Night sweats are surprisingly common, and in most cases, they have a straightforward explanation. About 41% of adults report experiencing night sweats within the past month, so if your boyfriend is waking up damp or soaking through the sheets, he’s far from alone. The causes range from a too-warm bedroom to underlying health conditions, and figuring out which one applies usually starts with ruling out the simplest explanations first.
The Bedroom Itself May Be the Problem
Before looking at medical causes, it’s worth checking the sleeping environment. The ideal bedroom temperature for quality sleep is between 60 and 67°F (15 to 19°C), which is cooler than most people keep their homes. A room that feels comfortable while you’re awake and moving around can easily be too warm for sleep, when your body is trying to lower its core temperature as part of its natural sleep cycle.
Heavy blankets, memory foam mattresses (which trap heat), and synthetic sleepwear all compound the problem. Men also tend to run warmer than women during sleep due to higher muscle mass and metabolic rate. If you’re comfortable under the covers but he’s sweating, the difference in your body temperatures may be all it takes. Switching to breathable bedding and lowering the thermostat is the easiest first step.
Food, Alcohol, and Caffeine Before Bed
What your boyfriend eats and drinks in the evening can directly trigger sweating at night. Spicy foods, alcohol, and caffeine all raise core body temperature or stimulate sweat glands. Alcohol is a particularly common culprit because it causes blood vessels to widen (vasodilation), which sends a rush of warmth to the skin and triggers sweating as the body tries to cool down. If the sweating tends to happen on nights when he’s had a few drinks or a late, heavy meal, the pattern is likely diet-related.
Stress, Anxiety, and the Nervous System
The brain controls sweating through two separate pathways: one for temperature regulation and one for emotions. Stress and anxiety activate the sympathetic nervous system, which is the body’s “fight or flight” response, and that system can trigger sweat glands even when there’s no actual overheating happening. This is the same mechanism behind sweaty palms during a stressful moment, except during sleep it can affect the whole body.
Stress hormones like noradrenaline directly activate sweat glands during emotional arousal. If your boyfriend is going through a high-pressure period at work, dealing with financial stress, or experiencing anxiety that carries into sleep, his nervous system may be staying in an alert state overnight. People with anxiety disorders or PTSD are particularly prone to this kind of sweating, but even everyday stress can be enough.
Sleep Apnea Is a Major Overlooked Cause
Obstructive sleep apnea, a condition where breathing repeatedly stops and restarts during sleep, is one of the most underdiagnosed causes of night sweats in men. About 31% of men with sleep apnea experience frequent night sweats (three or more times per week), compared to just 9% of men in the general population. That makes someone with sleep apnea roughly three times more likely to sweat at night.
The connection makes sense: when the airway closes and oxygen drops, the body enters a stress response. Heart rate spikes, blood pressure rises, and the sympathetic nervous system fires up, all of which produce sweating. If your boyfriend snores heavily, gasps during sleep, or feels exhausted during the day despite getting enough hours in bed, sleep apnea is worth investigating. It’s diagnosed through a sleep study, which can now often be done at home with a portable monitor.
Low Testosterone and Hormonal Shifts
Testosterone levels in men decline gradually starting around age 30, and low testosterone is a recognized cause of night sweats. The mechanism is similar to hot flashes in menopause: when sex hormone levels drop, the brain’s thermostat (the hypothalamus) becomes more sensitive to small changes in body temperature, triggering sweating episodes as an overcorrection.
Low testosterone can also come with other symptoms like fatigue, reduced sex drive, mood changes, and difficulty concentrating. Because low testosterone itself can be a sign of other issues, including pituitary gland problems, kidney disease, or liver disease, a diagnosis usually leads to additional blood work to rule out deeper causes.
Medications That Trigger Sweating
Several common medications list night sweats as a side effect. The most frequent offenders include antidepressants (especially SSRIs and SNRIs), hormone therapy, diabetes medications that lower blood sugar, and methadone. If your boyfriend recently started or changed a medication and the sweating began around the same time, the connection is likely not a coincidence. This is worth bringing up with his prescriber, as adjusting the dose or switching to a different option can sometimes resolve it.
Less Common but Serious Causes
In a small number of cases, persistent night sweats point to something more serious. Infections, including tuberculosis and HIV, can cause drenching sweats at night. Certain cancers, particularly lymphoma and leukemia, are associated with night sweats, often alongside unexplained weight loss, fevers, and fatigue. Acid reflux (GERD) has also been linked to night sweats in some patients, which makes sense given that lying down worsens reflux and the discomfort can activate the body’s stress response. Hypoglycemia, or low blood sugar episodes during the night, is another possibility, especially in someone with diabetes.
The sweating that warrants medical attention typically has certain characteristics. It’s drenching rather than mild dampness, happening regularly rather than occasionally, and showing up alongside other symptoms like unexplained weight loss, persistent fevers, swollen lymph nodes, or significant fatigue. A single sweaty night after too many blankets is not the same as weeks of soaking through shirts.
How to Narrow Down the Cause
Tracking patterns is the most useful thing you can do before seeking medical advice. Pay attention to whether the sweating correlates with alcohol, stress, specific meals, or certain nights of the week. Notice whether it happens all over his body or mainly on his head, chest, and back (which is more typical of hormonal and medical causes). Check whether the room temperature is above 67°F and whether his bedding traps heat.
If the sweating is new, severe, happening multiple nights per week, or accompanied by other symptoms like weight changes, daytime fatigue, or snoring, those are signals that something beyond the environment is at play. A doctor can run blood work to check hormone levels, blood sugar, and markers of infection or inflammation, and can refer for a sleep study if apnea is suspected. In many cases, identifying and addressing the underlying cause resolves the sweating entirely.