Probiotics

Kefir

Also called: kefir grains

A fermented milk drink with many microbes.

Why people take it
Gut health.
What the evidence says
A healthy food; little disease evidence.
How it is usually taken
About one cup a day as a fermented drink.
Be careful
Contains milk.
Medicines it can interact with
No important medicine interactions are known, but tell your doctor and pharmacist about every supplement you take.

Other probiotics

Common questions

What is Kefir?

A fermented milk drink with many microbes.

Why do people take Kefir?

Gut health.

Does Kefir work?

A healthy food; little disease evidence.

How much Kefir do people take?

About one cup a day as a fermented drink.

Is Kefir safe?

Contains milk.

Does Kefir interact with medicines?

No important medicine interactions are known, but tell your doctor and pharmacist about every supplement you take.

Sources and further reading

Last reviewed 31 October 2026. Written by Satya Babu.

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For information only, not medical advice. Supplements are not medicines: they are not tested and approved like drugs before they are sold, and they can interact with medicines. Talk to your doctor or pharmacist before you start one, especially if you are pregnant or breastfeeding, take regular medicines, or have kidney, liver or heart disease.