Hormones & HRT - Thyroid & fertility
Understanding TSH and thyroid blood tests
Last reviewed 3 August 2026. How we write this.
TSH and free thyroid hormones are interpreted together with symptoms, medication, illness and laboratory ranges.
A result just outside a range is not automatically a diagnosis. Biotin supplements can interfere with some thyroid assays.
Do not treat a number in isolation
Hyperthyroidism and hypothyroidism require different investigation; self-adjusting thyroid hormone can cause serious harm.
Educational content only. This does not diagnose, treat or replace individual advice from an appropriately qualified clinician.
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Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.