Hemoglobin

Meta-analysis or review · Moderate effect · 216 studies linked

Studied in: Perioperative, CKD, Heart failure, Obstetric

Griffin 1999 RCT (n=78, preterm <1800 g): No significant Hgb difference between high-iron preterm formula (0.9 mg/dL) and standard term formula (0.5 mg/dL) at 6 months corrected age (p=0.391). Null finding within this population — higher iron fortification level did not improve hemoglobin. This does NOT contradict t...

• Safety and efficacy of intravenous iron therapy in reducing requirement for allogeneic blood transfusion: systematic review and meta-analysis of randomised clinical trials (2013)
• Effects of iron supplementation on cognitive development in school-age children: Systematic review and meta-analysis. (2016)
• Micronutrient supplementation in preterm infants: a randomized trial of two iron doses (1999)
• Efficacy of oral vs. intravenous iron for the treatment of iron deficiency anemia in different conditions: A systematic review and meta-analysis. (2026)
• Efficacy and safety of intravenous iron supplementation for perioperative iron deficiency anemia: a systematic review and network meta-analysis of randomized controlled trials. (2026)
• Interventions to Treat Pediatric Iron Deficiency Anemia: A Systematic Review and Meta-Analysis. (2026)
• +210 more studies

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

• Effect of l-carnitine supplementation on renal anemia in patients on hemodialysis: a meta-analysis (2021)
• The effects of L-carnitine in children with kidney failure undergoing dialysis: a systematic review. (2026)
• Carnitine supplements for people with chronic kidney disease requiring dialysis. (2022)
• Effects of L-carnitine supplementation in maintenance hemodialysis patients: a systematic review. (2002)
• Effects of Oral L-Carnitine Supplementation on Lipid Profile, Anemia, and Quality of Life in Chronic Renal Disease Patients under Hemodialysis: A Randomized, Double-Blinded, Placebo-Controlled Trial (2012)
• L-carnitine supplementation improves hematological pattern in patients affected by HCV treated with Peg interferon-α 2b plus ribavirin. (2011)
• +14 more studies

Meta-analysis or review · 20 studies linked

Studied in: Iron deficiency anemia, Hemodialysis

157 studies in corpus. Hemoglobin increase is secondary to enhanced iron absorption (vc_m9) in iron-deficient populations, not a direct hematopoietic effect. Meta-analyses in hemodialysis patients show improved erythropoietin responsiveness with adjunctive vitamin C.

• Treatment efficacy of vitamin C or ascorbate given as co-intervention with iron for anemia – A systematic review and meta-analysis of experimental studies (2023)
• Protective role of nigella sativa oil and vitamins C and E against aflatoxin M (2025)
• Ascorbic Acid Reduces the Blood Boss After Total Knee Arthroplasty: Insights From a Randomized Controlled Trial (2025)
• A randomized trial of once daily versus twice daily dosing of oral iron in CKD. (2023)
• Enhancing Supplemental Effects of Acute Natural Antioxidant Derived from Yeast Fermentation and Vitamin C on Sports Performance in Triathlon Athletes: A Randomized, Double-Blinded, Placebo-Controlled, (2023)
• Comparison of Ferric Sodium EDTA in Combination with Vitamin C, Folic Acid, Copper Gluconate, Zinc Gluconate, and Selenomethionine as Therapeutic Option for Chronic Kidney Disease Patients with Improv (2022)
• +14 more studies

Meta-analysis or review · 4 studies linked

Studied in: Stressed adults, Athletes, Iron deficient populations

• Effects of Withania somnifera (Ashwagandha) on Hematological and Biochemical Markers, Hormonal Behavior, and Oxidant Response in Healthy Adults: A Systematic Review. (2023)
• Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial. (2015)
• The role of Ashwagandha in modulating gut parameters in dogs-a randomized double-blind placebo-controlled trial. (2024)
• Efficacy and safety of Ashwagandha ( (2026)

Human trials · 3 studies linked

• Effects of resistance-based training and polyphenol supplementation on physical function, metabolism, and inflammation in aging individuals. (2026)
• Acute hematological, metabolic, and inflammatory responses to simulated-6000 ft masked versus unmasked high-intensity interval training in youth soccer players: a randomized crossover pilot study. (2025)
• Evaluating the impact of coenzyme Q10 and high-intensity interval training on lactate threshold and Plasma blood gases in rats: a randomized controlled trial. (2025)

Meta-analysis or review · 3 studies linked

Studied in: Adults

43 corpus studies but no extracted RCT endpoint data for resveratrol effect on hemoglobin. Gap.

• Foetal haemoglobin inducers for reducing blood transfusion in non-transfusion-dependent beta-thalassaemias. (2023)
• Efficacy and safety of resveratrol, an oral hemoglobin F-augmenting agent, in patients with beta-thalassemia intermedia. (2018)
• Effects of resveratrol on cerebral blood flow variables and cognitive performance in humans: a double-blind, placebo-controlled, crossover investigation. (2010)

Human trials · 2 studies linked

Studied in: Adults overweight obese, European finnish

Authors attributed to repeated blood draws rather than true adverse hematologic effect

• Nicotinamide riboside improves muscle mitochondrial biogenesis, satellite cell differentiation, and gut microbiota in a twin study (2023)
• Association between blood nicotinamide adenine dinucleotide levels and blood laboratory parameters at baseline and after nicotinamide mononucleotide supplementation in middle-aged healthy individuals: (2025)

Human trials · 2 studies linked

Studied in: Deficient baseline, Iron deficiency anemia

• Maternal prenatal, with or without postpartum, vitamin D3 supplementation does not improve maternal iron status at delivery or infant iron status at 6 months of age: secondary analysis of a randomised (2023)
• The effect of high-dose vitamin D supplementation on hepcidin-25 and erythropoiesis in patients with chronic kidney disease (2023)

Human trials · 1 study linked

Studied in: No human data

• A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood. (2015)

Human trials · 1 study linked

26 studies mention hemoglobin but not as primary endpoint. No evidence for clinically meaningful hemoglobin effect.

• A randomized, double blinded, placebo-controlled clinical trial of silymarin in ulcerative colitis (2012)

Human trials · 1 study linked

Studied in: No human data

• Effects of Antioxidant Supplements (BioPQQ™) on Cerebral Blood Flow and Oxygen Metabolism in the Prefrontal Cortex. (2016)

Human trials · 1 study linked

• The discovery of berberine erythrocyte-hemoglobin self-assembly delivery system: a neglected carrier underlying its pharmacokinetics. (2022)

Human trials · 0 studies linked

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

Studied in: General adult, Healthy adult

Meta-analysis or review · 12 studies linked

Studied in: Adults, High dose zinc, CKD

SAFETY: Chronic zinc >40 mg/d can cause copper-deficiency anemia manifesting as hemoglobin reduction. At standard supplementation doses (15–30 mg/d), hemoglobin not significantly affected in non-anemic adults. Some pediatric deficiency-correction studies show modest hemoglobin improvement.

• Effect of oral zinc regimens on human hepatic copper content: a randomized intervention study (2022)
• Zinc-Induced Copper Deficiency Myeloneuropathy Masquerading as Paraneoplastic Syndrome: A Case Report. (2025)
• Antioxidant supplementation for sickle cell disease. (2024)
• Childhood stunting and micronutrient status unaffected by RCT of micronutrient fortified drink (2021)
• Daily consumption of ready-to-use peanut-based therapeutic food increased fat free mass, improved anemic status but has no impact on the zinc status of people living with HIV/AIDS: a randomized contro (2016)
• Zinc finger nuclease-mediated gene editing in hematopoietic stem cells results in reactivation of fetal hemoglobin in sickle cell disease. (2024)
• +6 more studies

Meta-analysis or review · 9 studies linked

Studied in: Thalassemia, Sickle cell, Hemodialysis

VE may modestly improve hemoglobin in hemolytic anemias (thalassemia, sickle cell) by protecting RBC membranes. Not a primary hematopoietic effect. Insufficient pooled data for direction assignment in general population.

• Measures of cellular oxidative damage following vitamin E supplementation in young patients with transfusion-dependent thalassemia: a double-blind randomized controlled trial. (2025)
• Oxidative stress markers and tissue iron overload after 12-months vitamin E supplementation for children with transfusion-dependent β-thalassemia on different iron chelators: A randomized placebo-cont (2025)
• Effects of three months of treatment with vitamin E and N-acetyl cysteine on the oxidative balance in patients with transfusion-dependent β-thalassemia. (2021)
• Effects of supplemental Bacillus subtilis, injectable vitamin E plus selenium, or both on health parameters during the transition period in dairy cows in a tropical environment. (2021)
• Investigating the effects of vitamins E and C on oxidative stress and hematological parameters among power plant workers: A double-blind randomized controlled clinical trial. (2020)
• N-Acetylcysteine supplementation reduces oxidative stress and DNA damage in children with β-thalassemia. (2014)
• +3 more studies

Meta-analysis or review · Negligible effect · 5 studies linked

Studied in: Adult, General

• Weight loss induced by a hypocaloric diet with or without fish oil supplementation re-established iron and omega-3 fatty acid homeostasis in middle-aged women with obesity: A post-hoc analysis of a ra (2024)
• Effects of omega-3 fatty acids supplementation on perioperative blood loss and complications after radical prostatectomy. (2022)
• Supplementation with oil rich in eicosapentaenoic acid, but not in docosahexaenoic acid, improves global cognitive function in healthy, young adults: results from randomized controlled trials. (2021)
• Safety and tolerability of prescription omega-3 fatty acids: A systematic review and meta-analysis of randomized controlled trials. (2018)
• Effect of fish oil supplement in maintenance hemodialysis patients: a systematic review and meta-analysis of published randomized controlled trials (2015)

Meta-analysis or review · 1 study linked

43 studies reference hemoglobin. No MA-level data for direct melatonin effect.

• Efficacy and Safety of Preoperative Melatonin for Women Undergoing Cesarean Section: A Systematic Review and Meta-Analysis of Randomized Placebo-Controlled Trials. (2023)

3 studies linked

Studied in: Healthy adults

Hemoglobin concentration not significantly altered; no erythropoietic mechanism

• Differential response of muscle phosphocreatine to creatine supplementation in young and old subjects. (2002)
• Effect of sulphurous mineral water in haematological and biochemical markers of muscle damage after an endurance exercise in well-trained athletes. (2014)
• The influence of midsole cushioning on mechanical and hematological responses during a prolonged downhill run. (2002)

Human trials · 2 studies linked

Studied in: Adults

Mg not a direct erythropoietic factor; hemoglobin unaffected in supplementation trials.

• The effect of magnesium sulfate on post off-pump coronary artery bypass grafting bleeding. (2016)
• Magnesium-gallate MOF integrated conductive cryogel for inflammation regulation and boosting bone regeneration. (2025)

Human trials · Negligible effect · 2 studies linked

Studied in: Adult

• N-acetylcysteine modulates markers of oxidation, inflammation and infection in tuberculosis. (2025)
• Effects of three months of treatment with vitamin E and N-acetyl cysteine on the oxidative balance in patients with transfusion-dependent β-thalassemia. (2021)

Human trials · 2 studies linked

Studied in: Burn patients, Critically ill

• Coenzyme Q10 supplementation in burn patients: a double-blind placebo-controlled randomized clinical trial (2024)
• Beneficial Effect of Ubiquinol on Hematological and Inflammatory Signaling during Exercise. (2020)

Meta-analysis or review · 3 studies linked

Studied in: Adults PCOS, Adults T2DM, Adults elderly

• High-intensity interval training versus moderate-intensity continuous training for polycystic ovary syndrome: a meta-analysis of randomized controlled trials. (2025)
• The effects of high-intensity interval training versus moderate-intensity continuous training on athletes' aerobic endurance performance parameters. (2024)
• Comparison of Three Popular Exercise Modalities on V˙O2max in Overweight and Obese. (2016)