Berberine: benefits, side effects and what the regulators say

In the UK, the word "berberine" is typed into Google more than 100,000 times a month. Few things sold in capsules attract that much curiosity, and few come with such a divided file: genuine clinical trials on blood sugar on one side, and on the other a run of food safety agencies saying they cannot guarantee it is safe.

Both are true at once. Berberine does something, at doses where one agency says it behaves like a medicine, and it is still sold on the supplement shelf next to the vitamin C.

A yellow alkaloid, from barberry root to capsule

Berberine is a plant compound from the alkaloid family, vivid yellow, extracted mainly from the roots and bark of a handful of plants. The best known in Europe is the common barberry (Berberis vulgaris). Others include Indian barberry from the Himalayas, the goldthread used in Chinese medicine, and goldenseal from North America.

Barberries themselves, the sharp red berries scattered over Persian rice dishes, contain almost none. A capsule holds something else: a concentrated root extract, standardised to deliver several hundred milligrams of berberine, usually as the hydrochloride (the "HCl" on labels) or the sulphate.

In China it was given for infectious diarrhoea. It was while treating diarrhoea in patients with diabetes that doctors noticed their blood sugar falling, as the authors of a 2008 trial in The Journal of Clinical Endocrinology & Metabolism recall.

How berberine works, and why so little reaches the blood

Two lines of explanation dominate. The first plays out inside cells: berberine activates an enzyme called AMPK, which governs how the body uses glucose and fat, and it slows the liver's production of glucose. A 2020 review in Biomedicine & Pharmacotherapy sets out these mechanisms, most of them established in animals and in the laboratory.

The second plays out in the gut. Berberine crosses the intestinal wall very poorly: the studies cited by ANSES put its bioavailability at less than 1%. Most of the dose therefore stays in contact with the gut bacteria, which it alters. The PREMOTE trial, published in Nature Communications in 2020, links part of its effect on blood sugar to an action on intestinal bacteria and bile acids.

Blood sugar and cholesterol: the benefits of berberine on trial

The best-documented effects concern blood glucose and blood fats, in people who are unwell, over a few months.

The first row comes from a meta-analysis in the Endocrine Journal (2019), the next two from a pooled analysis in Frontiers in Nutrition (2022). PREMOTE, one of the few double-blind trials run across several centres, followed 409 people with newly diagnosed diabetes: over twelve weeks, HbA1c fell by about one point on berberine, against 0.6 of a point on placebo.

For cholesterol, it all began with a paper in Nature Medicine in 2004: 32 patients treated for three months, and LDL cholesterol down by a quarter.

Three caveats apply. Most of the trials were run in China, in patients with diabetes or raised blood fats, not in healthy adults. Almost all last three months. And there is a point of law: with no authorised health claim on the register, a manufacturer is not allowed to state that berberine acts on blood sugar. When the Advertising Standards Authority ruled against an advert for a berberine supplement in August 2025, one of its findings was that claims such as "supports blood sugar balance" were not authorised on the Great Britain register.

You will often read that berberine "works as well as metformin". The claim traces back to a 2008 pilot study in Metabolism: 36 patients, three months. A trial that size cannot support any conclusion of the kind, and ANSES points out that berberine interacts with metformin itself.

On weight, a slim effect

The pooled analyses disagree with one another, and the most favourable lands at around two kilos. Two meta-analyses published three months apart in 2020 reached opposite verdicts, one finding that reduction, the other no significant effect on weight at all. That is a long way from the claims made for it online, and it is the starting point of our article on natural Ozempic and what the studies say.

Why the "nature's Ozempic" label does not stick

The nickname comes from social media, and it misleads. Ozempic (semaglutide) is a molecule built to bind to the GLP-1 receptor and stay there for a week. Berberine does nothing of the sort. The work crediting it with an effect on GLP-1 release was done in diabetic rats, like the study in the Journal of Endocrinology in 2008. And no berberine trial comes close to the results of the obesity medicines.

The ASA took the same view from the advertising side. The advert it banned in 2025 presented a berberine supplement as a "natural GLP-1 secretion enhancer". The watchdog considered that this implied a comparison with prescription-only GLP-1 injections, which makes it a medicinal claim.

The ANSES opinion, point by point

The most detailed safety assessment to date is French. ANSES, the national food safety agency, was asked in April 2018 by the country's consumer protection directorate to look at the barberry supplements arriving on the market. Its opinion, signed on 1 August 2019 and made public that November, makes five findings.

The first concerns dose. The pharmacological effects of berberine are confirmed in the literature from 400mg a day in adults, and the experts do not rule them out at lower doses. The opinion lists them: effects on blood glucose and blood fats, on blood pressure and heart rate, on the nervous system, on immunity.

The second concerns products. The daily doses recommended by manufacturers, which the agency recorded at between 250 and 1,200mg, are comparable to those used in clinical trials where pharmacological activity is seen.

The third is the most severe. From the toxicity studies available, which were of poor quality, the experts could derive only an indicative, provisional toxicological value of 1.7 micrograms per kilo of body weight a day, or 0.1mg for a person weighing 60kg. That benchmark is probably exceeded by a large number of products, the agency writes, concluding that their safety in use cannot be guaranteed.

The fourth names the people who should steer clear: pregnant and breastfeeding women, people with diabetes, people with liver or heart conditions and, for want of data, children and teenagers.

The fifth is about medicines. ANSES identified interactions with around ten drugs, among them ciclosporin, tacrolimus, digoxin, metformin and two statins. It warns against taking berberine during any course of treatment, and alerts clinicians to the risk of undermining the effectiveness of certain medicines, cancer drugs in particular.

Dosage, a question with no official answer

We found no berberine dose endorsed by a health authority, in the UK or elsewhere in Europe.

Clinical trials have used 500 to 1,500mg a day, in patients under medical supervision. The labels ANSES surveyed ran from 250 to 1,200mg. Belgium, by contrast, had set a ceiling of 10mg of alkaloids a day, which the French agency considers to have no scientific basis. Between those figures the gap is more than a hundredfold: nobody knows how to define a dose that is both active and safe.

It is a decision to take with a GP or pharmacist, all the more so if you are on any medication.

Side effects and risks, the essentials

Digestive trouble leads the list of berberine side effects: diarrhoea, constipation, abdominal pain, nausea. ANSES also records a risk of low blood sugar and low blood pressure, and describes one case of a slowed heart rate six days into a course. Drug interactions remain the main risk for the general population, which is why anyone on prescribed medicines, whether for diabetes, the heart, cholesterol or a transplant, should ask before starting.

Because so little berberine is absorbed, some sellers have turned to skin patches. Nothing published shows that the compound gets through the skin in any useful amount, a point we return to in GLP-1 patches: do they work?.

From one country to the next, opposite rules

There is no common position in Europe. The 2019 opinion drew up the following picture, which may have changed since.

At the European Commission's request, the European Food Safety Authority (EFSA) is now assessing the safety of plant preparations containing berberine. Its scientific panel endorsed a draft opinion on 29 January 2026 and put it out to public consultation in the spring. The draft concludes that the available data do not allow a safe intake to be set for any of the thirteen plants examined, and notes signs of genotoxicity for berberine in laboratory tests. When this article was last updated, the final version had not been published. The Commission could then restrict or ban these plants in supplements across the EU.

In the UK, berberine is on open sale as a food supplement. The Committee on Toxicity, which advises the Food Standards Agency, had the EFSA draft on the agenda of its meeting on 31 March 2026, as a discussion paper that does not represent the committee's own view. We have found no UK decision since.

Capsules, patches, blends: a market ahead of the science

Alongside capsules of extract you will find patches, and formulas that pair berberine with other ingredients, blood orange extract most often, or fold it into products with "GLP-1" on the label. We have found no trial of these combinations. Our guide to GLP-1 supplements explains how to read such formulas.

What improves blood sugar and weight over the long run is found first in food, movement and sleep. Our piece on natural GLP-1 goes through it.

Frequently asked questions

What is berberine?

A yellow alkaloid extracted from the roots and bark of plants such as barberry and goldthread. It is sold in the UK as a food supplement, with no authorised health claim.

What are the proven benefits of berberine?

Trials run mainly in China, in people with diabetes, show a fall in blood glucose and blood fats. Food law in Great Britain and the EU does not recognise these effects as health claims.

Is berberine safe?

ANSES considers that its safety in use cannot be guaranteed, and a draft EFSA opinion in 2026 could not set a safe intake. The common side effects are digestive, and the main risk lies in interactions with medicines.

How much berberine should you take a day?

No health authority has endorsed a dose. ANSES finds pharmacological effects from 400mg a day, so the question is one for a GP or pharmacist.

Who should not take berberine?

ANSES advises against it for pregnant and breastfeeding women, children and teenagers, and people with diabetes or with liver or heart conditions. It also warns against using it alongside any medication.

Is berberine banned in the UK?

No. It is sold as a food supplement. Several European countries restrict the plants it comes from, the EFSA assessment could change the rules in the EU, and the UK's Committee on Toxicity has discussed that draft.

This article is for information only and is no substitute for advice from a healthcare professional. Never change your treatment without talking to your doctor.