Urinary tract infections affect 3 million Americans each year. If you’ve ever experienced one, someone probably told you to drink a big glass of cranberry juice.

But contrary to popular belief, the cranberry juice at the grocery store may not do much to treat this infection. A urologist at the Texas A&M University College of Medicine explains that store-bought juice can effectively hydrate your body, which is always a good thing. But the juice doesn’t contain enough of the cranberry’s active ingredient that helps treat infections.

The cranberry’s active ingredient helps stop bacteria from sticking to the bladder wall, which is what happens during a urinary tract infection. So the cranberry’s ingredient, in high enough concentrations, helps prevent the bacteria’s ability to cause an infection.

But, there is still hope for preventing this pesky problem. A study published in the American Journal of Obstetrics and Gynecology found that cranberry capsules — 16 ounces of cranberry juice in one pill — lowered the risk of urinary tract infections by 50 percent among women who had a catheter in place. Boone said the capsules are more effective because they contain a potent amount of the cranberry’s active ingredient.

So if you feel the signs of a urinary tract infection, be sure to see your doctor to get a proper diagnosis. The symptoms include frequent, painful urination and pelvic pain.

If an infection is the culprit, consider asking a pharmacist for cranberry capsules. While a urinary tract infection can usually be treated with antibiotics, it shouldn’t be taken lightly. If left untreated, it can evolve into a serious kidney infection.