Virginians love their sweet tea year-round. Unfortunately, new research suggests drinking a lot of iced tea during the summer could cause kidney stones—especially if you’re already at risk.

How? Dehydration from not drinking enough fluids is the most common cause of kidney stones. During the summer, when many people are already dehydrated from sweating, they choose iced tea to quench their thirst and rehydrate their bodies. This could be a double-whammy for people who have the tendency to form the most common type of kidney stones, which are calcium-oxalate stones. Iced tea contains high concentrations of oxalate, an acid that naturally occurs in plants, and a key chemical that leads to kidney stone formation.

So, adding a spike in iced tea consumption to an already-dehydrated body, and you raise your risk of kidney stones.

It’s worth noting that hot tea also contains oxalate, though people generally do not drink as much hot tea as iced tea. Other foods with high concentrations of oxalates include chocolate, spinach, rhubarb, beets, and peanuts.

About 3 million people are treated for kidney stones in the U.S. each year—about half a million in emergency rooms. And men are more likely to suffer from painful kidney stones than women. As always, if you have questions about kidney stones, or your risks for kidney stones, check with your doctor.