Feeling like you could sleep all day, with no energy for anything, has many possible causes, from everyday ones to medical conditions that need a test to identify. This page sets out what official health sources say, without guessing which one applies to you.

Quick Answer (TL;DR)

The most common causes are not getting enough sleep, sleeping badly, and lifestyle factors such as stress. Some medical conditions can also cause constant tiredness, including iron deficiency anaemia, thyroid problems, diabetes, sleep apnoea and depression. Only a doctor can tell which applies, often with blood tests. The NHS advises seeing a GP if you’ve been tired for a few weeks and don’t know why.

Key Takeaways

  • Not enough sleep, insomnia and an unhealthy lifestyle are common causes of tiredness, according to the NHS. So are stress, low mood and hormonal changes such as pregnancy or the menopause (NHS).
  • Several medical conditions can cause it, and blood tests can check for some of them, such as anaemia, diabetes and thyroid problems (NHS).
  • Sleep apnea lists daytime sleepiness and tiredness among its symptoms, along with loud snoring and gasping during sleep. Not everyone who snores has it (NHLBI).
  • Fatigue and lack of energy are common signs of depression (NIMH).
  • Don’t self-diagnose. The NHS advises seeing a GP rather than trying to work out the cause alone.

Everyday Causes

The NHS lists these as common causes of tiredness (NHS, Tiredness and fatigue):

  • Not getting enough sleep, or finding it hard to get to sleep (insomnia)
  • An unhealthy lifestyle
  • Stress and low mood
  • Hormonal changes, such as pregnancy or the menopause

The first one is easy to underestimate. Adults aged 18 to 60 are recommended to sleep at least 7 hours a night on a regular basis; see how much sleep you need by age. If you are in bed long enough and still wake up tired, see why you can be tired after 8 hours of sleep.

Medical Conditions That Can Cause Tiredness

The conditions below are possibilities a doctor may consider, not a checklist for diagnosing yourself. Many share the same symptoms, which is why tests are needed.

  • Iron deficiency anaemia. The NHS lists it among the physical causes of tiredness; a blood test can check for it (NHS).
  • Thyroid problems and diabetes. Blood tests can check for these too (NHS).
  • Sleep apnoea. The NHLBI lists breathing that stops and starts during sleep, frequent loud snoring and gasping for air, as well as daytime sleepiness, tiredness and headache. You may not know about the night-time symptoms until someone tells you. Not everyone who snores has sleep apnea, and only a sleep study can diagnose it (NHLBI). More: does snoring mean sleep apnea?
  • Depression. The NIMH lists fatigue, lack of energy or feeling slowed down, and changes in sleep, among common signs. For a diagnosis, symptoms are present most of the day, nearly every day, for at least two weeks (NIMH).
  • ME/CFS. Myalgic encephalomyelitis, or chronic fatigue syndrome, is a long-term condition whose symptoms include extreme tiredness (NHS).
  • Idiopathic hypersomnia. A rare neurological sleep disorder. People have a hard time staying awake during the day and may find it hard to wake up, and sleeping longer at night doesn’t appear to improve the daytime sleepiness (NIH GARD).

Sleepy or Fatigued?

People use “tired” for two different feelings:

  • Sleepiness is struggling to stay awake: dozing off, or wanting to nap.
  • Fatigue is a lack of energy, even if you could not actually fall asleep.

The causes above can produce either one, or both. For a related pattern, sleepy all day but wide awake at night, see why you can be sleepy all day but can’t sleep at night.

How to See Your Own Nights

One of the NHS reasons to see a GP, gasping or choking noises in your sleep, happens while you’re asleep, so you usually only know about it if someone tells you. A record of your nights gives you something concrete to bring.

With Snollo, you tap Start at bedtime and the app records the night on your iPhone. It records snoring and other sounds and lets you play them back, so you have something concrete to show a doctor. The free tier keeps your full sleep history. Sleep stages are most accurate with an Apple Watch. Without one, Snollo estimates approximate stages from the iPhone’s microphone and motion sensors, with the iPhone on the mattress near you. Phone and watch stages are estimates; the most accurate way to measure sleep stages is an overnight sleep study (polysomnography), which records brain waves (EEG), eye movements (EOG) and muscle tone (EMG) (NHLBI). Snollo is not a medical device and does not diagnose any condition, including sleep apnea. If you’re concerned about apnea, the sleep apnea risk questionnaire is a validated screener to bring to that conversation.

Download Snollo free on the App Store

When to See a GP

The NHS advises booking a non-urgent GP appointment if (NHS):

  • you’ve been tired for a few weeks and don’t know why;
  • tiredness is affecting your daily life;
  • you have other symptoms, such as weight loss or changes in mood;
  • someone has told you that you make gasping or choking noises in your sleep.

Frequently Asked Questions

Why am I always tired even when I sleep a lot?

Long sleep that still leaves you tired can have several causes, including poor-quality sleep (for example from sleep apnoea), low mood or depression, and medical conditions such as anaemia or thyroid problems. A rare sleep disorder, idiopathic hypersomnia, also causes daytime sleepiness that longer sleep doesn’t appear to fix. Only a doctor can work out which applies, so the NHS advises seeing a GP if you’ve been tired for a few weeks without knowing why.

Can sleep apnea make you tired all the time?

Daytime sleepiness and tiredness are among the listed symptoms of sleep apnea, together with loud snoring, gasping for air and breathing that stops and starts during sleep. Not everyone who snores has sleep apnea, and only a sleep study can diagnose it.

What blood tests check for tiredness?

The NHS says blood tests can check for conditions such as anaemia, diabetes and thyroid problems. Which tests are needed is for your GP to decide, based on your symptoms.

Is it normal to want to sleep all day?

Feeling sleepy after a few short or broken nights is common. Wanting to sleep all day for weeks, without knowing why, is something the NHS says to raise with a GP, especially if it affects your daily life or comes with other symptoms such as weight loss or mood changes.

Snollo does not diagnose or treat any medical condition. This article summarizes guidance from official health sources for general information. If you are worried about your tiredness, talk to a doctor. If you have any doubts about how you feel or how you sleep, talk to a doctor or sleep specialist.

Sources

Sources
  1. Tiredness and fatigue — NHS
  2. Sleep Apnea: Symptoms — National Heart, Lung, and Blood Institute
  3. Depression — National Institute of Mental Health
  4. Idiopathic hypersomnia — Genetic and Rare Diseases Information Center (GARD), NIH
  5. Myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS) — NHS
  6. Sleep Studies — National Heart, Lung, and Blood Institute