What Happens to Your Body When You Don’t Sleep for Days?

While occasional lack of sleep may not seem like a big deal, its impact can be intense and its effects can linger. And if you make it a habit, not sleeping enough can have severe consequences for your health.

“As a society, as families and as individuals, we have not yet fully appreciated the importance of sleep,” says Terry Cralle, RN, a certified clinical sleep educator based in Fairfax, Virginia. “Sleep, along with diet and exercise, constitutes the very foundation of good health.” These health factors so interconnected that each of them needs to be a priority, she adds.

After 24 hours of no sleep, stress hormones cortisol and adrenaline increase to compensate for the fatigue you’re battling and help you function, says John Cline, PhD, a licensed clinical psychologist and fellow of the American Academy of Sleep Medicine.

“The brain is trying to cope with not having its opportunity to rejuvenate itself, so we have these heightened stress hormones to keep the body activated,” says Dr. Cline.

“Judgment is affected, memory is impaired, and there’s deterioration in decision-making ability and eye-hand coordination,” says Cralle. You also tend to be more emotionally reactive, attention is decreased, hearing is impaired, and there’s an increase in your risk of death from a fatal accident, she says.

At this point, high levels of inflammatory markers in the bloodstream are common, which can eventually lead to cardiovascular disease and high blood pressure, says Cralle.

Additionally, this level of sleep deprivation affects hormone balance, which can result in emotional dysregulation. As your body keeps pumping cortisol into your bloodstream, raising your heart rate and blood pressure to keep you alert, the additional stress can increase feelings of anxiety and mood swings, says Cline.

If you were cranky, on edge, and zombie-like before, those symptoms will likely worsen after 36 hours with no sleep, says Cline. “Everything going on at 24 hours is going to be worse at 36 hours,” he says.

Cognitive impairment grows more severe as well. You’re likely to feel sluggish and experience delayed reaction times, foggy memory, and an inability to concentrate, learn new information, and process social cues, says Michelle Drerup, PsyD, a psychologist and the director of the behavioral sleep medicine program at Cleveland Clinic.

At the 48-hour mark, you’re dealing with “extreme sleep deprivation,” says Dr. Drerup.

After two days of no sleep, you can count on increased irritability, anxiety, foggy memory, and impaired thinking, says Hussam Al-Sharif, MD, a pulmonologist and sleep medicine specialist at Mayo Clinic in Eau Claire, Wisconsin.

Some people may even experience hallucinations, seeing or hearing things that aren’t really there. “Some people feel depressed, and some might become euphoric,” says Dr. Al-Sharif.

Expect significant deficits in concentration, motivation, perception, and other higher mental processes after so many sleepless hours, says Cralle.

You’re going to feel pretty miserable and dysfunctional with this much sleep deprivation, adds Cline. “The brain is fighting against wanting to shut down, and that’s going to create a really fragile emotional state,” he says.

Microsleeps also increase in length and frequency at this level of sleep deprivation, which Cline describes as a protective response by the body. But those fleeting moments of involuntary rest are incredibly risky, especially if you’re behind the wheel, operating heavy equipment, or responsible for make-or-break decisions at work.

This point of sleep deprivation is also when the mind is ripe for hallucinations, delusions, and paranoia, says Al-Sharif.

• The mental and physical effects of going without sleep for 24 hours include elevated cortisol levels, impaired coordination, and poor memory and judgment.
• Not sleeping for 48 hours is considered extreme sleep deprivation, and the body copes by shutting down for involuntary episodes of sleep called microsleeps that can be dangerous should they occur at the wrong time.
• A lack of sleep for 72 hours often results in significant deficits in concentration, motivation, and perception, as well as potential hallucinations, delusions, and paranoia.
• It’s recommended that adults get between seven and nine hours of sleep each night and stick to a consistent sleep schedule to reap the many health benefits of high-quality sleep.