What is Cranberry?

A number of related cranberries are found in areas ranging from damp bogs to mountain forests. These plants grow from Alaska to Tennessee as small, trailing evergreen shrubs. Their flowers vary from pink to purple and bloom from May to August depending on the species.


What is it used for?

The cranberry was primarily used as a traditional medicine for the treatment of bladder and kidney ailments among Native Americans. The berries were also used as a fabric and food dye, and as a poultice to treat wounds and blood poisoning. Sailors used the berries as a scurvy preventative. Despite a general lack of scientific evidence to indicate that cranberries or their juice are effective urinary acidifiers, interest persists among the public in the medicinal use of cranberries. Cranberries are used in eastern European cultures to reduce fever and, because of their folkloric role, in the treatment of cancers.

General uses

Some evidence exists for the use of cranberry in preventing, urinary tract infections. Other possible roles for cranberry with limited evidence include reduction of the risk of cardiovascular disease and cancer treatment.

What is the recommended dosage?

A lack of consistency in clinical trials makes dosage guidance difficult. Cranberry juice, juice concentrate, and dried extract have been studied in urinary tract infections. Doses of juice studied have ranged from 120 to 4000 mL/day; 400 mg of cranberry extract daily has been given in an effort to avoid the large volumes that seem to be required for efficacy.

How safe is it?


Those prone to kidney stones should contact their health care provider before taking a cranberry product.


Generally recognized as safe when used as food. Avoid dosages above those found in food because safety and efficacy are unproven.


In patients taking warfarin, drinking cranberry juice may increase the risk of severe bleeding, including hemorrhage. Because warfarin has a narrow therapeutic index, patients taking warfarin should limit or avoid concomitant ingestion of cranberry juice.

Side Effects

Extremely large doses can produce GI symptoms such as diarrhea.


There have been no reports of toxicity with the use of cranberry juice.


  1. Review of Natural Products. Facts & Comparisons 4.0. October 2008. Accessed October 14, 2008.
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