Why am I
always tired?

Rule out the medical causes first — iron deficiency, thyroid problems, sleep apnoea, coeliac disease, diabetes and depression are common, treatable and easily missed. If those are clear, the usual lifestyle culprits are chronic sleep debt, eating too little, too much training with too little recovery, and alcohol.

Start with the things a GP can test for

This is genuinely the first step, not a disclaimer. Persistent fatigue is one of the most common presenting symptoms in general practice, and a standard blood panel finds a cause often enough to be worth doing before you rearrange your life around a theory.

Cause	Often also	How it is found
Iron deficiency / anaemia	Breathlessness, pale skin, cold hands	Full blood count, ferritin
Underactive thyroid	Weight gain, feeling cold, dry skin	TSH
Sleep apnoea	Snoring, morning headache, unrefreshing sleep	Sleep study referral
Coeliac disease	Bloating, altered bowel habit	Coeliac serology
Type 2 diabetes	Thirst, frequent urination	HbA1c
Vitamin D deficiency	Aching muscles, low mood	Blood test
Depression or anxiety	Low interest, poor sleep, low appetite	GP conversation

Iron deficiency deserves a special mention for anyone who menstruates or trains endurance: it is very common, it produces exactly this symptom, and it is invisible unless somebody measures ferritin.

Chronic sleep debt

Six and a half hours a night for a month is not a shorter version of eight hours — it accumulates. The effect is insidious because subjective alertness plateaus while performance continues to fall, so you stop noticing that you are impaired.

The test is simple: give yourself two weeks with an extra hour in bed. If the tiredness lifts, the diagnosis was sleep debt and the treatment is more time asleep, not a better sleep score.

Eating too little, or too little of the right thing

Under-eating is a very common cause of tiredness among people who are actively trying to be healthy, which is why it goes unsuspected. Three specific versions:

• Too few total calories. An aggressive deficit reliably produces fatigue, cold hands, poor training and worse sleep. If tiredness arrived with the diet, the diet is the cause.
• Carbohydrate too low for the training load. Very common in people who both lift and run. Low carbohydrate availability feels exactly like being tired all the time.
• Long gaps without eating. Not harmful in itself, but if every afternoon collapses at four o’clock, look at what lunch was made of.

Training more than you are recovering from

Fatigue from training is supposed to be temporary. When it stops being temporary, the pattern is recognisable: sessions feel heavier at the same loads, resting heart rate drifts up a few beats, sleep gets worse rather than better, and motivation goes before performance does.

The fix is rarely to stop entirely. Cutting volume by a third for a week while keeping intensity is usually enough, and it tells you within days whether training load was the problem.

Alcohol, and how much it actually costs

Alcohol is a sedative, not a sleep aid. It shortens the time to fall asleep and then degrades the second half of the night, suppressing REM and raising heart rate for hours. Two or three drinks on a Friday can still be visible in overnight heart rate on Sunday. It is one of the few variables where the wearable data is unambiguous.

A two-week diagnostic

1. Book the blood tests. Do not wait for the other steps.
2. Add an hour in bed, and keep the wake time fixed.
3. Log food for two weeks without changing it, then look at calories, protein and carbohydrate honestly.
4. Drop training volume by a third, keeping the weights heavy.
5. Remove alcohol entirely for the fortnight.
6. Note resting heart rate each morning. A downward trend means recovery is winning.

Change all five at once. This is not a science experiment, it is an attempt to feel better; if it works you can reintroduce things one at a time afterwards and find out which one mattered.

Common questions

Why am I always tired even after 8 hours of sleep?

If sleep duration is adequate, the common causes are iron deficiency, an underactive thyroid, sleep apnoea that fragments sleep without waking you, eating too little for your activity level, accumulated training fatigue, or alcohol. A blood test rules out several of these quickly.

Can eating too little make you tired?

Yes, and it is one of the most frequently missed causes among people actively trying to be healthy. An aggressive calorie deficit, or carbohydrate intake well below what the training load requires, produces persistent fatigue, poor sessions and disrupted sleep.

How do I know if I am overtrained?

The usual pattern is the same loads feeling heavier, resting heart rate drifting upward by several beats, sleep worsening rather than improving, and motivation dropping before performance does. Reducing volume by about a third for a week while keeping intensity usually confirms it.

When should I see a doctor about tiredness?

If tiredness has lasted more than a few weeks, is not explained by sleep or workload, or comes with weight change, breathlessness, low mood, persistent thirst or altered bowel habit. Ask for a full blood count, ferritin, TSH, HbA1c and vitamin D.

Persistent tiredness can be a symptom of a treatable medical condition, including iron deficiency, thyroid disorders, sleep apnoea, coeliac disease, diabetes and depression. If tiredness has lasted more than a few weeks, see a GP and ask for blood tests before assuming it is lifestyle.

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