THERE’S NO WAY around it: If you’re athletic, you need to know how to keep your body hydrated and recognize signs of trouble. With hot, sweaty weather on its way, we asked a renowned Cornell urologist to give us his best advice on an often overlooked topic. Here, his seven top tips.

1. Know that you’re usually dehydrated

Under hydration is a huge problem, especially if you train intensely. Many studies have shown that before a game, even elite athletes can be under hydrated.

2. Drink every 15 minutes while working out

Good hydration means drinking about two liters—a day. Even if you don’t sweat a lot, if you do intense training you should drink an additional 100ml of water every 15 minutes of your workout.

3. Determine what your pee is telling you

Your urine should always be pale yellow. If during or after a workout you’re not peeing a lot—young guys urinate about six times a day on average, usually every three to four hours—or your pee is dark yellow, you’re not properly hydrated.

4. Extra protein is OK if you’re hydrated

I’m not against supplementing with protein, but guys who are athletic should know that excess protein can put a significant load on their kidneys if they’re dehydrated.

If you’re an active athlete and not keeping adequately hydrated, eating more than the recom-mended 1 gram per pound of body weight daily can increase your risk for kidney problems. But consuming protein after an intense workout can aid muscle recovery. Bottom line: Protein supplements are fine, just make sure you’re very well hydrated when you take them.

5. Know your kidney numbers

Young guys should get a general physical checkup at least every other year, if not annually, for routine blood tests that look at kidney function. If the kidneys are normal, it’s very hard to damage them. But if a kidney isn’t working perfectly—and many kidney diseases are symptomless—you can put additional stress on the organ. So I recommend getting a checkup before upping your protein intake, especially if you’re doing it for a big athletic contest, like a triathlon. Typical symptoms of bad kidney function are swelling, fatigue, and upset stomach or digestion issues. If your urine turns foamy or dark brown or red, call your doctor.

6. Don’t worry about kidney stones until later in life

Stones are rare in young adults, but can form from dehydration, too much animal protein, a salty diet, or diuretic abuse. Young guys have some natural buffers. That changes once you pass 40. The average 25- or 30-year-old doesn’t need to see a urologist unless his numbers are off or his physician spots something.

7. Opt for plain water over sports drinks

Sports drinks are fine for replacing amino acids and electrolytes after an intense six-hour bike ride or a multihour run. But even then, one drink is more than enough. Plus, it’s rare to need a lot of extra salt unless you’re doing a marathon or something similar.

Water should still be your main therapy, so make sure most of your fluids come from water—not coffee, not tea/iced tea, not fruit juices. Otherwise you’re setting yourself up for a stone.

by Bejamin Choi, M.D