Summary
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Does cranberry help treat or prevent UTIs?
Drinking cranberry juice or taking a cranberry supplement may help reduce the risk of recurrent UTIs in women, although the evidence is limited. Drinking the juice is more likely to help than taking a supplement. Drinking the juice is more likely to help than taking a supplement. More limited evidence suggests cranberry may also reduce symptoms of overactive bladder, lower urinary tract symptoms (LUTS) and symptoms of prostatitis. See What It Does for details.
There is less evidence of benefit for dried cranberries and cranberry chews, and the benefit of cranberry for UTIs in children remains uncertain.
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What is in cranberry that helps it work against UTIs?
Cranberries contain a variety of polyphenolic compounds that include proanthocyanidins (PACs). PACs have been shown to limit the ability of E. coli bacteria to adhere to the walls of the bladder and urinary tract. By limiting this adhesion, PACs from cranberry — particularly water-soluble A-type PACS (at 36 mg once or twice per day) — may reduce the risk of urinary tract infections (UTIs). See What It Is for more information. 
Best cranberry juice or pills?
ConsumerLab's tests determined the amounts of water-soluble PACs in cranberry products. Amounts per serving ranged nearly 200-fold, from as little as just 0.54 mg to as much as 105.6 mg, and the cost to get 36 mg of PACs ranged from just 35 cents to $21.67. See What CL Found for details.
Our Top Picks among cranberry juices and supplements each provided the highest amount of PACs among competing brands and did so at much lower cost. This means that you can avoid as many as 153 Calories and get an effective dose of PACs for preventing UTIs by drinking, for example, our Top Pick pure cranberry juice as opposed to a much larger amount of a sweetened cranberry cocktail (see What to Consider When Buying).
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What to look for on cranberry labels?
When looking at the amounts of PACs listed on labels, it is critical that you also look for the type of PACs (such as A-type PACs versus OSP-PACs), as the units are very different (see PAC Test Methods for details). If the type of PAC is not disclosed, the amount is meaningless.
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Is cranberry safe to use?
Cranberry beverages or dietary supplements are generally safe for most people, although people with diabetes, those at risk for kidney stones, and those with an aspirin allergy may need to use caution. See Concerns and Cautions for details.
