Skip to Content

Can you pass out from lack of sleep?

Not getting enough sleep can definitely take a toll on your body and make you feel exhausted. But can lack of sleep actually cause you to lose consciousness and pass out? Let’s take a closer look at whether not getting enough Zzz’s can lead to fainting.

What happens when you don’t get enough sleep?

Sleep is essential for allowing your body and brain to recharge. When you don’t get adequate sleep, it can lead to a number of effects including:

  • Fatigue and sleepiness during the day
  • Difficulty concentrating and focusing
  • Impaired memory and cognitive function
  • Mood changes like irritability, anxiety, and depression
  • Weakened immune system
  • Increased risk of illness and disease
  • Slower reaction time and increased risk of accidents

Overall, lack of sleep stresses your body and impairs your ability to function normally. But could it actually make you faint?

Can lack of sleep lead to fainting?

Fainting, also called syncope, is a brief loss of consciousness caused by a temporary drop in blood flow to the brain. There are several potential causes of fainting including:

  • Orthostatic hypotension – A sudden drop in blood pressure when standing up. This is common cause of fainting.
  • Dehydration – Low fluid levels can lead to blood pressure drops.
  • Low blood sugar – Particularly in people with diabetes.
  • Heart arrhythmias – Abnormal heart rhythms.
  • Hyperventilation – Overbreathing causes low carbon dioxide and oxygen levels.
  • Seizures – Epileptic seizures can mimic fainting.
  • Psychological causes like severe anxiety or phobias.

So where does lack of sleep fit in? Here’s what the research shows about the connection between sleep deprivation and fainting risk:

Poor sleep can lower blood pressure

Not getting enough sleep affects hormones that regulate blood pressure like endothelin and vasopressin. Blood pressure normally drops at night during sleep and rises upon waking. With sleep deprivation, this normal fluctuation can become impaired leading to drops in daytime blood pressure.

A study published in the journal Hypertension found that getting just 5 hours of sleep in a 24-hour period caused daytime blood pressure to be lower compared to getting a full 8 hours of sleep.

Sleep loss is linked with orthostatic hypotension

As mentioned, orthostatic hypotension is one of the most common reasons people faint. It happens when blood pressure drops rapidly when you stand up, reducing blood flow to the brain. Research shows that lack of sleep increases the risk of orthostatic hypotension and excessive drops in blood pressure upon standing.

For example, a study in the Journal of Applied Physiology had participants sleep just 5 hours per night for 5 nights. After the sleep restriction period, they had greater drops in blood pressure when moving from lying down to standing upright compared to after getting 8.5 hours of sleep per night.

Dehydration risk may increase

Getting inadequate sleep can make you more prone to dehydration by affecting hydration hormones. With severe dehydration, fainting can occur due to low fluid and electrolyte levels in the body. Even mild dehydration from restricted sleep could potentially contribute to periods of lightheadedness or dizziness.

Blood sugar control suffers

Not getting enough sleep can also impact blood sugar levels and insulin sensitivity. For people with diabetes prone to low blood sugar episodes, lack of sleep could raise the risk of fainting spells related to severe hypoglycemia.

How much sleep deprivation causes fainting?

There’s no specific amount of sleep deprivation that will automatically cause fainting. The effects really depend on the individual. However, research gives us a general idea of how lack of sleep impacts fainting risk:

  • Getting less than 6 hours of sleep per night over multiple nights can begin impairing blood pressure regulation.
  • Just ONE night of only 4-5 hours of sleep can reduce daytime alertness and cognitive performance as much as going without sleep for up to 2 days straight.
  • Sleeping less than 5 hours per night on a regular basis appears to have the greatest adverse effects on blood pressure and cardiovascular risks.

So while occasional short nights of sleep likely won’t cause you to pass out, regularly not getting at least 6-7 hours can potentially increase the chances. Individuals at higher risk like people with low blood pressure or diabetes may feel effects with less sleep loss.

Other risks of chronic sleep deprivation

Fainting isn’t the only concern with ongoing lack of sleep. Not getting enough rest night after night can take a toll on nearly every system in the body. Some major risks include:

  • Weakened immune system and frequent illnesses
  • Obesity, weight gain, and diabetes
  • Mental health problems like depression, anxiety, and bipolar disorder
  • Impaired brain function and increased dementia risk
  • Higher risk of stroke, heart disease, and cardiovascular death
  • Increased risk of cancer
  • Earlier death

Impact of sleep deprivation by age group

Research has found that lack of sleep affects different age groups in different ways:

Age Group Effects of Sleep Deprivation
Infants and toddlers Impaired brain development, learning deficits, hyperactivity, behavior problems, weakened immunity
Children and teens Cognitive and memory impairment, behavior issues, mood changes, obesity and diabetes risk
Adults Fatigue, impaired concentration and productivity, mood changes, increased errors and accidents
Elderly Cognitive decline, confusion, impaired balance and coordination, increased risk of dementia and mortality

Tips for preventing fainting from lack of sleep

If you’re concerned about fainting or feeling lightheaded from not getting enough sleep, here are some tips that can help:

  • Prioritize getting at least 7-8 hours of sleep per night. Make sleep a priority and have a regular bedtime schedule.
  • Pay attention to signs you may be sleep deprived. Look for symptoms like needing coffee to get through the day, nodding off during monotonous tasks, and relying on alarms versus waking naturally.
  • Be cautious when changing position. Move slowly and gradually when getting up from lying or sitting to avoid blood pressure drops.
  • Increase fluid and salt intake. Drink enough water and consume adequate sodium if you are sleep deprived to prevent dehydration and low blood pressure.
  • Take note of other factors. Monitor your blood sugar levels, medication side effects, caffeine intake, and menstrual cycle since these can also influence fainting risk.
  • See your doctor if fainting continues. Get evaluated to identify any underlying disorders that need treatment.

When to see a doctor

Occasionally feeling lightheaded or dizzy when you haven’t slept much is usually not a major concern. However, you should seek medical care if you experience:

  • Fainting or actually losing consciousness
  • Passing out when standing up that’s new or worsening
  • Frequent spells of lightheadedness or dizziness
  • Unintentional weight loss, fever, or other signs of illness
  • Fainting along with chest pain, headache, or seizures
  • Injury during a fainting episode

Your doctor can check for underlying heart, neurological, or other disorders that may be causing syncope episodes. Treatment will depend on the cause but may include medication, compression stockings, increasing salt and fluids, or counseling for anxiety.


Research shows that lack of sleep can increase the risks of low blood pressure, dehydration, and blood sugar changes – which in turn makes fainting episodes more likely in some people. Adults who regularly get less than 5-6 hours of sleep per night appear most prone to these effects.

While passing out from sleep deprivation alone is uncommon in otherwise healthy people, individuals with existing low blood pressure, diabetes, or heart conditions may be more susceptible. Pay attention to signs your body needs more sleep like daytime fatigue. Prioritize getting adequate rest alongside other healthy habits to avoid fainting spells.