Drug & supplement interaction

Kefir + Metformin

Metformin brand names: Glucophage, Metformin.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Kefir and Metformin in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Kefir and Metformin

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Metformin and Kefir in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Kefir safety at a glance

Kefir overall Generally safe Kefir is generally safe for most healthy people as a food.
Pregnancy Use caution Pasteurized-milk kefir is likely fine, but avoid unpasteurized or homemade versions and consult your doctor.
Breastfeeding Use caution Likely fine as a food, but choose pasteurized products and check with your doctor.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Metformin and Kefir? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Metformin

Interactions in our licensed database are recorded against drug classes, not just single drug names. Metformin is filed under 5 classifications — including organic cation transporter 2 (oct2) substrates, antidiabetes drugs, oral drugs. Kefir has documented interactions with 2 drug classes — the most serious being immunosuppressants (moderate) and disulfiram (antabuse) (minor) — and none of Metformin’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Kefir Does Interact With Other Medications

Kefir has 121 moderate, 1 minor known drug interactions in our database — Metformin isn’t one of them. If you take anything else, check it against the full list below.

Moderate 121 Minor 1 No known interaction 2,708 (incl. Metformin)
Taking anything else?

Check Another of Your Medications Against Kefir

Covers the 2,830 medications we’ve checked against Kefir. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Kefir and Metformin May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Bloating or gas / Diarrhea / Nausea Additional detail

    Kefir

    “Orally, kefir might cause bloating, nausea, intestinal cramping, diarrhea, and constipation with initial use. These symptoms are uncommon and usually resolve after continued use. However, severe bloating and abdominal cramping resulting in withdrawal from a clinical trial has been reported for 3 patients.”

    Kefir · Natural Medicines adverse-effect record, reported in constipation.

    4 sources cited
    1. 7636. St-Onge MP, Farnworth ER, Savard T, et al. Kefir consumption does not alter plasma lipid levels or cholesterol fractional synthesis rates relative to milk in hyperlipidemic men: a randomized controlled trial [ISRCTN10820810]. BMC Complement Altern Med 200 PubMed
    2. 95314. Turan I, Dedeli Ö, Bor S, Ilter T. Effects of a kefir supplement on symptoms, colonic transit, and bowel satisfaction score in patients with chronic constipation: a pilot study. Turk J Gastroenterol. 2014;25(6):650-6. PubMed
    3. 112046. Bellikci-Koyu E, Sarer-Yurekli BP, Karagozlu C, Aydin-Kose F, Ozgen AG, Buyuktuncer Z. Probiotic kefir consumption improves serum apolipoprotein A1 levels in metabolic syndrome patients: a randomized controlled clinical trial. Nutr Res 2022;102:59-70. PubMed
    4. 95311. Fathi Y, Faghih S, Zibaeenezhad MJ, Tabatabaei SH. Kefir drink leads to a similar weight loss, compared with milk, in a dairy-rich non-energy-restricted diet in overweight or obese premenopausal women: a randomized controlled trial. Eur J Nutr. 2016;55(1) PubMed

    Metformin

    Listed in the ADVERSE REACTIONS section of the FDA label for Metformin. Read the label on DailyMed ›

Reported for Kefir but not commonly for Metformin: stomach pain and constipation.

Effects for Metformin come from the ADVERSE REACTIONS section of its FDA label; effects for Kefir come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Overlapping uses

What Metformin Is Prescribed For, and What Kefir Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Metformin is a prescription medicine with approved uses on its FDA label. Kefir is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Metformin is prescribed for: Metformin is used to improve blood sugar (glucose) control in people with type 2 diabetes mellitus. It is always used together with diet and exercise, not instead of them. Metformin hydrochloride tablets and oral solution are approved for adults and children 10 years and older. Metformin hydrochloride extended-release tablets — including brands such as Fortamet, Glumetza, and Metformin Hydrochloride Extended Release — are approved for adults only.

Kefir has been studied for:

  • Diabetes studied, not established Kefir has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Kefir for diabetes

    It is unclear if oral kefir is beneficial in patients with diabetes.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Metformin on your own; if you are taking Kefir for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Kefir or Metformin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Kefir or Metformin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Metformin

This page covers Kefir only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metformin page lists 258 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Siberian Cocklebur (major), Acai (moderate), African Wild Potato (moderate) and Agaricus Mushroom (moderate).

By severity: 2 major · 217 moderate · 39 minor.

From our pharmacist’s overview on the Metformin page

“Siberian cocklebur is the ingredient I most want anyone taking metformin (Glucophage) to know about. It has caused severe low blood sugar in people, documented in humans, and it should not be combined with any glucose-lowering medication.”

Reviewed by 2 · Jul 18, 2026

Open the Metformin interaction page

One more smart check

Taking Kefir as Part of a Dietary Supplement Product? Check It for Interactions

We hold 29 real supplement products containing Kefir, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Kefir. Even though Kefir itself has no known interaction with Metformin, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Kefir and Metformin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Kefir
Steady interest

#1,064 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Metformin
Top 1%

#29 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Kefir reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Kefir and Metformin records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Kefir

What is Kefir?

  • Digestive health
  • Source of probiotics
  • Lactose intolerance support
  • General immune support
  • Gut microbiome balance

Kefir is a fermented drink made by adding kefir grains to milk (or sugar water), creating a tangy beverage rich in probiotics. It is generally a safe, nutritious food that may support gut health, but strong evidence for treating specific medical conditions is still limited. If you have a weakened immune system or other health concerns, check with your pharmacist or doctor first.

Fermented milk or water with kefir grains (a culture of bacteria and yeast) · Drinkable fermented milk, water kefir, powdered or capsule probiotic products

An interaction check asks whether these two react with each other — it does not ask whether Kefir is a good idea for someone in your situation. Here is what our Kefir record says about it on its own.

Kefir: dosing

There is no official standardized dose for kefir because it is a food, not a regulated medicine. Many people drink anywhere from a few ounces to a cup per day, often starting small and increasing gradually to allow the gut to adjust.If you use a powdered or capsule probiotic product, follow the directions on the label.

From our Kefir monograph — the full record covers uses, side effects and every documented interaction.

Read the full Kefir monograph & all interactions
Medication

About Metformin

What Is Metformin Used For?

Brand names: Glucophage, Metformin

Metformin is used to improve blood sugar (glucose) control in people with type 2 diabetes mellitus. It is always used together with diet and exercise, not instead of them.

Metformin hydrochloride tablets and oral solution are approved for adults and children 10 years and older. Metformin hydrochloride extended-release tablets — including brands such as Fortamet, Glumetza, and Metformin Hydrochloride Extended Release — are approved for adults only.

See full Metformin drug information
Keep checking

Other Drugs & Kefir

Browse every other medication we’ve checked against Kefir — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
121Moderate
1Minor
2,707No known interaction
121 Moderate 1 Minor 2,707 No interaction
Moderate

121 interactions

Showing 60 of 121 moderate interactions — see all 121 on the Kefir page.

Minor

1 interaction

No interaction 2,707 drugs checked — show the list

We also checked Kefir against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,707 medications checked with no known interaction — see the full Kefir list.

See the full Kefir interactions page
See every supplement checked against Metformin, ranked by severity
Evidence & sources

Kefir References

The 10 references that drive our Kefir monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. St-Onge MP, Farnworth ER, Savard T, et al. Kefir consumption does not alter plasma lipid levels or cholesterol fractional synthesis rates relative to milk in hyperlipidemic men: a randomized controlled trial [ISRCTN10820810]. BMC Complement Altern Med 200 PubMed
  2. Murofushi M, Mizuguchi J, Aibara K, Matuhasi T. Immunopotentiative effect of polysaccharide from kefir grain, KGF-C, administered orally in mice. Immunopharmacology 1986;12:29-35. PubMed
  3. Shiomi M, Sasaki K, Murofushi M, Aibara K. Antitumor activity in mice of orally administered polysaccharide from Kefir grain. Jpn J Med Sci Biol 1982;35:75-80. PubMed
  4. Rimada PS, Abraham AG. Polysaccharide production by kefir grains during whey fermentation. J Dairy Res 2001;68:653-61. PubMed
  5. De Vrese M, Keller B, Barth CA. Enhancement of intestinal hydrolysis of lactose by microbial beta-galactosidase (EC 3.2.1.23) of kefir. Br J Nutr 1992;67:67-75.
  6. Athanasiadis, I., Boskou, D., Kanellaki, M., and Koutinas, A. A. Low-temperature alcoholic fermentation by delignified cellulosic material supported cells of kefir yeast. J.Agric.Food Chem. 1999;47(10):4474-4477. PubMed
  7. Rabl, W., Liniger, B., Sutter, K., and Sigrist, T. [Ethanol content of Kefir water]. Blutalkohol 1994;31(2):76-79.
  8. Fathi Y, Faghih S, Zibaeenezhad MJ, Tabatabaei SH. Kefir drink leads to a similar weight loss, compared with milk, in a dairy-rich non-energy-restricted diet in overweight or obese premenopausal women: a randomized controlled trial. Eur J Nutr. 2016;55(1) PubMed
  9. Turan I, Dedeli Ö, Bor S, Ilter T. Effects of a kefir supplement on symptoms, colonic transit, and bowel satisfaction score in patients with chronic constipation: a pilot study. Turk J Gastroenterol. 2014;25(6):650-6. PubMed
  10. Bellikci-Koyu E, Sarer-Yurekli BP, Karagozlu C, Aydin-Kose F, Ozgen AG, Buyuktuncer Z. Probiotic kefir consumption improves serum apolipoprotein A1 levels in metabolic syndrome patients: a randomized controlled clinical trial. Nutr Res 2022;102:59-70. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Kefir and Metformin Together: Common Questions

Is it safe to take Kefir with Metformin?
We do not list a known interaction between Kefir and Metformin. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Kefir and Metformin have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Kefir and Metformin used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Kefir in each. That is a conversation for your prescriber, especially if Metformin is being adjusted to a target.
How was the Kefir and Metformin combination checked?
Interactions in our licensed database are recorded against drug classes. Metformin is filed under 5 classifications, and Kefir has documented interactions with 2 drug classes — none of Metformin's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Kefir interact with any other medications?
Yes. Kefir has 122 documented drug interactions in our database — Metformin is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Metformin interact with any supplements?
Yes. Metformin has documented interactions with 258 supplements in our database — Kefir is not one of them. The Metformin interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

Kefir monograph Uses, safety profile, and every drug interaction in one place Metformin drug information The full plain-English guide to this medication Metformin supplement interactions Every supplement checked against Metformin, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 10 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Metformin and Kefir?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.