Fertility Library
Fertility hormone blood tests: FSH, LH, oestradiol, prolactin and thyroid
A practical guide to common reproductive hormone tests and why timing and context matter.
Why these tests differ
FSH and LH are involved in reproductive signalling, oestradiol changes across the menstrual cycle, prolactin can influence ovulation and thyroid hormones support many bodily processes. No single panel diagnoses every fertility issue.
Timing matters
Some reproductive hormones vary substantially across a cycle, so the timing of a blood sample can matter. Results should be interpreted with cycle history, symptoms, medications and laboratory ranges.
Avoid the checklist trap
More tests are not always better. The best next test depends on the clinical question, including irregular periods, suspected ovulatory difficulties or symptoms of thyroid dysfunction.
Discussing results
Bring the original report with units, reference intervals and the date taken. Ask what the finding does and does not establish and whether repeat testing or specialist review is appropriate.
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Fertility Barrier Finder can help organise your history and highlight possible areas and investigations to discuss with a qualified healthcare professional. It cannot diagnose a fertility condition, confirm a barrier or predict pregnancy.
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Find my fertility barriersMore fertility guides
What does an AMH test tell you about fertility? · Fertility hormone blood tests: FSH, LH, oestradiol, prolactin and thyroid · Irregular periods and ovulation: what might be worth checking? · Male fertility tests: when might more than a semen analysis be needed? · When should you seek fertility advice? Age, timing and other reasons · A fertility investigation checklist for couples: where to begin · Unexplained infertility: what does it mean and what happens next?