Polycystic ovary syndrome (PCOS) blood test

First line

Polycystic ovary syndrome (PCOS) blood test covering the cycle, androgens and metabolism. It includes thyroid, prolactin, FSH, LH, oestradiol, progesterone, testosterone, SHBG, DHEA-S, androstenedione, 17-OH progesterone, glucose, insulin, HOMA-IR, glycated haemoglobin and cholesterol. It helps investigate the syndrome and several conditions that can look similar.

No prescription or appointment needed

Results in 3-5 working days

Includes: TSH · Free T4 · Pooled prolactin · FSH · LH · Oestradiol · Progesterone · Total testosterone · SHBG · Albumin · Free androgen index · DHEA-S. 19 in total. See what each one measures

What it is for

It looks at three things. First, whether there is androgen excess in someone with irregular periods, acne or hirsutism, that is, increased hair growth in a male pattern. Second, whether there are other hormonal causes that mimic PCOS, such as thyroid, prolactin or 17-OH progesterone abnormalities. Third, whether there are associated metabolic changes in glucose, insulin or cholesterol.

The blood test does not diagnose the syndrome on its own. In adult women, clinical and hormonal criteria and, depending on the case, ultrasound or AMH are required, after excluding alternative diagnoses. In adolescents stricter criteria apply, and ovarian morphology is not used in the same way.

When it is recommended

Irregular or widely spaced periods together with increased hair growth or persistent acne
Suspected polycystic ovary syndrome already raised at a medical assessment
Difficulty getting pregnant with irregular cycles
A previous PCOS diagnosis without a recent metabolic assessment
Irregular cycles together with a family history of type 2 diabetes

Clinical comment

The name polycystic ovary syndrome is still the one most people know and search for, even though the condition is not limited to the ovary and does not require having "cysts". The disturbance can be reproductive, androgenic and metabolic, which is why we have kept all three blocks in the profile.

17-OH progesterone helps exclude non-classic congenital adrenal hyperplasia, which can cause irregular periods and androgen excess. Prolactin and the thyroid follow the same logic: before attributing the picture to PCOS, causes that are managed differently have to be assessed.

The free androgen index is calculated from total testosterone and SHBG. It gives more context than an isolated total testosterone, but the results depend on the quality of the laboratory method and on contraceptives, which can raise SHBG considerably.

Bear in mind that the LH/FSH ratio is not part of the current diagnostic criteria. Nor does HOMA-IR have a universal cut-off. It is included to describe the metabolic context, while the assessment for diabetes relies mainly on glucose, HbA1c and, where appropriate, a glucose tolerance test.

Dr. Antonio Mas

What is tested

TSH: Used to check whether a thyroid disorder is behind irregular periods.
Free T4: Completes the thyroid assessment.
Pooled prolactin: Looks for hyperprolactinaemia that could disrupt the cycle.
FSH: Gives information about the ovarian axis and helps assess alternative diagnoses.
LH: Involved in ovulation and interpreted together with FSH and oestradiol.
Oestradiol: Reflects oestrogen production by the ovary.
Progesterone: Gives a baseline value when measured at the start of the cycle. To confirm ovulation it has to be requested in the luteal phase, not on days 2 to 5.
Total testosterone: One of the main androgens used to assess biochemical hyperandrogenism.
SHBG: The protein that carries sex hormones and determines how much testosterone is available.
Albumin: Completes the picture of hormone transport and allows other calculations when they are required.
Free androgen index (calculated): Estimates insulin resistance from glucose and insulin.
DHEA-S: An androgen that comes mainly from the adrenal glands.
Androstenedione: Completes the assessment of androgen excess of ovarian or adrenal origin.
17-OH progesterone: Used to exclude non-classic congenital adrenal hyperplasia.
Glucose: Measures fasting blood sugar.
Insulin: Shows how much insulin is circulating to keep glucose stable.
HOMA-IR index (calculated): Estimates insulin resistance from glucose and insulin.
Glycated haemoglobin (HbA1c): Reflects average glucose over the last two or three months.
Lipid profile (total cholesterol, HDL, LDL, triglycerides) and ratios

These tests are used to calculate Índice HOMA-IR and Testosterona libre calculada. They are not separate tests.

How to prepare

Have the sample taken between days 2 and 5 of the cycle, in the morning, after fasting for 8 to 12 hours. If you do not have periods, it can be done on any day. Avoid intense exercise the day before and arrive with time for the pooled prolactin.

If you use contraceptives or another hormonal treatment, say so before the test. They change SHBG, androgens and the cycle, but they should not be stopped on your own initiative.

You can add

Without another needle. It is offered when you order, so you do not have to decide now.

General blood testA general blood test with full blood count, glucose, cholesterol and kidney and liver function: the basic parameters included in any general check-up.+€59.00
Glucose tolerance test (oral glucose load)Shows how the body responds to a glucose load when fasting glucose or glycated haemoglobin leave doubts; it requires staying at the laboratory for two hours.+€49.00
Anti-Müllerian hormone (AMH)Gives an indication of ovarian reserve, that is, the number of follicles available, and helps anticipate how the ovaries will respond in fertility treatment.+€79.00

Related blood tests

We have other profiles in Women with more or fewer tests:

The most comprehensive is not always the most useful. This is the one we recommend to start with; the others cover specific situations.

What it is based on

J Clin Endocrinol Metab 108(10):2447-2469
Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome
It calls for assessing androgen excess with total and free testosterone, and accepts estimating free testosterone through the calculated free androgen index. It also recommends preferring mass spectrometry to direct immunoassay, which has poor sensitivity and poor precision for measuring androgens in women.

Protocol designed by Dr. Antonio Mas, specialist in Endocrinology and Nutrition, Spanish medical licence no. 080846289, and reviewed in September 2026.

This blood test is a standardised protocol and does not replace a medical consultation. If you have symptoms, a known condition or a complex clinical situation, speak to your doctor.