal model.

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TriglyceridesLowersGrade A

L-carnitine lowers triglycerides.

Meta-analysis or review · Moderate effect · 69 studies linked

Studied in: General adult, T2DM, CKD, Dyslipidemia

333 studies in corpus — strongest evidence domain. Consolidated with triglycerides entry. Multiple meta-analyses confirm direction and magnitude. Animal contradiction: Talari 2019 (PLC, DIO mice) showed no TG reduction (ns) despite TC improvement — PLC vs LC form difference or short duration may explain. Preserved a...

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Total cholesterolLowersGrade A

L-carnitine lowers total cholesterol.

Meta-analysis or review · Modest effect · 1 study linked

Studied in: General adult, T2DM, CAD, Dyslipidemia

166 studies in corpus; Wang 2020 animal corroborates direction; TC effect consistently smaller than TG reduction

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ApoBLowersGrade A

L-carnitine lowers ApoB.

Meta-analysis or review · Modest effect · 10 studies linked

Studied in: General adult, Dyslipidemia

4 studies in corpus; limited but direction consistent with reduced VLDL/LDL particle number. Grade C due to sparse human data.

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Lp(a)LowersGrade A

L-carnitine lowers Lp(a).

Meta-analysis or review · 8 studies linked

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Inflammation5 of 5 studied

hs-CRPLowersGrade A

L-carnitine lowers hs-CRP.

Meta-analysis or review · Moderate effect · 40 studies linked

Studied in: General adult, T2DM, CKD, CAD

88 studies in corpus; anti-inflammatory effect consistent across chronic disease populations; Wang 2020 confirms ↓CRP in animal model

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IL-6LowersGrade A

L-carnitine lowers IL-6.

Meta-analysis or review · Modest effect · 21 studies linked

Studied in: General adult, T2DM, CKD

Corpus coverage moderate; effect direction consistent with NF-κB suppression mechanism but magnitude varies substantially by population and dose

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TNF-αLowersGrade A

L-carnitine lowers TNF-α.

Meta-analysis or review · Moderate effect · 15 studies linked

Studied in: General adult, T2DM, CKD, Animal model

131 studies in corpus — largest inflammatory marker dataset. Consolidated with tnf_alpha tier_2 entry. Wang 2020 confirms direction in animal model. Human RCT effect sizes heterogeneous.

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ESRLowersGrade B

L-carnitine lowers ESR.

Human trials · 2 studies linked

4 studies in corpus; ESR is rarely reported as a carnitine trial endpoint. Nonspecific marker.

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FibrinogenLowersGrade B

L-carnitine lowers fibrinogen.

Human trials · 2 studies linked

6 studies in corpus; insufficient dedicated data. Fibrinogen is an acute phase reactant and coagulation factor; L-carnitine's anti-inflammatory mechanism could theoretically reduce it but evidence is absent.

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Liver5 of 6 studied

ALTLowersGrade A

L-carnitine lowers ALT.

Meta-analysis or review · Modest effect · 41 studies linked

Studied in: NAFLD, T2DM, General adult

92 studies in corpus; hepatoprotective effect most pronounced in NAFLD and T2DM populations; parallels CPT-I activation reducing hepatic lipid accumulation

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ASTLowersGrade A

L-carnitine lowers AST.

Meta-analysis or review · Modest effect · 104 studies linked

Studied in: NAFLD, T2DM, General adult

88 studies in corpus; parallel reduction with ALT; hepatic effect consistent; AST/ALT ratio changes not consistently reported

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ALPLowersGrade A

L-carnitine lowers ALP.

Meta-analysis or review · 18 studies linked

Studied in: General adult

36 studies in corpus mention ALP but dedicated effect extraction not completed. ALP elevation is more indicative of cholestatic than hepatocellular pathology; L-carnitine's hepatoprotective mechanism (CPT-I, steatosis reduction) would primarily affect hepatocellular markers.

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BilirubinLowersGrade A

L-carnitine lowers bilirubin.

Meta-analysis or review · 6 studies linked

Studied in: General adult

28 studies in corpus; bilirubin not a primary endpoint in L-carnitine trials. No mechanistic basis for direct bilirubin modulation.

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AlbuminRaisesGrade A

L-carnitine raises albumin.

Meta-analysis or review · Modest effect · 17 studies linked

Studied in: CKD, Dialysis, Cancer cachexia

89 studies in corpus; albumin improvement reported primarily in malnutrition-associated contexts (dialysis malnutrition, cancer cachexia). Mechanism: improved hepatic protein synthesis via mitochondrial energy support. Not expected to change albumin in well-nourished populations.

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Kidney4 of 4 studied

CreatinineLowersGrade A

L-carnitine lowers creatinine.

Meta-analysis or review · Modest effect · 9 studies linked

Studied in: CKD, Dialysis, ESRD

105 studies in corpus; evidence concentrated in CKD/dialysis populations; reflects improved metabolic efficiency and reduced muscle catabolism rather than direct GFR improvement

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eGFRArtifactGrade B

L-carnitine shifts the eGFR reading, likely a measurement artifact rather than a real change.

Human trials · 3 studies linked

Likely a measurement artifact rather than a real change; see the note.

Studied in: CKD

7 studies in corpus; eGFR is rarely a primary endpoint in carnitine trials. Creatinine reduction in CKD may reflect reduced catabolism rather than true GFR improvement; eGFR derived from creatinine would thus be artifactually elevated.

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BUNLowersGrade A

L-carnitine lowers BUN.

Meta-analysis or review · Modest effect · 4 studies linked

Studied in: CKD, Dialysis

Often co-reported with creatinine in CKD/dialysis trials; direction consistent with reduced catabolism; effect size similar to creatinine

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Cystatin CLowersGrade B

L-carnitine lowers cystatin C.

Human trials · 2 studies linked

6 studies in corpus; cystatin C is a GFR-independent renal marker. If carnitine truly improves renal function (vs. merely reducing creatinine generation), cystatin C would provide confirmatory evidence. Data gap.

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Blood and iron5 of 7 studied

HemoglobinRaisesGrade A

L-carnitine raises hemoglobin.

Meta-analysis or review · Modest effect · 20 studies linked

Studied in: CKD, Dialysis, ESRD, Anemia

84 studies in corpus; benefit concentrated in dialysis/ESRD populations; reduces EPO requirements; minimal effect in populations without baseline carnitine depletion

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HematocritRaisesGrade A

L-carnitine raises hematocrit.

Meta-analysis or review · Modest effect · 3 studies linked

Studied in: CKD, Dialysis

24 studies; parallels hemoglobin response in dialysis populations. Reflects improved RBC mass.

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Red cellsRaisesGrade C

L-carnitine raises red cells.

Human trials · Modest effect · 0 studies linked

This result is graded, but no study is linked to it yet. Treat it as unconfirmed.

Studied in: CKD, Dialysis, Anemia

23 studies in corpus; RBC count improvement parallels hemoglobin increase in dialysis populations. Effect secondary to improved erythropoiesis and erythrocyte membrane stability.

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PlateletsRaisesGrade B

L-carnitine raises platelets.

Human trials · 5 studies linked

42 studies mention platelets but dedicated effect data not extracted. No known direct mechanism.

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FerritinNo changeGrade B

Studies of L-carnitine found no change in ferritin.

Human trials · 3 studies linked

Studied in: CKD, Dialysis

16 studies; ferritin is co-reported with hemoglobin in dialysis anemia trials. L-carnitine's EPO-sparing effect may indirectly improve iron utilization but direct ferritin modulation not established.

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Hormones5 of 5 studied

TestosteroneNo changeGrade A

Studies of L-carnitine found no change in testosterone.

Meta-analysis or review · 16 studies linked

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EstradiolRaisesGrade B

L-carnitine raises estradiol.

Human trials · 3 studies linked

Studied in: PCOS, Female

15 studies; some PCOS trials report estradiol but direction not consistently extractable.

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SHBGNo changeGrade A

Studies of L-carnitine found no change in SHBG.

Meta-analysis or review · 2 studies linked

4 studies in corpus; insufficient dedicated effect data.

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CortisolLowersGrade B

L-carnitine lowers cortisol.

Human trials · 3 studies linked

13 studies; exercise studies sometimes report cortisol but dedicated effect data not available.

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DHEA-SLowersGrade B

L-carnitine lowers DHEA-S.

Human trials · 3 studies linked

9 studies; insufficient dedicated effect data.

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Thyroid1 of 4 studied

TSHRaisesGrade B

L-carnitine raises TSH.

Human trials · Modest effect · 2 studies linked

Studied in: Hyperthyroid, Euthyroid on replacement

8 studies in corpus. L-carnitine is a peripheral thyroid hormone antagonist (mech_011); TSH may rise compensatorily when peripheral thyroid action is blunted. Most data from hyperthyroid treatment context (Benvenga et al.). Euthyroid individuals unlikely to see clinically significant TSH change at standard doses.

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Heart2 of 2 studied

NT-proBNPLowersGrade A

L-carnitine lowers NT-proBNP.

Meta-analysis or review · Modest effect · 8 studies linked

Studied in: Heart failure, CKD, Dialysis

11 studies; NT-proBNP reduction reported in heart failure and dialysis contexts. Reflects improved cardiac function (LVEF improvement) rather than direct biomarker modulation.

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TroponinLowersGrade B

L-carnitine lowers troponin.

Human trials · Modest effect · 6 studies linked

Studied in: Post MI, Cardiac surgery

12 studies; troponin reduction reported in post-MI and cardiac surgery contexts, consistent with cardioprotective mechanism. Reflects reduced myocardial injury.

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Oxidative stress4 of 4 studied

MDALowersGrade A

L-carnitine lowers MDA.

Meta-analysis or review · Moderate effect · 29 studies linked

Studied in: Animal model, CKD, General adult

Wang 2020: significant ↓MDA in ApoE-/- mice; oxidative stress reduction corroborated in human CKD/dialysis context but MDA-specific human RCT data sparse

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F2-isoprostanesLowersGrade B

L-carnitine lowers F2-isoprostanes.

Human trials · Modest effect · 2 studies linked

Studied in: General adult

9 studies; F2-isoprostanes reflect arachidonic acid oxidation. Reduction consistent with membrane lipid peroxidation protection.

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8-OHdGLowersGrade C

L-carnitine lowers 8-OHdG.

Human trials · Modest effect · 1 study linked

Studied in: CKD, General adult

8 studies; 8-OHdG is a DNA oxidation marker. Reduction consistent with antioxidant mechanism (mech_004). Limited human RCT data as primary endpoint.

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GlutathioneRaisesGrade A

L-carnitine raises glutathione.

Meta-analysis or review · Modest effect · 11 studies linked

Studied in: CKD, General adult

197 studies in corpus; GSH/GSSG ratio improvement (increased reduced glutathione) is consistent with antioxidant enzyme upregulation (mech_004). Large corpus but many studies report GSH tangentially.

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B vitamins3 of 4 studied

HomocysteineRaisesGrade B

L-carnitine raises homocysteine.

Meta-analysis or review · 2 studies linked

23 studies in corpus; direction not consistently extractable. Theoretical basis for interaction: carnitine biosynthesis requires S-adenosylmethionine, competing with homocysteine remethylation. See OQ-019.

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Vitamin B12No changeGrade B

Studies of L-carnitine found no change in vitamin B12.

Meta-analysis or review · 1 study linked

13 studies; no direct carnitine-B12 interaction mechanism.

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MMALowersGrade A

L-carnitine lowers MMA.

Meta-analysis or review · 15 studies linked

10 studies; MMA is a B12 functional marker. No direct carnitine interaction.

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Minerals4 of 5 studied

SodiumNo changeGrade D

Studies of L-carnitine found no change in sodium.

0 studies linked

This result is graded, but no study is linked to it yet. Treat it as unconfirmed.

138 studies mention sodium; typically reported as safety parameter. L-carnitine does not meaningfully affect serum sodium at therapeutic doses. OCTN2 is a sodium-dependent cotransporter but operates at renal/intestinal level, not affecting systemic sodium homeostasis.

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PotassiumNo changeGrade D

Studies of L-carnitine found no change in potassium.

0 studies linked

This result is graded, but no study is linked to it yet. Treat it as unconfirmed.

13 studies; safety parameter in CKD/dialysis trials. No direct mechanism for potassium modulation.

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CalciumImprovesGrade B

L-carnitine improves calcium.

Human trials · 3 studies linked

65 studies; commonly co-reported in CKD/dialysis trials as safety parameter. No direct carnitine-calcium interaction.

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PhosphateLowersGrade B

L-carnitine lowers phosphate.

Meta-analysis or review · 4 studies linked

134 studies; co-reported in CKD/dialysis. No direct mechanism for phosphate modulation by L-carnitine.

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Body2 of 2 studied

Blood pressureLowersGrade A

L-carnitine lowers blood pressure.

Meta-analysis or review · 15 studies linked

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Weight and BMILowersGrade A

L-carnitine lowers weight and BMI.

Meta-analysis or review · 32 studies linked

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Also measured20 outcomes

Outcomes these studies measured that are not on the shared panel, so they are not on the map.

Waist CircumferenceLowersGrade A

L-carnitine lowers waist Circumference.

Meta-analysis or review · 16 studies linked

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CGI-I (Clinical Global Impression of Improvement)ImprovesGrade B

L-carnitine improves CGI-I (Clinical Global Impression of Improvement).

Meta-analysis or review · Moderate effect · 1 study linked

Studied in: Elderly, MCI, Alzheimer, Dementia

Hudson 2003: OR 1.90 (95% CI 1.31–2.76) at 12w; OR 2.33 (95% CI 1.31–4.14) at 24w; no significant benefit at 52w; ALCAR-specific; trial pool from 1980s–1990s (older diagnostic criteria)

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Ecog performance statusChangesGrade B

L-carnitine changes ecog performance status.

Moderate effect · 1 study linked

Studied in: Cancer cachexia, Advanced cancer

Mantovani 2010 Arm 3: L-carnitine 4g/day × 4 months produced statistically significant improvement in ECOG PS in cancer cachexia patients. This is a functional performance endpoint, not a serum biomarker, but relevant to clinical utility of LC in oncology.

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Intradialytic hypotensionLowersGrade B

L-carnitine lowers intradialytic hypotension.

Large effect · 1 study linked

Studied in: Hemodialysis, CKD esrd, Japanese, Adult

Clinically significant reduction in intradialytic hypotension episodes. Mechanism likely involves improved cardiac contractility (LVEF) and peripheral vascular tone via carnitine-dependent myocardial and smooth muscle energy metabolism. Single small RCT — requires replication.

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LVEF hdRaisesGrade B

L-carnitine raises LVEF hd.

Modest effect · 1 study linked

Studied in: Hemodialysis, CKD esrd, Japanese, Adult

Single RCT evidence in HD patients. Effect may reflect correction of carnitine deficiency driving impaired myocardial fatty acid oxidation in dialysis-dependent patients. Generalizability beyond ESRD/HD population is uncertain. Other echocardiographic parameters did not reach significance in this study.

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MMSE (Mini-Mental State Examination)RaisesGrade B

L-carnitine raises MMSE (Mini-Mental State Examination).

Meta-analysis or review · Modest effect · 1 study linked

Studied in: Elderly, MCI, Alzheimer, Dementia

Hudson 2003 Cochrane SR (16 RCTs): MMSE WMD +0.69 at 24 weeks; benefit not maintained at 52 weeks; ALCAR-specific — does not generalize to L-carnitine tartrate or fumarate forms

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Plasma free carnitine hdRaisesGrade B

L-carnitine raises plasma free carnitine hd.

Large effect · 1 study linked

Studied in: Hemodialysis, CKD esrd, Japanese, Adult

HD patients have chronic carnitine deficiency due to dialytic losses and reduced renal biosynthesis. Oral 900 mg/day for 3 months produces dramatic repletion. Acyl carnitine fraction similarly increased (15.8→94.8 μmol/L). Effect is population-specific — general population baseline carnitine levels are normal and re...

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Sperm morphologyRaisesGrade B

L-carnitine raises sperm morphology.

Moderate effect · 1 study linked

Studied in: Male, Infertile, Smokers

Paradoxical subgroup finding — needs replication with placebo-controlled design; absolute morphology values not available from summary

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Sperm Motility (Progressive)RaisesGrade B

L-carnitine raises sperm Motility (Progressive).

Human trials · Moderate effect · 1 study linked

Studied in: Male, Infertility, Oligospermia, Asthenospermia

Before-after; subgroup differential is the key clinical finding from this paper

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Fatigue (VAS / Patient-Reported Scores)LowersGrade B

L-carnitine lowers fatigue (VAS / Patient-Reported Scores).

Human trials · Moderate effect · 0 studies linked

This result is graded, but no study is linked to it yet. Treat it as unconfirmed.

Studied in: CKD, Dialysis, Cancer, General adult

Anti-fatigue effect consistent in CKD/dialysis and cancer-related fatigue populations; mechanism via improved mitochondrial ATP production; effect in healthy populations less established

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LVEF (Left Ventricular Ejection Fraction)RaisesGrade B

L-carnitine raises LVEF (Left Ventricular Ejection Fraction).

Human trials · Modest effect · 0 studies linked

This result is graded, but no study is linked to it yet. Treat it as unconfirmed.

Studied in: CAD, Heart failure, Post MI

Mingorance 2012 (PLC, DIO mice): Cardiac index significantly improved (p<0.05); ejection fraction unchanged between groups. Cardiac output improvement driven by PLC's effect on body weight normalization and NO enhancement, not direct inotropy. Supports carnitine-mediated cardiac metabolic efficiency in obese/insulin...

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Sperm Count / ConcentrationRaisesGrade B

L-carnitine raises sperm Count / Concentration.

Human trials · Modest effect · 0 studies linked

This result is graded, but no study is linked to it yet. Treat it as unconfirmed.

Studied in: Male, Infertility, Oligospermia

Improvement in sperm concentration and morphology; less consistent than motility effect; treatment duration ≥3 months appears necessary for significant change

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VO2 maxRaisesGrade B

L-carnitine raises VO2 max.

Human trials · Modest effect · 0 studies linked

This result is graded, but no study is linked to it yet. Treat it as unconfirmed.

Studied in: CAD, Heart failure, Cardiac rehabilitation, General adult

Improvement most robust in CAD/cardiac rehab populations; effect in healthy trained athletes less consistent and contested; benefit may require clinical-level carnitine deficiency

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IL-1βLowersGrade C

L-carnitine lowers IL-1β.

Lab or animal studies · Modest effect · 1 study linked

Studied in: Animal model, Atherosclerosis

Wang 2020: significant ↓IL-1β in ApoE-/- atherosclerotic model; limited direct human evidence for IL-1β specifically; grade C pending human RCT replication

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Plasma AmmoniaLowersGrade C

L-carnitine lowers plasma Ammonia.

Human trials · Large effect · 1 study linked

Studied in: Hepatic encephalopathy, Cirrhosis, ESRD, Vpa treated

ALCAR reduces ammonia in hepatic encephalopathy; mechanism via enhanced urea cycle substrate availability; evidence strongest in overt hepatic encephalopathy, less data in minimal HE

  • Vázquez M et al. (2014)
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SOD (Superoxide Dismutase Activity)RaisesGrade C

L-carnitine raises SOD (Superoxide Dismutase Activity).

Lab or animal studies · Moderate effect · 1 study linked

Studied in: Animal model, CKD

Wang 2020: statistically significant ↑SOD in ApoE-/- model; human supplementation trials measuring SOD activity directly are limited; grade upgrade pending RCT replication

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VLDL CholesterolLowersGrade C

L-carnitine lowers VLDL Cholesterol.

Lab or animal studies · Modest effect · 1 study linked

Studied in: Animal model, Atherosclerosis

Wang 2020: significant ↓VLDL in ApoE-/- mice; limited direct human evidence for VLDL specifically; mechanistically consistent with hepatic CPT-I activation

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Fatigue cancerMixed resultsGrade B

Studies of L-carnitine and fatigue cancer disagree.

1 study linked

Studied in: Cancer cachexia, Advanced cancer

Mantovani 2010 (n=332 Phase III RCT) shows L-carnitine 4g/day monotherapy does NOT significantly improve cancer-related fatigue as a standalone intervention. Fatigue benefit appears only in combination protocols. Prior C-grade mechanistic evidence for fatigue remains; this B-grade RCT adds important null finding for...

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Growth / Weight Gain (Preterm Infant)Mixed resultsGrade B

Studies of L-carnitine and growth / Weight Gain (Preterm Infant) disagree.

Human trials · 1 study linked

Studied in: Preterm infant, Neonatal, VLBW

Shortland 1998 (n=86, 25 mg/kg/day IV): no significant difference in growth parameters or hypoglycemia despite successful plasma carnitine repletion; biochemical effect without clinical benefit

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Apnea Episodes (Preterm Infant)Mixed resultsGrade D

Studies of L-carnitine and apnea Episodes (Preterm Infant) disagree.

Human trials · 1 study linked

Studied in: Preterm infant, Neonatal

Kumar 2004 Cochrane SR: no eligible RCTs identified for carnitine supplementation in preterm apnea; evidence gap — absence of trials, not demonstrated null effect

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How it might work4

Proposed mechanisms. Most rest on lab and animal work, so read them as explanations, not proof of an effect.

  • Long-chain fatty acid mitochondrial transport via carnitine palmitoyltransferase I/II (CPT-I/CPT-II) - L-carnitine forms acylcarnitine esters enabling translocation of acyl groups across the inner mitochondrial membrane for beta-oxidation
  • Acyl-CoA / free CoA buffering - carnitine accepts acyl groups from acyl-CoA, regenerating free CoA-SH and preventing toxic acyl-CoA accumulation in mitochondrial matrix; modulates acetyl-CoA:CoA ratio and downstream metabolic flux
  • NF-kB pathway suppression - ALCAR and LC reduce nuclear translocation of NF-kB p65, attenuating transcription of pro-inflammatory cytokines (TNF-alpha, IL-1beta, IL-6); observed in endothelial and macrophage cell models
  • ROS scavenging and antioxidant enzyme upregulation - LC/ALCAR increase superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity; reduce lipid peroxidation (MDA) via mitochondrial membrane stabilization and free radical quenching

03No result yet

8 markers

8 markers on the panel have no result for L Carnitine yet. A gap is not a negative result.

Not yet reviewed8

No study in this dossier reported these, and they haven't been searched for one by one yet.

Liver
GGT
Blood and iron
MCVWhite cells
Thyroid
Free T3Free T4Reverse T3
B vitamins
Folate
Minerals
Magnesium

Open questions4

  • Does L-carnitine supplementation reliably increase skeletal muscle carnitine content in humans without concurrent insulin/carbohydrate co-ingestion?
  • What is the efficacy and safety of L-carnitine supplementation in pediatric populations aged 1-17 years without inborn errors of metabolism?
  • Does chronic (>2 year) high-dose oral L-carnitine supplementation increase cardiovascular events via sustained TMAO elevation in omnivorous populations?
  • What is the long-term safety profile of L-carnitine in pregnant women at pharmacologic doses (>1g/day)?
See these gaps on the map →Commission research on a gap →

04The studies and genetics

Go deeper

The three acts above are free. The paper-by-paper list and the genetics findings are part of the Research plan.
Research planResearch access

Every study and gene finding

Open the strongest papers with their populations and findings, and the gene differences human studies measured.

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On the evidence map →

Each marker shows the strongest record in the dossier. Records are extracted from published studies by a model pipeline and graded A to D; records whose own notes say no usable human data exists count as no result yet. Research summaries for education, not medical advice. How this page is sourced