Under normal conditions, the body produces between 500 and 700 milliliters (about 16 to 24 ounces) of sweat, but if you are sweating profusely while sleeping, you could lose twice that [source: Exercise Physiology ].
Why do I sweat when I sleep?
Nobody likes to wake up in a pool of sweat in the middle of the night, and in order to figure out what might be causing night sweats, it's important to look at all of the possible variables. The first and most obvious thing to consider is temperature and overall comfort of the sleeping environment. Heat isn't the only environmental factor that might cause night sweating; humidity can also play a significant role. Other possible contributors to night sweats could include heavy blankets or pajamas, or general discomfort caused by an old mattress, a loud environment or even bedbugs.
The next thing to look at is your overall health. Has your diet changed? Have you been feeling fatigued? Flu symptoms include fever, which is a normal response to infection. Night sweats can result from a fever associated with a cold or flu symptoms for one or two nights, but beyond that, it could be something more serious.
One of the most common causes of night sweats is hot flashes associated with menopause, which result from hormonal changes in the body. A sudden drop in estrogen production can cause confusion for the hypothalamus (remember: It's the body's thermostat), causing a woman's skin temperature to increase by as much as 6 degrees, almost instantaneously [source: Breastcancer.org].
Most men reading this are probably counting their blessings that they don't suffer the discomfort of hot flashes, but not all men are exempt. Some men who are testosterone deficient, or who are taking testosterone-blocking drugs, can experience similar effects. For example, androgen deprivation drugs, which are often prescribed for prostate cancer, can disrupt the hypothalamus in 70 to 80 percent of men undergoing therapy. Most men are unlikely to admit that they're experiencing hot flashes, but androgen deprivation can lead to night sweats [source: Harvard Medical School].