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Health effect

Fatigue

A guide to persistent tiredness and when iron deficiency matters.

Energy

What can cause fatigue?

Sleep problems, stress, depression, hormonal changes, infections, and medicines can contribute to tiredness. Persistent unexplained fatigue can also indicate an underlying illness. 1

When should it be assessed?

Medical assessment is recommended when tiredness lasts several weeks without explanation or disrupts daily life. Blood tests may check for anemia, diabetes, or thyroid disease. 1

What can help?

Treatment depends on the cause. Sleep support, relaxation strategies, and appropriate psychological care may be relevant. 1

Nutrients with the strongest ratings

Sorted by the largest rated effect. Bars show effect size, the letter is the evidence grade.

IronNot rated–
Vitamin B12Not rated–
Every ratingEvery nutrient rated for fatigue, with search

What does the evidence cover?

This section covers the specific uses below; other supplements are not reviewed.

IronMixed

Iron deficiency can cause fatigue and can be treated with iron preparations. The underlying cause, such as blood loss, also needs attention. DGE does not recommend routine iron supplementation for everyone. 2 3

Questions people ask

Does fatigue mean iron deficiency?

No. Sleep problems, stress, infections, and other illnesses can also cause tiredness. 1

Can blood loss cause iron deficiency?

Yes, including heavy menstrual bleeding. 2

Should everyone take iron?

DGE does not recommend general iron supplementation. 3

When should I see a doctor?

When unexplained tiredness persists for weeks or affects daily life. 1

Sources