Reviewed on 6/11/2021
Other Name(s):

Fermented Dairy Product, Fermented Milk, Fromage Kéfir, Kéfir, Kefir Cheese, Kefir Grains, Kefir Yogurt, Lait Fermenté, Produit Laitier Fermenté.


Kefir is a product made by fermenting milk.

People use kefir for poor digestion, upset stomach, lactose intolerance, diarrhea following treatment with antibiotics, and high cholesterol.

How does it work?

Kefir contains actively growing bacteria and yeast. Their effect on milk results in production of enzymes and chemicals that affect the way food is digested.


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Uses & Effectiveness

Likely Ineffective for...

  • Lowering serum cholesterol. Research shows that taking kefir has little or no effect on cholesterol levels.

Insufficient Evidence to Rate Effectiveness for...

  • Diarrhea associated with taking antibiotics. Some research shows that a specific kefir-containing drink (Probugs, Lifeway Foods, Inc.) does not reduce diarrhea in children caused by antibiotics.
  • Soreness and swelling inside the mouth, caused by chemotherapy (oral mucositis). Early research shows that rinsing the mouth with kefir and swallowing 250 mL of kefir twice daily for the first 5 days of chemotherapy does not prevent the development of sores inside the mouth caused by chemotherapy.
  • Lactose intolerance.
  • Improving digestion.
  • Other conditions.
More evidence is needed to rate the effectiveness of kefir for these uses.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).

Side Effects

Kefir is POSSIBLY SAFE for most adults when taken by mouth for up to 6 months.

Kefir can cause intestinal cramping and constipation, especially when use is started.


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Special Precautions & Warnings

Children: Kefir is POSSIBLY SAFE for children between the ages of 1 and 5 years when taken by mouth for up to 10 days.

Pregnancy and breast-feeding: There is not enough reliable information about the safety of taking kefir if you are pregnant or breast-feeding. Stay on the safe side and avoid use.

AIDS and other conditions that weaken the immune system: Kefir contains actively growing bacteria and yeast. There is some concern that people with a weakened immune system might be more likely to develop infections from these bacteria or yeast.


Medications that decrease the immune system (Immunosuppressants)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Kefir contains live bacteria and yeast. The immune system usually controls bacteria and yeast in the body to prevent infections. Medications that decrease the immune system can increase your chances of getting sick from bacteria and yeast. Taking kefir along with medications that decrease the immune system might increase the chances of getting sick.

Some medications that decrease the immune system include azathioprine (Imuran), basiliximab (Simulect), cyclosporine (Neoral, Sandimmune), daclizumab (Zenapax), muromonab-CD3 (OKT3, Orthoclone OKT3), mycophenolate (CellCept), tacrolimus (FK506, Prograf), sirolimus (Rapamune), prednisone (Deltasone, Orasone), corticosteroids (glucocorticoids), and others.

Disulfiram (Antabuse)Interaction Rating: Minor Be cautious with this combination.Talk with your health provider.

Kefir might contain alcohol. The body breaks down alcohol to get rid of it. Disulfiram (Antabuse) decreases the break-down of alcohol. Taking kefir along with disulfiram (Antabuse) can cause a pounding headache, vomiting, flushing, and other unpleasant reactions. Don't drink any alcohol if you are taking disulfiram (Antabuse).


The appropriate dose of kefir depends on several factors such as the user's age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for kefir. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

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