What blood tests diagnose PCOS?
Here's the honest answer: no blood test diagnoses PCOS on its own. Tests support an assessment that also relies on your symptoms, your cycle pattern and the exclusion of other conditions — they're pieces of a picture, not a verdict. That said, certain tests do come up regularly when PCOS is being considered.
Which tests tend to come up
When PCOS is being assessed, blood tests often include hormones related to androgens — testosterone and SHBG, sometimes expressed as a free androgen index — and tests used to rule other conditions out, such as thyroid function (TSH) and prolactin. LH and FSH are sometimes checked, and metabolic tests like glucose may feature as part of wider care. The NHS describes hormone tests as part of the diagnostic process. Which tests are done is a clinical decision, and we don't quote reference ranges or numbers — interpretation belongs with the clinician who ordered them.
Why the results need keeping
Because no single result settles things, the value is in the whole panel read together — and in how it changes over time. Yet these results scatter across GP systems, hospital portals and printouts, easily lost when you move practice. Keeping your own dated record of each result means that when a clinician asks what your testosterone or thyroid looked like last time, you can answer with a figure and a date rather than a guess.
PCOS Diary keeps each blood result dated in a lab vault, so the whole panel reads together — and over time — in a doctor-ready PDF.
Common questions
- Is there one blood test that confirms PCOS?
- No. PCOS is assessed from a combination of symptoms, cycle pattern and tests, with other conditions excluded — no single blood test confirms it. Tests support the picture a clinician builds; they don't decide it alone.
- Why are thyroid and prolactin tests done for PCOS?
- Because other conditions can cause similar symptoms, tests like thyroid function and prolactin help rule those alternatives out — which is part of how PCOS is diagnosed. Seeing them on a form usually means your clinician is being thorough.
- Why keep my own copy if the surgery already holds the results?
- Because the surgery's copy isn't always to hand when you need it. Results sit across GP systems and hospital portals, and they don't always follow you when you move practice or see someone new. A clinician who asks what your testosterone or thyroid looked like last time can be answered straight away if you've kept the figure and the date yourself, rather than waiting on a records request. Over months that own copy also lets the whole panel be read together and against earlier readings, which is where its real value sits.