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What is it? Overview Usage Side Effects and Warnings

Cranberry Side Effects and Warnings

Written by FoundHealth.

Safety Issues

As a widely eaten food, cranberry is thought to have a generally good safety profile.

However, several case reports suggest that cranberry could interact with the drug warfarin (Coumadin), potentially leading to internal bleeding. 1 Two formal studies have failed to find evidence of such an interaction, 2 while a third study did find that cranberry can increase the blood thinning effect of warfarin in healthy male subjects. 3 Prudence would suggest caution, especially when consuming more than eight ounces of cranberry juice daily.

In addition, cranberry juice might allow the kidneys to excrete weakly alkaline drugs more rapidly, thereby reducing their effectiveness. This would include many antidepressants and prescription painkillers.

Finally, indirect evidence suggests that regular use of cranberry concentrate tablets might increase risk of kidney stones . 4

Interactions You Should Know About

If you are taking:

  • Warfarin (Coumadin) : Use of cranberry might lead to excessive bleeding.
  • Weakly alkaline drugs (including many antidepressants and prescription painkillers): Cranberry might decrease their effectiveness.


  1. Committee on Safety of Medicines. Possible interaction between warfarin and cranberry juice. Current Problems in Pharmacovigilance. 2003;29:8.
  2. Li Z, Seeram NP, Carpenter CL, et al. Cranberry does not affect prothrombin time in male subjects on warfarin. J Am Diet Assoc. 2006;106:2057-2061.
  3. Mohammed Abdul MI, Jiang X, Williams KM, et al. Pharmacodynamic interaction of warfarin with cranberry but not with garlic in healthy subjects. Br J Pharmacol. 2008 Jun 2.
  4. Terris MK, Issa MM, Tacker JR. Dietary supplementation with cranberry concentrate tablets may increase the risk of nephrolithiasis. Urology. 57(1):26-9.


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