The blood tests that actually matter for PCOS

PCOS is often reduced, in conversation, to "a hormone imbalance" — which isn't a wrong description so much as an incomplete one. A proper pathology work-up looks at several distinct systems, because the condition affects more than reproductive hormones.

Androgens and SHBG

Testosterone and other androgens are checked because elevated levels are one of the core diagnostic features of PCOS, linked to acne, excess hair growth, and cycle irregularity. Sex hormone-binding globulin (SHBG) is checked alongside it — SHBG affects how much androgen is actually "free" and active in the body, so the two are read together, not separately.

LH, FSH, and prolactin

Luteinising hormone (LH) and follicle-stimulating hormone (FSH) help characterise the pattern of irregular ovulation, and an elevated LH:FSH ratio is a common (though not universal) PCOS finding. Prolactin and thyroid function (TSH) are checked to rule out other conditions that can cause irregular periods and mimic PCOS — an important step, because treating the wrong underlying cause doesn't help.

The metabolic panel — the part that's easy to skip

Fasting glucose and fasting insulin are checked because insulin resistance is present in a large proportion of people with PCOS, including many who aren't in a higher weight range — a detail that gets missed when PCOS is assumed to only affect people who are overweight. A lipid panel is included because PCOS is associated with a higher long-term cardiovascular risk. This is often the part of a PCOS work-up that gets skipped in a rushed appointment, even though it's arguably the part with the most long-term relevance.

Why this needs revisiting, not just running once

None of these markers are static — androgens, insulin sensitivity, and cycle patterns can all shift with time, treatment, and life stage. A panel run once at diagnosis and never repeated only tells you where things stood on that day.

This is general health information and not medical advice. Your doctor will discuss your specific situation during a consultation.