For years, people have used cranberry juice to prevent and help cure urinary tract infections (UTIs). There is limited proof that this is worth trying.
Pure cranberry juice, cranberry extract, or cranberry supplements may help prevent repeated UTIs in women, but the benefit is small. It helps about as much as taking antibiotics to prevent another UTI.1 Using cranberry products to prevent UTIs may be expensive, and some women complain of the taste. No single concentration of cranberry juice, extract, or supplement has been studied, so it's hard to know which product to choose.
If you do want to try cranberry juice to prevent UTIs, it's better to drink pure, unsweetened cranberry juice (rather than cranberry juice cocktail). Drinking cranberry juice cocktail doesn't seem to prevent UTIs better than drinking any other fruit juice.2
There is no proof that cranberry can cure a UTI. Cranberry is not well tested as a UTI treatment.
Cranberries may affect how warfarin works, which can be dangerous. If you are taking the anticoagulant medicine warfarin (such as Coumadin), talk to your doctor before using cranberry to prevent a UTI.