PCOS: which tests actually help, and when in your cycle to give them

PCOS is one of the most common hormonal conditions in Indian women, and one of the most confusingly tested. Results are read against the day of your cycle, so the same number can mean different things depending on when the sample was taken.

Timing changes the answer

FSH and LH are conventionally taken on day 2 or 3 of your cycle, counting the first day of bleeding as day 1. Taken mid-cycle they can look dramatically abnormal in a completely normal cycle.

Progesterone is taken around day 21 of a 28-day cycle, because its job is to confirm whether ovulation happened. On day 3 it tells you almost nothing.

AMH can be given on any day, which is part of why it is useful when cycles are irregular enough that "day 3" is not meaningful.

If your cycles are very irregular, say so — your doctor may ask for the sample at a specific point or after inducing a bleed.

What is usually checked

• FSH and LH — the pituitary hormones driving ovulation
• AMH — ovarian reserve, and often raised in PCOS
• Testosterone and DHEA-S — androgens, which explain acne and unwanted hair growth
• Prolactin — a common alternative explanation for irregular periods
• Thyroid — another common alternative explanation, and easily missed
• Fasting insulin and glucose — see below

Why insulin belongs in the conversation

PCOS is very often accompanied by insulin resistance, and this is the part most commonly left out. Sugar can read completely normal for years while insulin is already working far harder than it should to keep it there.

That matters because it changes treatment. Managing insulin resistance — through diet, weight, exercise and sometimes medication — often improves the periods, the skin and the fertility outcomes together, rather than treating each symptom separately.

If insulin has never been checked, it is a reasonable thing to ask about.

What a scan adds

An ultrasound looks at the ovaries and the uterine lining. "Polycystic-appearing ovaries" on a scan is a finding, not a diagnosis on its own — plenty of women have that appearance without PCOS, and some women with PCOS do not show it. Diagnosis combines the scan with symptoms and blood results.

What to bring

Your doctor will want the date your last period started, how long your cycles usually run and how much they vary. That single piece of information changes how every result above is interpreted, and it is the one most often forgotten on the day.

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General information, not medical advice. PCOS is diagnosed by a doctor combining symptoms, examination, blood results and imaging.