Possible causes
- Sleep apnea – repeated pauses in breathing disrupt deep sleep, often without you knowing.
- Alcohol and late dinner – they raise night-time heart rate and reduce deep and REM sleep.
- Irregular schedule – shifting sleep at weekends disrupts your internal clock.
- Iron deficiency or anemia – low ferritin or hemoglobin often cause fatigue despite enough sleep.
- Thyroid – an underactive thyroid shows as fatigue, feeling cold and sluggishness.
- Stress and mood – depression and long-term stress often cause unrefreshing sleep.
What to check
- Ferritin and blood count – the basics for long-term fatigue.
- TSH and fT4 – to assess thyroid function.
- Vitamin D, B12 and glucose – common deficiencies or a hidden metabolic problem.
- Breathing during sleep – ask your partner about snoring and breathing pauses; a wearable may show high night-time heart rate and drops in oxygen saturation.
What helps
- Regular sleep times – the same wake-up time 7 days a week.
- Last meal 2–3 hours before bed – and alcohol only occasionally.
- Morning light and movement – daylight and light activity in the morning improve waking up and falling asleep at night.
- An optimal bedroom – cool, dark, quiet; the bed for sleep, not work.
- Gentle waking – an alarm without repeated snoozing; sleep inertia usually fades within 30 minutes.
When to see a doctor
See a doctor if you snore, your partner notices pauses in breathing, you wake with headaches or a dry mouth, fall asleep during the day or at the wheel, or if fatigue persists for more than a few weeks despite changing your routine.