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Research ·

Berberine vs metformin: the trials side by side

Qaytona Team · 6 min read

A woman reading in a teal lounge chair by a window, with ferns growing across the floor in front of her.

Image by Casey Stolberg

Berberine lowers blood sugar, but by less than metformin, and with much less research behind it. In pooled placebo-controlled trials, berberine lowered glycated hemoglobin (HbA1c) by about 0.4 percentage points. Metformin lowered it by about 1.1. No berberine trial has run long enough to show fewer complications or deaths, which metformin showed over ten years. Patients often ask about adding it to metformin, so the useful questions are what berberine adds and what to check first.

Side by side

BerberineMetformin
HbA1c drop against placeboAbout 0.4 points, 20 trialsAbout 1.1 points, 35 trials
Added to other diabetes drugsAbout 0.7 points, 50 trialsAbout 1.0 point, added to oral drugs
Head to head, 1.5 g a day each, 3 months9.5% to 7.5%9.2% to 7.7%
Longest trials1 to 3 months for mostA median of 10.7 years
Fewer complications or deathsNot studied36% fewer deaths in overweight adults
Sold asDietary supplementPrescription drug

The columns come from different sets of trials, so read the gap as approximate. Berberine's placebo figure pools adults with and without diabetes, and the effect was larger in those with diabetes. Nearly all its trials ran in China.

Metformin's figures pool trials of at least 12 weeks in people with diabetes.

The only head-to-head trial is small. It gave 500 mg of berberine or metformin three times a day for three months to adults with newly diagnosed type 2 diabetes, and 15 finished on berberine and 16 on metformin.

Metformin's long-term record comes from the UK Prospective Diabetes Study. Overweight adults with new type 2 diabetes who were assigned metformin had 36% fewer deaths from any cause than those on diet alone, over a median of 10.7 years.

Taking both

Added to metformin and other diabetes drugs, berberine lowered HbA1c by another 0.69 points in pooled trials, though results varied widely. Most trials used 0.9 to 1.5 g a day for one to three months.

Stomach effects are the common problem. In Yin's studies, 34.5% had diarrhea, constipation, gas or abdominal pain, mostly in the first four weeks. Fourteen people cut the dose to 300 mg three times a day, and 10 of them were also taking metformin or acarbose. The authors suggest the lower dose alongside those drugs.

Pooled trials found no rise in low blood sugar, but the trials were short.

We found no human study of purified berberine's effect on metformin levels. Goldenseal, an herb that contains berberine, lowered them by about 20% at low metformin doses and not at high ones.

The "nature's Ozempic" claim

The nickname comes from social media. Of 170 berberine products in the NIH supplement label database, only one mentions GLP-1, and none mention Ozempic or semaglutide.

No trial has compared berberine with semaglutide or tirzepatide. Across 23 randomized trials, berberine lowered body weight 0.88 kg more than control.

In the trial behind semaglutide's approval for weight loss, adults lost 15.3 kg over 68 weeks, against 2.6 kg on placebo. The trials enrolled different people for different lengths of time, so the comparison is rough, but it isn't close.

Before recommending it

  • Diabetes medicines. Berberine lowers glucose on top of insulin or a sulfonylurea, so check glucose more often in the first weeks.
  • Other medicines. Two weeks of 300 mg three times a day slowed three liver enzymes that clear many drugs: cytochrome P450 3A4, 2D6 and 2C9.
  • Transplant drugs. In kidney transplant patients, 200 mg three times a day raised cyclosporine levels.
  • Pregnancy and breastfeeding. Avoid it. The National Center for Complementary and Integrative Health advises against goldenseal, which contains berberine, during pregnancy and breastfeeding.
  • Newborn jaundice. In lab and rat studies, berberine pushed bilirubin off albumin, a risk for brain injury in jaundiced newborns.
  • The product. Of 155 products that state an amount, two-thirds reach the 900 to 1,500 mg a day most trials used. But 54% say to take the whole day's amount at once, where the trials split it into two or three doses with meals. 37% add other active ingredients, most often chromium or cinnamon, and only 16% mention diabetes, insulin or blood sugar in their warnings.

The berberine monograph covers the other uses studied, the forms on the market and its interactions.

Sources

  1. 1Zhao et al., 2023PubMed20 placebo-controlled trials, 1,761 adults. HbA1c fell 4.48 mmol/mol, about 0.4 percentage points. Effects were larger in people with diabetes and in Asian populations.
  2. 2Hirst et al., 2012PubMed35 trials. Metformin alone lowered HbA1c 1.12 points against placebo, and 0.95 points when added to other oral drugs. Higher doses lowered it more.
  3. 3Yin et al., 2008PubMed CentralTwo 3-month pilot studies in Shanghai using berberine hydrochloride. Funded by Xinhua Hospital and partly by an NIH grant.
  4. 4UKPDS 34, 1998PubMed753 overweight adults with newly diagnosed type 2 diabetes. Metformin cut diabetes-related endpoints by 32% and all-cause deaths by 36% against diet alone.
  5. 5Wang et al., 2024PubMed Central50 randomized trials, 4,150 adults with type 2 diabetes. One trial ran in Iran and the rest in China.
  6. 6Xie et al., 2022PubMed Central37 randomized trials, 3,048 adults with type 2 diabetes. Hypoglycemia was not more common: relative risk 0.48, 95% confidence interval 0.21 to 1.08.
  7. 7Nguyen et al., 2025PubMed CentralOpen-label crossover in adults with type 2 diabetes taking metformin. Exposure fell about 20% at 500 to 750 mg a day and not at all at 2,000 mg or more.
  8. 8Elahi Vahed et al., 2026PubMed23 randomized trials in adults. Weight fell 0.88 kg more than with control. The authors call for better reporting of berberine purity and dose.
  9. 9STEP 1, 2021PubMed1,961 adults with obesity and no diabetes took weekly semaglutide 2.4 mg or placebo for 68 weeks. Weight fell 15.3 kg against 2.6 kg. Funded by Novo Nordisk.
  10. 10Guo et al., 2012PubMed CentralCrossover study in 17 healthy Chinese men. Midazolam exposure rose 40% after 2 weeks of berberine. Funded by NIH and Chinese government grants.
  11. 11Wu et al., 2005PubMed52 kidney transplant recipients took berberine with cyclosporine for 3 months. Cyclosporine trough levels ended 29% higher than in 52 who did not take it.
  12. 12NCCIHNCCIHPregnant or breastfeeding women should not use goldenseal, and its berberine can be harmful to newborns. Last updated February 2025.
  13. 13Chan, 1993PubMedBerberine displaced bilirubin from albumin about ten times more strongly than phenylbutazone in the lab, and raised unbound bilirubin in rats.
  14. 14NIH Dietary Supplement Label DatabaseNIH label databaseSearched October 7, 2026: 221 on-market labels with berberine in the name, reduced to 170 products, newest label each. 155 state a berberine amount.