PCOS bloodwork: which tests to order
Polycystic ovary syndrome affects about 1 in 10 women, and a lot of people still do not get a complete workup. A useful PCOS lab panel should help with both diagnosis and ongoing management.
A useful PCOS workup usually needs more than reproductive hormones alone. On the hormone side, that tends to include androgens like testosterone and DHEA-S, plus reproductive hormones — LH, FSH, estradiol, progesterone, AMH, prolactin. On the metabolic side, fasting insulin, glucose, HbA1c, and a lipid panel matter, because insulin resistance shows up in a significant portion of PCOS cases.
A lot of people get told their labs look normal after only a basic metabolic panel and TSH. Free testosterone, DHEA-S, and fasting insulin are often missing from routine bloodwork, even though they tend to be among the more informative markers. The panel below pulls together the markers people often wish had been checked the first time.
Other conditions can look a lot like PCOS, so ruling those out matters too. 17-OH progesterone helps screen for non-classic congenital adrenal hyperplasia. TSH and Free T3 help evaluate thyroid function. Prolactin helps rule out pituitary-related causes of irregular cycles.
The complete PCOS panel
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Frequently asked questions
What blood tests diagnose PCOS?
PCOS is usually diagnosed using the Rotterdam criteria: two of the following three findings are present — irregular periods, elevated androgens, or polycystic ovaries on ultrasound. Common blood tests include total testosterone, free testosterone, DHEA-S, LH, FSH, and 17-OH progesterone. Many clinicians also look at AMH, fasting insulin, and HbA1c because insulin resistance is so common in PCOS.
Why is the LH:FSH ratio important in PCOS?
In classic PCOS, LH is often elevated while FSH stays normal or low, which can create an LH:FSH ratio above 2:1. That pattern can interfere with ovulation. A normal ratio does not rule out PCOS, though. The diagnosis depends on the full clinical picture, not one lab value.
Should I test insulin levels for PCOS?
Yes. Fasting insulin is often one of the most useful tests in a PCOS workup, especially when glucose and HbA1c still look normal. Many women with PCOS have insulin resistance, including some who are not overweight. An elevated fasting insulin can show up long before glucose markers become abnormal.
When in my cycle should I get PCOS labs drawn?
If your cycles are regular, LH, FSH, and estradiol are usually drawn on cycle days 2 through 4. Testosterone, DHEA-S, and insulin can usually be drawn at any time, though insulin should be fasting. If your cycles are irregular, timing is less predictable, so testing may be done whenever it is practical. AMH can be drawn at any point in the cycle.