oMeds
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Answer · biomarkers

What causes chronic fatigue?

Short answer

Chronic fatigue has many causes — thyroid dysfunction, anemia, sleep disorders, depression, hormone deficiencies, chronic infection, autoimmune disease, and medications. A structured biomarker review narrows the differential.

Reviewed by Dr. Laura PurdyMay 29, 2026

Full answer

Chronic fatigue is a non-specific symptom with many possible drivers. A structured biomarker review screens for thyroid dysfunction (TSH, free T4, free T3), anemia (CBC, ferritin, iron studies, B12, folate), hormone deficiencies (testosterone, estradiol, cortisol AM, DHEA-S), metabolic patterns (fasting glucose, A1C, fasting insulin), inflammation (hs-CRP, ESR), and kidney/liver function. Sleep, medications, mood, and lifestyle history complete the evaluation. Within oMeds review, fatigue is rarely a single-marker problem; pathway selection follows from the pattern that emerges, not from a single low value.

Educational. Not a substitute for individualized provider review.

References & sources
  • TSH — Primary source · oMeds
  • Reviewed by Dr. Laura Purdy, MD, MBA · Clinical Director, oMeds · Last reviewed 2026-05-29

Related answers

What is TSH?
TSH (thyroid stimulating hormone) is the pituitary signal that drives thyroid hormone production. It is the most sensitive screening marker of thyroid function. Conventional ranges run roughly 0.4–4.5 mIU/L; many optimization frameworks target the lower-mid range when reading TSH with free T3, free T4, and TPO antibodies.
What is ferritin?
Ferritin is the body's primary iron storage protein. Low ferritin signals iron depletion — even before hemoglobin falls — and is implicated in fatigue, hair loss, and restless sleep. Ferritin is also an acute-phase reactant and can rise with inflammation.
Is TRT safe?
Provider-reviewed testosterone optimization is considered safe for most men with confirmed low testosterone when prescribed and monitored against a baseline biomarker panel. Safety depends on candidacy, dosing, delivery modality, and a recalibration cadence — not on the molecule alone.
Primary source
TSH