Blood sugar supplements share a short list of popular ingredients. Some have a reasonable amount of human research; others ride on tradition or test-tube studies. Below, we rank the ingredients that have pages on CapsReview by the strength of human evidence for blood sugar markers such as fasting glucose, post-meal glucose and A1C. Even the top entries have limited evidence, and none treats or prevents diabetes. The National Center for Complementary and Integrative Health (NCCIH) puts it plainly: there is weak evidence of possible benefit for a few supplements, and none should replace medical treatment.
How we ranked them
We prioritized systematic reviews and randomized, placebo-controlled trials in people, then considered study size, consistency and whether results came from people with normal, borderline or diagnosed high blood sugar. Animal and laboratory findings did not count toward the ranking.
1. Berberine
What it is: a yellow compound found in plants such as goldenseal, barberry and tree turmeric. What studies show: NCCIH describes a 2021 review of 46 studies with 4,158 participants suggesting berberine may lower blood glucose and insulin resistance in people with type 2 diabetes, though most studies were in China, results varied and some were of poor quality. Typical studied dose: 200 to 1,000 mg two to three times daily. Cautions: digestive side effects, drug interactions, and it must not be used in pregnancy, breastfeeding or infants. Read more about berberine.
2. Chromium
What it is: an essential trace mineral that helps insulin work. What studies show: according to NCCIH, a 2022 review of 16 studies (868 participants) suggested chromium may improve HbA1c, fasting glucose and insulin resistance in type 2 diabetes. Typical studied dose: about 200 to 1,000 mcg per day, versus an Adequate Intake of 20 to 35 mcg listed by the Office of Dietary Supplements. Cautions: may raise the risk of hypoglycemia with insulin or other diabetes medicines and can reduce levothyroxine absorption. See chromium.
3. Cinnamon
What it is: a common spice from Cinnamomum bark. What studies show: NCCIH cites a 2019 review of 16 studies (1,098 participants) finding reductions in fasting glucose and insulin resistance in prediabetes and type 2 diabetes, but its cinnamon fact sheet concludes it is unclear whether cinnamon helps because studies often fail to specify the species or plant part. Typical studied dose: varies widely; doses below 6 grams per day do not appear to pose a health risk. Cautions: cassia cinnamon contains coumarin, a concern for people with liver disease. See cinnamon.
4. Gymnema
What it is: an Ayurvedic climbing vine whose leaves blunt sweet taste. What studies show: a 2021 meta-analysis of 10 studies in type 2 diabetes reported lower fasting glucose and A1C, but compared results with baseline rather than placebo. A small placebo-controlled trial in 30 adults with impaired glucose tolerance found lower two-hour glucose and A1C after 12 weeks. Typical studied dose: about 400 to 600 mg per day. Cautions: may add to diabetes medicines; LiverTox notes rare, weakly attributed liver injury reports. See gymnema.
5. Korean (Asian) ginseng
What it is: the root of Panax ginseng. What studies show: NCCIH notes a 2022 review of 20 studies (1,295 participants) that found improvements in cardiometabolic factors, including fasting glucose, in people with prediabetes and diabetes, but calls the overall evidence on blood sugar control inconclusive and conflicting. Typical studied dose: varies by preparation. Cautions: insomnia is the most common side effect; long-term safety is uncertain and it is not advised in pregnancy. See Korean ginseng.
6. Maqui berry
What it is: a Chilean berry rich in delphinidins. What studies show: a small placebo-controlled crossover study found lower post-meal glucose after rice, and a three-month study without placebo in 31 people with glucose intolerance saw A1C fall from 5.65% to 5.35%. The trials are small and some were industry-funded. Typical studied dose: 180 mg per day of a standardized extract. Cautions: few safety data beyond short studies. See maqui berry.
7. Grape seed extract
What it is: a proanthocyanidin-rich extract from wine grape seeds. What studies show: a meta-analysis of 50 trials found a small drop in fasting glucose (about 2 mg/dL) with no change in HbA1c; NCCIH notes stronger data for cholesterol and diastolic blood pressure. Typical studied dose: roughly 100 to 300 mg per day. Cautions: generally well tolerated; check with a doctor if you take prescription medicines. See grape seed extract.
8. Biotin
What it is: vitamin B7. What studies show: evidence comes mainly from a trial combining 2 mg biotin with 600 mcg chromium in 447 people with poorly controlled type 2 diabetes, which lowered A1C by 0.54% versus placebo. There is little evidence for biotin alone. Typical studied dose: 2 mg with chromium. Cautions: high doses can cause falsely high or low lab results, including thyroid and troponin tests, according to the Office of Dietary Supplements and FDA. See biotin.
9. Alpha-lipoic acid
What it is: an antioxidant compound made in the body and sold as a supplement. What studies show: NCCIH reports that a 2019 review of 10 studies found alpha-lipoic acid was no better than placebo for blood sugar or blood lipids in type 2 diabetes, although some research suggests it may help nerve pain. Typical studied dose: 600 mg per day in many trials. Cautions: headache, heartburn and nausea are the most common side effects. See alpha-lipoic acid.
Ingredients with little or no blood sugar evidence
Many formulas pad their labels with ingredients that have essentially no human glucose research, including maca, eleuthero, African mango, Coleus forskohlii, guarana, juniper berry, manganese and licorice root. A meta-analysis of capsaicin trials also found no meaningful effect of cayenne‘s active compound on glucose or insulin. Their presence is not a reason to choose a product, and licorice and guarana bring their own safety concerns.
How to use this list
Use the ranking to judge labels, not to self-treat. A formula built on the top ingredients at disclosed, studied doses is more credible than one with dozens of extras. But lifestyle steps, including regular activity, a fiber-rich diet, enough sleep and weight management, have stronger evidence than any of these ingredients. If you take insulin or other glucose-lowering medicines, talk to your doctor before adding any supplement, since several ingredients above can increase the risk of hypoglycemia. For product rankings, see our guide to the best blood sugar support supplements.
How we ranked these
We ranked ingredients by human evidence for glucose markers, giving most weight to systematic reviews and placebo-controlled trials and summaries from NCCIH and the NIH Office of Dietary Supplements. Animal and lab studies did not count toward the ranking.
Read our full review method