How much you should sweat during a workout

Apr 6, 2015 at 7:30 p.m. ET
Image: Pure Body/Getty Images

You're partway through an intense workout at the gym and you're sweating... a lot. That must mean you're burning plenty of calories and all that exercise is paying off, right? Or, is there such a thing as sweating too much when you're exercising?

The truth is that how much you sweat isn't an indication of how many calories you're burning, and sweating too much can signal something is wrong. But, it varies from person to person.

"Everyone sweats differently," says Dr. Rob Truax, a family and sports medicine specialist at University Hospitals Case Medical Center. "It’s all dependent on one’s genetic makeup and how the body responds to body temperature."

In general, how much you sweat isn't a sign of a more serious condition. Some people just sweat more than others. That said, there are times when excessive sweating can be a red flag that your body has gotten overheated.

"The bigger concern is this: Is sweating too much actually indicative of you being in too warm of an environment that could be dangerous?" says Truax. For example, "If you’re sweating a lot and it’s 90 degrees out, that’s dangerous."

Hence, the importance of drinking enough fluids before you exercise.

Truax says a good way to measure whether you're well-hydrated before a workout is to weigh yourself before and after you exercise for one hour. The amount of weight you've lost is your "sweat weight," he explains. It's normal to lose between 1 and 2 percent of your total body weight during one workout session.

"If you lose too much weight — more than 2 percent — you're dehydrated and it can impact your performance and potentially your health," he says. "However, if you gain weight, you've actually drunk too much. You can overhydrate yourself too."

So, what can happen if you overheat while you exercise, either from working out in an environment that's too hot or being too warmly dressed? Dehydration, heat exhaustion and heat stroke are among the risks.

Symptoms of dehydration can include deep or dark yellow urine, extreme thirst, dizziness, weakness, dry mouth, swollen tongue, heart palpitations, an inability to sweat and fainting. Nausea, vomiting, muscle cramps, excessive thirst, dizziness, headaches, weakness, fatigue, confusion, profuse sweating and loss of consciousness are all signs of heat exhaustion.

Heat stroke, which is much more serious and constitutes a medical emergency, can often progress from heat exhaustion and comes with some of the same symptoms, like nausea and vomiting, extreme dizziness or light-headedness, disorientation or confusion, lack of sweat despite extreme heat, loss of consciousness, muscle cramps, throbbing headache, rapid heartbeat, rapid and shallow breathing, red and hot dry skin, and even seizures, among others.

So, what's the takeaway? Drink enough fluids before you work out so you don't get dehydrated, and make sure you're not exercising in excessively high temperatures. If you take those precautions, how much you sweat doesn't matter.

"Sweating is a natural, normal process that we have absolutely no control over," says Truax.

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