Understanding Your Lab Tests for PCOS

If you experience symptoms of polycystic ovary syndrome (PCOS), a healthcare provider may order a number of tests to determine whether they're caused by PCOS or some other condition is involved, such as an underactive thyroid gland (hypothyroidism).

Unlike other medical conditions, diagnosing PCOS is mainly based on a process of elimination. There is no single blood test that can diagnose the disease. Rather, a healthcare provider will accumulate evidence from blood work, along with imaging studies and a pelvic exam, to help support the diagnosis of PCOS.

This article provides information on how to understand lab tests for a PCOS diagnosis.

Diagnostic Blood Tests

If you've missed your period or have stopped menstruating, the first test your healthcare provider will likely do is a pregnancy test to ensure that pregnancy is not the cause. If the test is negative, your healthcare provider will move forward with other blood works.

FSH/LH Blood Test

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are produced by the pituitary gland, a pea-sized organ located at the base of your 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. 

In the past, the diagnosis of PCOS was made based on an LH-to-FSH ratio greater than 3-to-1 (3:1). This is not the case anymore since many women with PCOS have persistently elevated LH levels throughout their entire cycle and otherwise normal hormone levels.

Also, if your FSH is elevated, it may be an indication of an unrelated condition called primary ovarian insufficiency.

17-Hydroxyprogesterone Test

This blood test, also known as 17-OHP, is used to detect a hormone produced by the adrenal glands that is involved in the production of the stress hormone cortisol. The test is used to determine the presence of late-onset congenital adrenal hyperplasia, another medical condition that can mimic the symptoms of PCOS.

DHEA/Testosterone Blood Test

Dehydroepiandrosterone (DHEA) and testosterone belong to a class of hormones known as androgens (a.k.a. male hormones). They are responsible for secondary male sex characteristics and are the cause of many of the symptoms of PCOS, including acne, hirsutism, female-pattern baldness, and menstrual irregularities.

While the elevation of testosterone is typical in women with PCOS, it is possible to have a spontaneous outbreak of acne and hirsutism with normal androgen levels and still be diagnosed PCOS. As such, androgen irregularities are a guide by which PCOs is diagnosed, but they aren't a hard-and-fast rule.

Thyroid Function Tests

This panel of blood tests is used to rule out thyroid dysfunction as a cause of your menstrual irregularity. Thyroid-stimulating hormone (TSH) is also secreted by the pituitary gland and regulates the release of the two thyroid hormones, called triiodothyronine (T3) and thyroxine (T4).

These two hormones regulate basic metabolic function. Low levels of either could produce menstrual changes similar to those experienced in women with PCOS.

Prolactin Test

Prolactin is a hormone secreted by the pituitary gland whose primary role is promoting lactation in women. Elevated values of this hormone (referred to as hyperprolactinemia) can cause irregular menstruation (oligomenorrhea) or a total lack of menstruation (amenorrhea).

If levels of prolactin in your blood are elevated, your healthcare provider will test your thyroid function since untreated hypothyroidism can also cause elevated prolactin. Your healthcare provider will also likely order a magnetic resonance imaging (MRI) scan of the pituitary gland to see whether a tumor called a prolactinoma is involved.

Blood Tests for Co-Occurring Conditions

If you are diagnosed with PCOS, your healthcare provider will want to investigate whether you have type 2 diabetes and high cholesterol both of which are common in women with PCOS.

Oral Glucose Tolerance Test

An oral glucose tolerance test (OGTT) measures your response to sugar. Insulin is the major hormone that regulates blood sugar (glucose) and the way it is metabolized for energy. For the OGTT, you will be given a very sweet, sugary solution to drink. Blood tests will be drawn before the test and one and two hours after. Urine samples may be collected as well.

In people without diabetes, the blood sugar should return to normal within two hours. If not, the test may be indicative of prediabetes or diabetes.

Lipid Panel

A cholesterol test, also referred to as a lipid panel, measures all of the key values associated with high cholesterol, including total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and another type of lipid known as a triglyceride.

Women with PCOS often high cholesterol, which can increase the risk of heart disease and diabetes.

A Word From Verywell

While it may seem like your healthcare provider is ordering a lot of blood tests to diagnose PCOS, this is perfectly normal and no cause for alarm. The more tests your healthcare provider performs to confirm the disorder—and rule out others—the better equipped they will be in dispensing the correct treatment.