Bleeding DisordersCranberry

Should you avoid drinking cranberry juice while taking warfarin?

A review published in the journal Pharmacotherapy warns that drinking large amounts of cranberry juice while taking the blood thinner, warfarin (Coumadin) might increase the risk of bleeding.

How much cranberry juice do you have to drink?

That’s not clear.

The interaction has been reported about a dozen times, but the actual amount each patient drank each day is often not known for sure. Sometimes it’s not even clear if there actually was an interaction.

  • In one case a patient drank 2 liters (2 quarts) of cranberry juice every day for 2 weeks to prevent a recurrent urinary tract infection.
  • In another case the patient started drinking 24 ounces/day (about 3 large glassfuls) of cranberry juice as a source of vitamin C.

The bottom line?
The authors state, “In patients taking warfarin, an interaction may occur if they increase their intake of cranberry juice or occasionally ingest a large volume; however, small amounts of the juice are not expected to cause such an interaction.”

If your doctor prescribes warfarin, be sure you disclose your use of cranberry juice.

2/20/07 19:16 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.