Why am I tired all the time?

Persistent tiredness is one of the most common reasons people see a doctor. The cause is often a mix of small things — but sometimes it's a sign worth investigating.

1. Not enough (or poor-quality) sleep

The American Academy of Sleep Medicine and Sleep Research Society recommend at least 7 hours a night for adults. Irregular schedules, late screen use, alcohol and caffeine late in the day all erode sleep quality. Start with how much sleep adults need.

2. Stress and mental load

Chronic stress keeps the body in a heightened state, disrupting sleep and draining energy. Low mood and depression also commonly show up as fatigue.

3. Too little movement

It sounds backwards, but inactivity tends to lower energy. Regular moderate activity is associated with better sleep and less fatigue.

4. Diet and hydration

Skipping meals, relying on refined carbs, and not drinking enough can leave you sluggish. Heavy alcohol use is another common culprit.

5. Medical causes

Several common conditions cause fatigue:

• Iron deficiency or anemia — especially in people who menstruate.
• Low vitamin B12 — the NIH Office of Dietary Supplements lists fatigue and weakness among the signs, with higher risk for older adults, people on metformin or acid-reducing drugs, and those on vegan diets.
• Thyroid problems, diabetes and sleep apnea.
• Side effects of medications.

What to do next

Track your sleep, caffeine, alcohol and activity for two weeks. Tighten your sleep routine, get daylight in the morning, and move daily. If tiredness persists beyond a few weeks, or comes with weight change, low mood, or shortness of breath, see a clinician for a check-up and blood tests.

For more daily strategies, read our energy optimization guide and sleep optimization hub.