Cranberry juice, cranberry extract and cranberry pills do not treat a bladder infection you already have. That is the word from the National Institute of Diabetes and Digestive and Kidney Diseases, part of the National Institutes of Health.

The institute says researchers do not think your diet can prevent or treat bladder infections. Some research suggests cranberry products may help prevent an infection, the institute notes, but there is not enough evidence to be sure.

The institute does point to one habit that helps. Drinking enough liquids keeps you hydrated and can help prevent or relieve bladder infections, it says. Water is best.

For safety reasons, the institute advises talking with your health care professional before using dietary supplements such as vitamins, or any complementary or alternative medicine or practice. If you think you have a bladder infection, talk to your doctor about treatment.

The institute's guidance on eating, diet and nutrition for bladder infections in adults was last reviewed in April 2024.