Best Supplements for Reduced Fasting Blood Glucose Levels
Ranked by research evidence. Compare 126 supplements across 193 papers from the biomedical literature, with effect direction, evidence strength, and dose range for each.
Top picks by evidence
- High evidence8 studies
Across 8 studies, 7 reported beneficial effects of black cumin (Nigella sativa) on reducing fasting blood glucose levels, with effect sizes ranging from small to large. The most robust evidence comes from meta-analyses and RCTs, including a large 2025 meta-analysis (n=5026) that found moderate beneficial effects, while several recent meta-analyses reported large effect sizes in clinical populations such as those with type 2 diabetes or metabolic syndrome. The median study duration was 32 days, with doses reported in two studies ranging from 200 to 4600 mg/day.
Dose: 200 to 4600 mg/day (based on 2 of 8 studies reporting dose) - High evidence7 studies
Across 7 studies, all reported beneficial effects of L-carnitine on reducing fasting blood glucose, with predominantly small effect sizes. The evidence includes multiple meta-analyses and randomized controlled trials in clinical populations such as PCOS, overweight/obesity, and hemodialysis. Effects were typically observed at 8 weeks, with most doses converging around 2000–3000 mg/day in adults.
Dose: 2000–3000 mg/day (adults); 50 mg/kg/day (pediatric) - High evidence5 studies
Across 5 studies, all reported beneficial effects on reducing fasting blood glucose, with effect sizes ranging from small to large. The evidence includes multiple meta-analyses showing statistically significant reductions (e.g., MD = -11.48 mg/dL, MD = -6.30 mg/dL). Most studies focused on adults with type 2 diabetes or related metabolic conditions. Doses and forms were not consistently reported, so typical dosing cannot be determined.
126 supplements
- HighBlack CuminAcross 8 studies, 7 reported beneficial effects of black cumin (Nigella sativa) on reducing fasting blood glucose levels, with effect sizes ranging from small to large. The most robust evidence comes from meta-analyses and RCTs, including a large 2025 meta-analysis (n=5026) that found moderate beneficial effects, while several recent meta-analyses reported large effect sizes in clinical populations such as those with type 2 diabetes or metabolic syndrome. The median study duration was 32 days, with doses reported in two studies ranging from 200 to 4600 mg/day. · Dose: 200 to 4600 mg/day (based on 2 of 8 studies reporting dose)7 beneficial1 neutral8 studies
- HighL-CarnitineAcross 7 studies, all reported beneficial effects of L-carnitine on reducing fasting blood glucose, with predominantly small effect sizes. The evidence includes multiple meta-analyses and randomized controlled trials in clinical populations such as PCOS, overweight/obesity, and hemodialysis. Effects were typically observed at 8 weeks, with most doses converging around 2000–3000 mg/day in adults. · Dose: 2000–3000 mg/day (adults); 50 mg/kg/day (pediatric)7 beneficial7 studies
- HighTurmericAcross 5 studies, all reported beneficial effects on reducing fasting blood glucose, with effect sizes ranging from small to large. The evidence includes multiple meta-analyses showing statistically significant reductions (e.g., MD = -11.48 mg/dL, MD = -6.30 mg/dL). Most studies focused on adults with type 2 diabetes or related metabolic conditions. Doses and forms were not consistently reported, so typical dosing cannot be determined.5 beneficial5 studies
- HighCinnamonAcross 5 studies, 4 reported beneficial effects of cinnamon on reducing fasting blood glucose, with effect sizes ranging from moderate to large. The median study duration was 57 days (approximately 8 weeks), suggesting effects are typically observed at 8 weeks or longer. The most studied population is adults with type 2 diabetes, though doses varied widely (≤2 g/day to 600 mg/day) and were not consistently reported.4 beneficial1 neutral5 studies
- ModerateGardeniaAcross 4 studies, 3 reported beneficial effects of crocin (a constituent of Gardenia) on reducing fasting blood glucose (FBG) in clinical populations, with moderate effect sizes in two meta-analyses and a small effect in one review. One small RCT found no significant benefit. The median study duration was 56 days (reported in only 1 study), and the most studied population includes individuals with type 2 diabetes or metabolic syndrome. Evidence suggests a moderate beneficial effect, but the number of studies is small and the neutral RCT highlights potential heterogeneity.3 beneficial1 neutral4 studies
- ModerateSaffronAcross 4 studies (3 meta-analyses and 1 RCT), 3 reported beneficial effects of saffron supplementation on reducing fasting blood glucose (FBG), with predominantly small effect sizes. The most studied population was clinical (metabolic syndrome, type 2 diabetes, prediabetes), and the median study duration was 84 days (12 weeks), suggesting effects are typically observed at 12 weeks. The only study reporting a dose used 200 mg/day. · Dose: 200 mg/day3 beneficial1 neutral4 studies
- ModerateflaxseedAcross all 3 studies, flaxseed supplementation consistently showed a beneficial moderate-sized effect on reducing fasting blood glucose levels. The strongest evidence comes from a 90-day RCT using 16 g daily in adults with type 2 diabetes and a meta-analysis in patients with coronary artery disease. The median study duration was 90 days (reported in 1 of 3 studies).3 beneficial3 studies
- ModerateSesameAcross 3 studies (all meta-analyses or systematic reviews), sesame supplementation consistently showed beneficial large effects on reducing fasting blood glucose levels. All 3 studies reported statistically significant reductions, with effect sizes ranging from moderate to large. Effects were observed in populations with diabetes or elevated cardiometabolic risk, typically over 6 weeks.3 beneficial3 studies
- ModerateKonjacAcross 3 studies, all 3 reported beneficial effects of konjac (glucomannan) supplementation on reducing fasting blood glucose levels, with effect sizes ranging from small to large. The median study duration was 90 days, suggesting effects typically observed at 12+ weeks. Evidence comes primarily from clinical populations with type 2 diabetes or prediabetes, though doses varied and were not consistently reported.3 beneficial3 studies
- ModerateTaurineAcross 3 meta-analyses, all 3 reported statistically significant beneficial effects on fasting blood glucose, with effect sizes ranging from small to moderate. The most commonly studied dose was 3 g/day, and effects were observed in diverse populations including general adults, overweight/obese individuals, and those with long COVID. Study durations varied, with one trial lasting 5 days. · Dose: 3 g/day (range 0.5–6 g/day)3 beneficial3 studies
- LowOkraAcross 3 studies, all reported beneficial moderate-to-large effects of okra on reducing fasting blood glucose levels in individuals with prediabetes or type 2 diabetes. The most-studied dose is up to 3,000 mg/day, and the evidence is derived from systematic reviews and meta-analyses. However, the evidence base is small, and conclusions should be considered preliminary. · Dose: ≤3000 mg/day3 beneficial3 studies
- LowKefirAcross 3 meta-analyses, 2 reported a moderate beneficial effect of kefir on reducing fasting blood glucose, while 1 found no significant effect (small effect size). The evidence suggests a potential benefit, but the overall effect size is moderate and limited by the small number of studies and mixed results.2 beneficial1 neutral3 studies
- LowVitamin DAcross 6 studies, 1 reported a small beneficial effect of vitamin D on reducing fasting blood glucose, while 5 found neutral results. The beneficial effect was observed in patients with metabolic-associated fatty liver disease (MAFLD), but evidence in other populations (obese children, PCOS, type 2 diabetes) was neutral. Effects were typically observed at 84 days of supplementation, though median study duration was only reported in 1 of 6 studies.1 beneficial5 neutral6 studies