Best Supplements for Reduced Hemoglobin A1c
Ranked by research evidence. Compare 75 supplements across 110 papers from the biomedical literature, with effect direction, evidence strength, and dose range for each.
Top picks by evidence
- High evidence6 studies
Across 6 studies, 5 reported beneficial effects of black cumin (Nigella sativa) supplementation on reducing hemoglobin A1c (HbA1c), with effect sizes predominantly moderate. The strongest evidence comes from a large 2025 meta-analysis (n=5026) showing significant improvement, while other meta-analyses report moderate-to-large reductions. Doses ranged from 200 to 4600 mg/day, and effects were observed primarily in populations with type 2 diabetes or metabolic syndrome; study durations were limited in reporting, but one study lasted 7 days.
Dose: 200 to 4600 mg/day - Moderate evidence5 studies
Across 5 studies, 3 reported beneficial effects of cinnamon on reducing Hemoglobin A1c, with a predominant effect size of moderate. The most evidence-supported dose is ≤2 g/day, and effects were observed primarily in clinical populations with type 2 diabetes. Median study duration was 30 days, suggesting short-term effects may be detectable but longer-term data are limited.
Dose: ≤2 g/day - Moderate evidence3 studies
Across 3 studies, all reported beneficial effects of L-carnitine on reducing hemoglobin A1c, with predominantly small effect sizes. The most-studied dose range is 1-2 g/day, and the evidence primarily comes from adults with type 2 diabetes or impaired glucose tolerance.
Dose: 1-2 g/day
- HighBlack CuminAcross 6 studies, 5 reported beneficial effects of black cumin (Nigella sativa) supplementation on reducing hemoglobin A1c (HbA1c), with effect sizes predominantly moderate. The strongest evidence comes from a large 2025 meta-analysis (n=5026) showing significant improvement, while other meta-analyses report moderate-to-large reductions. Doses ranged from 200 to 4600 mg/day, and effects were observed primarily in populations with type 2 diabetes or metabolic syndrome; study durations were limited in reporting, but one study lasted 7 days. · Dose: 200 to 4600 mg/day5 beneficial1 neutral6 studies
- ModerateCinnamonAcross 5 studies, 3 reported beneficial effects of cinnamon on reducing Hemoglobin A1c, with a predominant effect size of moderate. The most evidence-supported dose is ≤2 g/day, and effects were observed primarily in clinical populations with type 2 diabetes. Median study duration was 30 days, suggesting short-term effects may be detectable but longer-term data are limited. · Dose: ≤2 g/day3 beneficial2 neutral5 studies
- LowTurmericAcross 4 studies, 3 reported beneficial effects (small to moderate) of turmeric/curcumin on reducing Hemoglobin A1c, and 1 study was neutral. The median study duration was 365 days, based on a single high-quality 12-month RCT using 1500 mg/day in adults with type 2 diabetes. Effect sizes were mixed (small to moderate) across studies. · Dose: 1500 mg/day3 beneficial1 neutral4 studies
- ModerateL-CarnitineAcross 3 studies, all reported beneficial effects of L-carnitine on reducing hemoglobin A1c, with predominantly small effect sizes. The most-studied dose range is 1-2 g/day, and the evidence primarily comes from adults with type 2 diabetes or impaired glucose tolerance. · Dose: 1-2 g/day3 beneficial3 studies
- LowVitamin DAcross 7 studies, 2 reported beneficial moderate-sized reductions in hemoglobin A1c, while 5 found neutral effects. The predominant effect size across studies is small to moderate, with the majority showing no significant impact. Most studies focused on clinical populations, including type 2 diabetes patients, but results were inconsistent and the median study duration was approximately 98 days (based on 2 studies).2 beneficial5 neutral7 studies
- LowGingerAcross 3 studies, 1 reported a beneficial moderate-sized effect on reducing hemoglobin A1c, while 2 found neutral effects (small effect size). The evidence base is too small to determine a most-studied dose, form, or population. The overall picture is mixed, with the only beneficial finding coming from a low-quality review, while two meta-analyses of higher quality found neutral results.1 beneficial2 neutral3 studies