Understanding Your Lab Tests for PCOS

Is It PCOS or Another Health Condition?

Nurse taking blood from patient, close up
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When a woman has PCOS, she may be experiencing any number of symptoms, like irregular menstrual cycles or signs of high androgen levels like acne and abnormal hair growth (hirsutism). If a woman stops menstruating and/or her doctor suspects a diagnosis PCOS, a number of blood tests are classically run. This is to ensure that something else is not going on, like an underactive thyroid gland or a rare androgen-secreting tumor.

It's important to note that a person's history and physical exam are helpful in making the diagnosis of PCOS, and your doctor will use both your blood tests and your exam to piece together the diagnosis. As of now, there is no single slam-dunk blood test to diagnosis PCOS.

In addition, remember that if you have missed your period or stopped menstruating, you can bet that the first test your doctor will do is a pregnancy test -- so do not be surprised about this, even if you are certain you are not pregnant. After that is confirmed negative, your doctor will move forward with other blood tests.

What is the FSH/LH Blood Test?

Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) are produced and released by the pituitary gland -- a pea-sized gland located at the base of the brain. FSH stimulates the growth of an egg follicle within the ovary, while the surge of LH triggers the release of the egg during ovulation.


Previous diagnoses of PCOS were made based on an LH to FSH ratio of greater than 3:1. This is not the case anymore because while many women with PCOS have persistently elevated LH levels throughout their entire cycle, it's not uncommon for some women with PCOS to have normal hormone values. Still, women with PCOS typically will have FSH levels that are lower than the LH level -- so, again, this can support a diagnosis of PCOS, but not confirm it.

Also, if FSH is elevated, it can be an indication of a condition called premature ovarian insufficiency.

What is the DHEA/Testosterone Blood Test?

Dehydroepiandrosterone (DHEA) and testosterone are two of the androgens or male hormones. These androgens are responsible for many of the male secondary sex characteristics like abnormal hair growth or loss and acne, which explains the symptoms that PCOS sufferers experience. They also cause menstrual irregularities in women.

While elevation of testosterone is typical in women with PCOS, it's important to note that women can have signs of high androgen levels (acne, hair growth) but have normal androgen levels on their blood test -- and still have PCOS. In other words, a doctor has to put together your physical exam with your labs to make the diagnosis.

Rarely, a very high testosterone levels could be a sign of an androgen-secreting tumor of the ovary. Likewise, high DHEA levels could be a sign of an androgen-secreting tumor of the adrenal gland (small glands that sit upon your kidneys).

What is the 17-hydroxyprogesterone Blood Test?

This blood test is used to determine the presence of late-onset congenital adrenal hyperplasia, another medical condition that can mimic the symptoms of PCOS.

What is a Thyroid Function Blood Test?

These tests are used to rule out thyroid dysfunction as a cause of menstrual irregularity. Thyroid Stimulating Hormone (TSH) is also secreted by the pituitary gland and controls the release of the two thyroid hormones T3 and T4. These two hormones control basic metabolism and could produce menstrual changes similar to those in PCOS. Either higher or lower than normal lab values could indicate thyroid disease and should be followed up.

What is a Prolactin Blood Test?

Secreted by the pituitary, this hormone’s primary responsibility is promoting lactation in women.

Elevated values can cause a lack of menstruation. If elevated, your doctor will test your thyroid (if not already) as untreated hypothyroidism can cause an elevated prolactin level. In addition, your doctor will order an MRI of the pituitary gland to evaluate for a tumor called a prolactinoma.

Blood Tests When Diagnosed with PCOS

Once you have been diagnosed with PCOS, your doctor will want to evaluate you for type 2 diabetes and high cholesterol levels, which are common metabolic abnormalities in women with PCOS.

  •  Glucose Tolerance Test (GTT): This test will allow your physician to measure your response to a sugar stimulus. Insulin is the major hormone which deals with sugar and fuel within the body. The examiner will give you a very sweet, sugary solution to drink. Blood tests will be drawn before the test begins and at one and two hours afterward. Urine samples may be collected as well to measure glucose in the urine. It's important to not eat or drink anything once the test begins, or for 12 hours before, as it will affect the results. Normally, blood sugar should return to normal within 2 hours. If blood sugar levels are elevated beyond the test, it may indicate that your body does not respond as quickly to insulin -- indicating a diagnosis of prediabetes or diabetes. Your doctor may confirm this abnormal finding by repeating the test.

  • Cholesterol Test: This test is sometimes referred to as a lipid panel. Women with PCOS can have high cholesterol. Because of the association of PCOS with metabolic disturbances, including heart disease and diabetes, it's important to monitor your cholesterol and blood pressure. This will allow your practitioner to quickly treat you if you develop risk factors for cardiac disease and minimize their effects.

Bottom Line

While it may seem like your doctor is ordering a number of blood tests, don't be alarmed. This is common protocol and is done to ensure that the right diagnosis is made so you can move forward with the appropriate care and treatment. 


Sheehan, M.T. Polycystic Ovarian Syndrome: Diagnosis and Management. Clinical Medicine & Research, Feb;21(1):13-27.

Sirmans, S.M., Pate, K.A. (2014). Epidemiology, diagnosis, and management of polycystic ovary syndrome. Journal of Clinical Epidemiology, 6:1-13.

DISCLAIMER: The information in this site is for educational purposes only. It should not be used as a substitute for personal care by a licensed physician. Please see your doctor for diagnosis and treatment of any concerning symptoms or medical condition.

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