Getting tested for PCOS typically involves a combination of blood work, a physical exam, and sometimes an ultrasound or a specific blood marker called AMH. There’s no single test that confirms the diagnosis. Instead, doctors look for at least two out of three key signs: elevated male-type hormones, irregular or absent ovulation, and polycystic-appearing ovaries. The process also involves ruling out other conditions that can look similar.
The Three Criteria Doctors Look For
PCOS is diagnosed using what’s known as the Rotterdam criteria. You need to meet at least two of these three:
- High androgen levels. This means elevated “male-type” hormones like testosterone, detected either through blood tests or visible signs like excess hair growth and acne.
- Irregular ovulation. Cycles that are consistently longer than 35 days, shorter than 21 days, or absent altogether suggest you’re not ovulating regularly.
- Polycystic ovary morphology. This is identified either on ultrasound or through an elevated AMH blood level (more on both below).
If you already have irregular cycles and clear signs of high androgens, an ultrasound isn’t even necessary. Those two criteria alone are enough for a diagnosis, according to the 2023 international guidelines.
What Blood Tests Are Involved
Blood work is the backbone of PCOS testing. Your doctor will likely order several hormone levels at once. The most common panel includes total and free testosterone, a hormone called DHEAS (produced by the adrenal glands), LH, FSH, prolactin, and progesterone. Some providers also check androstenedione, another androgen.
In PCOS, the pattern that often shows up is an LH level that’s two to three times higher than FSH. Normally those two hormones sit at roughly equal levels, both in the 5 to 20 range. A woman with PCOS might have an LH of 18 and an FSH of 6, for example. Total testosterone above 40, DHEAS above 200, or that skewed LH-to-FSH ratio are all flags worth investigating further.
Progesterone is sometimes checked about a week after expected ovulation to confirm whether ovulation actually happened. A level above 14 ng/ml generally means it did. Estrogen levels, surprisingly, are usually normal in women with PCOS.
When to Time Your Blood Draw
If you’re still getting periods, blood should be drawn on days 1 through 5 of your cycle (day 1 being the first day of your period). Testosterone levels can rise misleadingly later in the cycle, which could skew results. If you’re not getting periods at all, blood can be drawn at any time.
Ultrasound and AMH Testing
A transvaginal ultrasound is one way to check whether your ovaries have the characteristic appearance of PCOS. The current threshold is at least 25 small follicles (each 2 to 9 mm in diameter) across the whole ovary, or an ovarian volume of 10 ml or greater. These follicles aren’t cysts in the traditional sense. They’re small, immature egg sacs that haven’t developed fully due to hormonal imbalance.
As of the 2023 international guidelines, a blood test measuring AMH can now be used as an alternative to ultrasound in adults. AMH is a hormone produced by those small follicles, so high levels reflect the same ovarian pattern that ultrasound would show. This is especially useful for people who can’t easily access ultrasound or prefer a simple blood draw. The guidelines are clear, though, that you should get one or the other, not both, to avoid overdiagnosis. AMH also should not be used as a standalone test for PCOS, and it’s not yet recommended for adolescents.
Tests That Rule Out Other Conditions
PCOS is partly a diagnosis of exclusion. Several other conditions cause irregular periods or elevated androgens, and your doctor needs to check for those before confirming PCOS. The standard rule-outs include:
- Thyroid dysfunction, checked with a TSH blood test. Normal is roughly 0.4 to 3.8. An underactive thyroid can cause irregular cycles and weight gain that mimic PCOS.
- High prolactin levels. Prolactin is usually under 25 ng/ml. Elevated levels can disrupt ovulation and may point to a pituitary issue rather than PCOS. Some women with PCOS do have mildly elevated prolactin in the 25 to 40 range, which can complicate the picture.
- Non-classical congenital adrenal hyperplasia, a genetic condition where the adrenal glands overproduce androgens. This is typically screened with a morning blood test measuring a specific adrenal hormone precursor.
- Pregnancy, which is a simple but important thing to rule out when periods are absent.
If you don’t have physical findings that suggest these conditions, some providers may skip certain tests. But most will run at least TSH and prolactin as part of a thorough workup.
The Physical Exam
Your doctor will also look for visible signs of excess androgens. The main ones are hirsutism (coarse hair on the face, chest, back, or abdomen), acne along the jawline and chin, and thinning hair on the scalp. Hirsutism is assessed by looking at hair growth across several body areas and scoring its severity. A score above a certain threshold counts as clinical evidence of high androgens, even if your blood testosterone comes back in the normal range.
Other things your provider may check include skin darkening in the folds of the neck, armpits, or groin (a sign of insulin resistance), your BMI, and your waist circumference. These don’t diagnose PCOS directly but help paint the full metabolic picture.
Metabolic Screening During Diagnosis
PCOS increases the risk of insulin resistance and type 2 diabetes, so most providers will screen your blood sugar as part of the initial workup. If your BMI is above 30 or you have a family history of diabetes, a fasting or random glucose test is typically included. Some doctors order a full oral glucose tolerance test, where you drink a sugary solution and have your blood drawn at intervals to see how your body handles sugar. This catches insulin resistance that a simple fasting glucose might miss.
Lipid panels (cholesterol and triglycerides) are also commonly checked, since PCOS raises cardiovascular risk over time. These metabolic tests won’t determine whether you have PCOS, but they guide what kind of management you’ll need going forward.
What the Process Looks Like in Practice
For most people, the diagnostic process takes one to two appointments. At the first visit, your doctor will ask about your cycle history, symptoms, and family history, then do a physical exam. Blood work is either drawn that day or scheduled for the right point in your cycle. If an ultrasound or AMH test is needed, that may happen at the same visit or be ordered separately.
Results usually come back within a few days to a week. If two of the three Rotterdam criteria are met and other conditions have been ruled out, you’ll get a diagnosis. Some people get a clear answer quickly. Others, especially those whose hormone levels fall in borderline ranges or who have regular cycles with only mild symptoms, may need repeat testing or a referral to an endocrinologist or reproductive specialist for a closer look.