Best Supplements for Reduced Fasting Blood Glucose Levels
Ranked by research evidence. Compare 111 supplements across 163 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 supplementation on fasting blood glucose levels, with effect sizes ranging from small to large (predominantly moderate-to-large). The highest-quality evidence, a 2025 meta-analysis of 82 RCTs involving 5,026 participants, found significant improvements in fasting blood sugar with doses from 200 to 4600 mg/day over a median study duration of 7 days. Effects were most pronounced in adults with type 2 diabetes or metabolic syndrome.
Dose: 200-4600 mg/day - High evidence5 studies
Across all 5 studies in the database, turmeric (curcumin) supplementation consistently reduced fasting blood glucose, with 5 of 5 studies reporting statistically significant beneficial effects. The predominant effect size was mixed (small to large), with meta-analyses reporting reductions ranging from -6.30 to -19.64 mg/dL. Studies primarily targeted clinical populations with type 2 diabetes or metabolic syndrome, and effects were observed across various curcumin formulations, though most trials did not provide specific dose or duration details.
- High evidence5 studies
Across all 5 studies in the database, L-carnitine supplementation consistently shows a beneficial effect on reducing fasting blood glucose levels, with all 5 studies reporting statistically significant reductions. Effect sizes are predominantly small (4 small, 1 moderate). The most commonly studied dose is ≥2000 mg/day, and effects have been observed in clinical populations including adults with PCOS and adults with overweight/obesity or impaired glucose tolerance. Median study duration is 42 days (based on one RCT), suggesting effects can appear within 6 weeks.
Dose: ≥2000 mg/day
- HighBlack CuminAcross 6 studies, 5 reported beneficial effects of black cumin supplementation on fasting blood glucose levels, with effect sizes ranging from small to large (predominantly moderate-to-large). The highest-quality evidence, a 2025 meta-analysis of 82 RCTs involving 5,026 participants, found significant improvements in fasting blood sugar with doses from 200 to 4600 mg/day over a median study duration of 7 days. Effects were most pronounced in adults with type 2 diabetes or metabolic syndrome. · Dose: 200-4600 mg/day5 beneficial1 neutral6 studies
- HighTurmericAcross all 5 studies in the database, turmeric (curcumin) supplementation consistently reduced fasting blood glucose, with 5 of 5 studies reporting statistically significant beneficial effects. The predominant effect size was mixed (small to large), with meta-analyses reporting reductions ranging from -6.30 to -19.64 mg/dL. Studies primarily targeted clinical populations with type 2 diabetes or metabolic syndrome, and effects were observed across various curcumin formulations, though most trials did not provide specific dose or duration details.5 beneficial5 studies
- HighL-CarnitineAcross all 5 studies in the database, L-carnitine supplementation consistently shows a beneficial effect on reducing fasting blood glucose levels, with all 5 studies reporting statistically significant reductions. Effect sizes are predominantly small (4 small, 1 moderate). The most commonly studied dose is ≥2000 mg/day, and effects have been observed in clinical populations including adults with PCOS and adults with overweight/obesity or impaired glucose tolerance. Median study duration is 42 days (based on one RCT), suggesting effects can appear within 6 weeks. · Dose: ≥2000 mg/day5 beneficial5 studies
- ModerateCinnamonAcross 4 out of 5 studies, cinnamon demonstrated beneficial effects on reducing fasting blood glucose levels, with effect sizes ranging from moderate to large. The highest-quality evidence comes from a meta-analysis of 3,054 adults with type 2 diabetes, finding a significant moderate reduction (WMD: -15.26 mg/dL; 95% CI: -22.23 to -8.30). Effects were typically observed after 30–84 days of supplementation, with doses of ≤2 g/day (including 600 mg/day) commonly studied in clinical populations with type 2 diabetes. · Dose: 600 mg to 2 g per day4 beneficial1 neutral5 studies
- ModerateOkraAcross all 3 studies, okra supplementation consistently shows beneficial and statistically significant reductions in fasting blood glucose levels. Effect sizes range from moderate to large, with mean reductions of approximately 15–40 mg/dL reported in meta-analyses of clinical populations (pre-diabetes and type 2 diabetes). The most-studied dose is ≤3,000 mg/day, but median study duration was not consistently reported. · Dose: ≤3,000 mg/day3 beneficial3 studies
- ModerateflaxseedAcross 3 studies, all reported beneficial moderate-sized effects on reducing fasting blood glucose levels. The only study reporting dosage used 16 g daily for 90 days. Effects were observed in clinical populations with Type 2 diabetes or coronary artery disease.3 beneficial3 studies
- LowKefirAcross 3 meta-analyses, 2 reported beneficial moderate-sized effects on reducing fasting blood glucose (FBS), while 1 found no significant effect. The beneficial studies observed reductions of approximately 8–10 mg/dL (p < 0.01), but the evidence base is small and no consistent dose or duration was reported.2 beneficial1 neutral3 studies
- LowGardeniaAcross 3 studies, 2 reported beneficial effects (1 moderate, 1 small) and 1 showed a neutral effect, suggesting a predominantly beneficial but mixed effect size for Gardenia (crocin) on reduced fasting blood glucose. The only study reporting a dose used 15 mg daily (two tablets), and the median duration among the single study reporting it was 56 days, indicating effects may be observed at approximately 8 weeks. All studies were in clinical populations (e.g., metabolic syndrome, type 2 diabetes), with meta-analytic evidence showing a moderate effect (FBG reduction of -14.10 mg/dL). · Dose: 15 mg daily (two tablets per day)2 beneficial1 neutral3 studies
- LowVitamin DAcross 6 studies, 5 found neutral small-sized effects of vitamin D supplementation on fasting blood glucose (FBG), and only 1 reported a statistically significant beneficial small-sized reduction. The single beneficial meta-analysis (2026) showed a small reduction in FBG in patients with MAFLD, but the evidence overall is predominantly neutral. Most studies were meta-analyses with short to moderate durations (median 84 days in one study), and no clear dose range or form emerged consistently across the included research.1 beneficial5 neutral6 studies