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01A1c · the three-month number

Sugarleaves amark

Glucose sticks to hemoglobin at a rate that tracks your blood sugar, and it stays for the life of the red cell. Your A1c is the share that has been marked.

Measured in
Blood
Units
%, mmol/mol
Also called
A1c, glycated hemoglobin, glycohemoglobin
Human deoxyhemoglobin (PDB 4HHB), rendered from its atomic coordinates.
Human deoxyhemoglobin · PDB 4HHB

AWhat moves HbA1c

24 of 27 studied

In human studies, 19 of the 27 supplements and practices researched so far lowered HbA1c. 5 showed no change. 3 were never studied for it.
  • Supported 19
  • No effect 5
  • Conflicting 0
  • Not studied 3
See HbA1c on the evidence map →Check claims about HbA1c →

Moves it19

Human studies found a change. The grade reflects the studies behind it, from A (strongest) to D.

HIITLowersGrade A

HIIT lowers HbA1c.

Meta-analysis or review · 40 studies linked

Studied in: T2DM, Prediabetes, Overweight obese, Asian dominant RCTS

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ResveratrolLowersGrade A

Resveratrol lowers HbA1c.

Meta-analysis or review · Small effect · 26 studies linked

Studied in: T2DM, Prediabetes, Adults

Not assessed in timmers_2011 (30-day intervention too short for HbA1c change)

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BerberineLowersGrade A

Berberine lowers HbA1c.

25 studies linked

Studied in: T2DM, Predominantly Chinese RCTS, Duration typically 8 to 16 weeks, NOT prediabetes confirmed

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MagnesiumLowersGrade A

Magnesium lowers HbA1c.

Meta-analysis or review · Small effect · 22 studies linked

Studied in: T2DM, Prediabetes

HbA1c reduction modest but consistent; larger effect in baseline HbA1c >8%.

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ZincLowersGrade A

Zinc lowers HbA1c.

Meta-analysis or review · 22 studies linked

Studied in: T2D, Adults, Global

Clinically modest but statistically significant. Strongest in baseline HbA1c >8%. Effect in prediabetes and healthy adults not established. Confounding from concomitant lifestyle changes in open-label trials.

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Vitamin D3LowersGrade A

Vitamin D3 lowers HbA1c.

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

Studied in: Prediabetes, Deficient baseline, Overweight obese, European

Grade corrected from B to A. Mirhosseini 2018 MA (grade A, -0.22%, p=0.01) plus Pittas 2023 IPD-MA corroboration. Significant with ≥12 weeks supplementation.

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L-carnitineLowersGrade 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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Vitamin CLowersGrade A

Vitamin C lowers HbA1c.

Meta-analysis or review · 15 studies linked

Studied in: Adults, Type 2 diabetes, Elevated hba1c

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Zone 2 cardioLowersGrade A

Zone 2 cardio lowers HbA1c.

Meta-analysis or review · 15 studies linked

Studied in: Adults T2DM, Adults prediabetes

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MelatoninLowersGrade A

Melatonin lowers HbA1c.

Meta-analysis or review · Small effect · 14 studies linked

Studied in: Adults, T2DM

Marginal HbA1c reduction; do not present as clinically meaningful without context

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Milk thistleLowersGrade A

Milk thistle lowers HbA1c.

Meta-analysis or review · Small effect · 14 studies linked

Studied in: Type 2 diabetes, NAFLD with diabetes

HbA1c reduction modest and primarily demonstrated in T2DM populations with concurrent NAFLD. Unlikely to be clinically meaningful as glycemic monotherapy. Adjunctive role in metabolic liver disease; not a standalone diabetes treatment.

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TaurineLowersGrade A

Taurine lowers HbA1c.

Meta-analysis or review · 7 studies linked

Studied in: Type 2 diabetes, Metabolic syndrome, Adults

18 corpus studies. Direction confirmed by ≥2 MAs. Magnitude requires MA outcome extraction.

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IronLowersGrade A

Iron lowers HbA1c.

Meta-analysis or review · Small effect · 6 studies linked

Studied in: Ida diabetic, Ida non diabetic

CONTESTED/ARTEFACTUAL: Iron deficiency falsely elevates HbA1c by prolonging RBC lifespan and increasing glycation time. Iron repletion normalises RBC lifespan, reducing HbA1c by 0.5–1.0% independently of glycemic change. This is a measurement artefact, not a true glycemic effect. Clinicians must account for this whe...

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Ubiquinol (CoQ10)LowersGrade A

Ubiquinol (CoQ10) lowers HbA1c.

Meta-analysis or review · 6 studies linked

Studied in: Type 2 diabetes

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CreatineLowersGrade B

Creatine lowers HbA1c.

Meta-analysis or review · Small effect · 7 studies linked

Studied in: Metabolic syndrome, Type2 diabetes

Delpino 2022 MA: HbA1c reduction with creatine, particularly with concurrent exercise training. Effect in normoglycemic populations unclear. Duration of included trials generally 8–12 weeks; longer-term glycemic benefit not established.

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Finnish saunaLowersGrade B

Finnish sauna lowers HbA1c.

Meta-analysis or review · 2 studies linked

Studied in: Type 2 diabetes, Insulin resistant

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Red yeast riceLowersGrade B

Red yeast rice lowers HbA1c.

Human trials · 2 studies linked

Studied in: T2DM, Hyperlipidemia, Chinese

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AshwagandhaLowersGrade B

Ashwagandha lowers HbA1c.

Meta-analysis or review · 1 study linked

Studied in: Type2 diabetes, Predominantly Indian cohorts, Not established in normoglycemic

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Vitamin K2LowersGrade B

Vitamin K2 lowers HbA1c.

Small effect · 1 study linked

Studied in: Type2 diabetes, Asian

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Studied, no change5

Studies looked and found no meaningful change. That is a result, not missing data.

Vitamin ENo changeGrade A

Studies of Vitamin E found no change in HbA1c.

21 studies linked

Studied in: T2DM, Adult, Mixed sex

VE-MA-003 (MA of 14 RCTs, n=714): WMD −0.12% (95% CI −0.31 to +0.07), non-significant. Grade A null finding from well-powered MA. VE is not a glycemic control intervention.

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Omega-3No changeGrade A

Studies of Omega-3 found no change in HbA1c.

Negligible effect · 16 studies linked

Studied in: T2DM, Prediabetes, General adult

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NACNo changeGrade B

Studies of NAC found no change in HbA1c.

Human trials · 2 studies linked

Studied in: PCOS, Adult

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NAD+No changeGrade B

Studies of NAD+ found no change in HbA1c.

Human trials · 2 studies linked

Studied in: Adults overweight obese, European finnish, Mean age 40

Overall HbA1c within normal range throughout. Subgroup divergence (lean vs heavy) warrants attention in future trials.

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L-theanineNo changeGrade B

Studies of L-theanine found no change in HbA1c.

Human trials · 1 study linked

Studied in: Elderly japanese, Green tea mixture not pure ltheanine

Same grade inconsistency as fasting_glucose. Recommend same grade_adjustment_reason field.

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Not studied3

No usable human study has measured HbA1c with these. A gap is not a negative result: nobody has looked.

CollagenLion's manePQQ

Commission research on a gap →

BThe molecule

Human deoxyhemoglobin

  1. Human deoxyhemoglobin, whole structure.

    01Four chains, four hemes. Hundreds of millions of these fill every red cell.

  2. Human deoxyhemoglobin, cut-away view.

    02Look through it: the coral atoms are β-chain valine 1, where the glucose that A1c counts attaches.

  3. Human deoxyhemoglobin, close-up.

    03This is the site the A1c test counts. It changes slowly, which is why A1c averages months, not mornings.

Structure: PDB 4HHB · X-ray 1.74 Å · Fermi, Perutz, Shaanan & Fourme, 1984. Rendered from atomic coordinates in Blender; 4,556 atoms, about 7.5 nm across.

Why trials measure it. Trials use it to see whether an intervention changed average blood sugar across the study, not just on one morning.

About this marker: Hemoglobin A1C (HbA1c) Test (MedlinePlus, U.S. National Library of Medicine).

Evidence states come from published human studies found in PubMed and OpenAlex and read by a model pipeline. "Not studied" means no usable human study was found for this marker, which is a gap, not a negative result. Every result links its studies so you can check it.

Research summary for education. Not medical advice.