Guide
How PCOS Is Diagnosed: Criteria, Blood Tests, and What to Ask Your Doctor
Adults are diagnosed with PCOS when they meet 2 of 3 criteria after other causes are ruled out. Here is how the criteria work, which blood tests and scans are used and why, and questions to bring to your appointment.
By PCOS Polly ·
Key takeaways
- Adults need 2 of 3 features: irregular ovulation, signs of high androgens, and polycystic ovaries on ultrasound or a high AMH level.
- If you have irregular cycles plus clear androgen signs, an ultrasound is often not needed.
- Teens need both irregular cycles and androgen signs; ultrasound and AMH are not used to diagnose PCOS in teens.
- There is no single PCOS blood test: clinicians combine hormone labs, rule-out tests (TSH, prolactin, 17-OHP, pregnancy), and metabolic screening.
- The 2023 guideline recommends checking glucose, ideally with a 75 g oral glucose tolerance test, because PCOS raises diabetes risk.
Adults are diagnosed with PCOS when they meet 2 of 3 criteria (irregular ovulation, signs of high androgens, and polycystic ovaries on ultrasound or a high AMH level) after look-alike conditions are ruled out. Teens need both irregular cycles and androgen signs; ultrasound and AMH are not used to diagnose teens. There is no single PCOS blood test. Clinicians combine hormone labs, rule-out tests, and metabolic screening, and if you already have irregular cycles plus clear androgen signs, you may not need an ultrasound at all.
The three diagnostic criteria
| Criterion | What counts | Notes |
|---|---|---|
| 1. Irregular ovulation | Cycles shorter than 21 or longer than 35 days, or fewer than 8 periods a year | Age-adjusted definitions apply for teens |
| 2. High androgens | Clinical signs (acne, hirsutism, scalp thinning) and/or high total or free testosterone on a blood test | LC-MS/MS testosterone assays are preferred |
| 3. Polycystic ovary morphology | Follicle-count thresholds on ultrasound in adults, or an elevated AMH level | AMH as an alternative to ultrasound was added in 2023; not used in teens |
Shortcut: irregular cycles plus clear androgen signs meet the definition, so the diagnosis can stop there.
What gets ruled out first
| Test | Why it is ordered |
|---|---|
| TSH | Thyroid problems can mimic irregular cycles |
| Prolactin | High prolactin causes irregular or missing periods |
| 17-hydroxyprogesterone (17-OHP) | Screens for non-classic congenital adrenal hyperplasia when indicated |
| hCG (pregnancy test) | If periods have stopped |
| CBC and other tests | For heavy bleeding, as needed |
Rare androgen-secreting tumors are considered when symptoms start suddenly or are severe.
Hormone tests and what they answer
| Test | In plain English |
|---|---|
| Total testosterone (LC-MS/MS preferred) | Are androgens elevated? |
| Free testosterone or free androgen index | How much androgen is unbound and active; often more informative than total alone |
| Androstenedione and DHEA-S | Other androgen sources if testosterone is not high; DHEA-S reflects the adrenal glands |
| AMH | Reflects the number of small follicles; can replace ultrasound for the ovary criterion in adults, not teens |
| LH and FSH | Context for ovulation signaling; the LH:FSH ratio is not a diagnosis |
| Estradiol and progesterone | Cycle timing; a mid-luteal progesterone can confirm ovulation happened |
Timing tip: androgen labs are easier to interpret after a stretch off hormonal birth control when the diagnosis is still open. Ask before you stop anything. See post-pill PCOS for what to expect.
Metabolic screening most people with PCOS need
| Test | In plain English |
|---|---|
| Fasting glucose or A1c | Screens for prediabetes and diabetes |
| 75 g oral glucose tolerance test (OGTT) | Recommended by the 2023 guideline as the most accurate glucose test in PCOS; catches problems fasting tests miss |
| Fasting insulin or HOMA-IR | Sometimes ordered; a useful trend tool, but without a standardized diagnostic cutoff |
| Lipid panel | Heart and metabolic risk |
| ALT and AST | Liver health, especially with metabolic risk factors |
Learn what those results mean in PCOS and insulin resistance.
What a good diagnostic visit includes
- History: your cycle calendar, acne and hair timeline, weight and energy changes, medications, and family history of diabetes or PCOS
- Exam: skin, hair pattern, and blood pressure
- Labs tailored to you, not a random 20-test panel
- Ultrasound only when the third criterion is still needed or bleeding needs another explanation
Questions worth asking
- “Do I meet 2 of 3 criteria, and which ones?”
- “Which of these labs are for diagnosis and which are for long-term risk?”
- “Can my testosterone be run by LC-MS/MS?”
- “Do I need an ultrasound, or is AMH an option?”
- “Should we screen glucose with an OGTT, an A1c, or both?”
- “What is the plan if I go more than 3 months without a bleed?”
- “What are my options for my top goal: skin, cycles, fertility, or blood sugar?”
What to bring
Period dates for the last 6-12 months, photos of acne or hair changes if helpful, your supplement and medication list, and your number-one goal for the next 3 months. If you are not sure your symptoms add up, start with our PCOS symptoms checklist.
Keep your timeline in PCOS Polly
PCOS Polly turns messy cycle memory into a shareable timeline, and lets you store lab dates and result notes next to your symptoms so trends are obvious at follow-up. More guides live on the PCOS Polly blog, including what is PCOS.
Sources
- Teede HJ et al. 2023 International Evidence-based Guideline for the Assessment and Management of PCOS.
- Cleveland Clinic. Polycystic ovary syndrome (PCOS).
- Mayo Clinic. PCOS: diagnosis and treatment.
This article is for general wellness information and is not medical advice. Only a qualified clinician can diagnose PCOS or interpret your test results.
Frequently asked questions
How is PCOS diagnosed? +
Under the 2023 International PCOS Guideline, adults are diagnosed when they have two of three features: irregular or absent ovulation, clinical or biochemical signs of high androgens, and polycystic ovary morphology on ultrasound or an elevated AMH level. Other conditions with similar symptoms must be ruled out first.
What blood tests are used to check for PCOS? +
Common tests include total and free testosterone, sometimes DHEA-S and androstenedione, plus TSH, prolactin, and 17-hydroxyprogesterone to rule out look-alikes, and a pregnancy test if periods have stopped. Metabolic screening usually includes glucose or A1c, often an oral glucose tolerance test, and a lipid panel.
Do you need an ultrasound to diagnose PCOS? +
Not always. If you have irregular cycles and clear signs of high androgens, you already meet two criteria and an ultrasound is not required. In adults, an AMH blood test can also be used instead of ultrasound for the ovary criterion.
Is the LH to FSH ratio used to diagnose PCOS? +
No. A high LH to FSH ratio is common in PCOS, but the 2023 guideline does not use it as a diagnostic test because many people with PCOS have a normal ratio.
Can PCOS be diagnosed while on birth control? +
Hormonal birth control changes androgen levels and masks cycle patterns, which makes diagnosis harder. Clinicians often prefer to assess after a stretch off hormonal contraception when the diagnosis is still open. Do not stop any medication without talking to your doctor first.
Can a normal ultrasound rule out PCOS? +
No. You can be diagnosed without polycystic-appearing ovaries if you have both irregular ovulation and signs of high androgens. And polycystic-appearing ovaries alone, without other features, do not mean you have PCOS.
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