PCOS and Blood Tests: What Hormonal Imbalances to Look For

Quick answer

Doctors diagnose PCOS using 2 of 3 signs. These signs are called the Rotterdam criteria. They are irregular ovulation, signs of extra male-type hormones, and polycystic ovaries on ultrasound. Blood tests often show a high LH to FSH ratio, above 2 to 1. Total or free testosterone often runs high. DHEA-S is sometimes high too. Fasting insulin and AMH are often high as well. Insulin resistance drives most cases.

What PCOS looks like

Common signs include:

• Irregular or missed periods.
• Trouble getting pregnant, or no ovulation.
• Acne and oily skin.
• Hirsutism. This means extra hair growth on the face or body.
• Thinning hair on the scalp.
• Weight gain, especially around the belly.
• Insulin resistance. Your body needs more insulin than normal to manage blood sugar.
• Sometimes dark, velvety skin patches. Doctors call this acanthosis nigricans.

Doctors look at your symptoms first. Blood tests support that diagnosis. They do not replace it.

The Rotterdam criteria

Doctors rule out other causes first. Then they check for 2 of these 3 signs:

1. Irregular ovulation. This shows up as irregular periods, or cycles with no ovulation.
2. Signs of extra male-type hormones. You may see this, like extra hair growth or acne. Or it may show up as high testosterone or DHEA-S on a blood test.
3. Polycystic ovaries on ultrasound. This means 12 or more small follicles on one ovary. Or it means a larger than normal ovary.

A woman with only one of these signs does not have PCOS. She may have a different cause instead. It could explain hair growth, irregular periods, or ovary changes on its own.

The PCOS blood test panel

Sex hormones

Doctors time these tests to day 3 of your cycle. This applies if you still get periods.

Free testosterone matters more than the total number. SHBG changes how much your body can use. A high AMH supports a PCOS diagnosis. But it is not one of the three Rotterdam signs.

Metabolic markers

These matter just as much as the hormone tests.

Insulin resistance drives most PCOS cases. Left unmanaged, it can lead toward prediabetes over time. PCOS also often raises triglycerides. It raises ApoB too. Both are heart risk markers. It can raise fatty liver risk as well.

Thyroid

TSH, Free T4, and Free T3 all matter here too. Thyroid disease can cause symptoms that look like PCOS. So doctors always rule it out.

Common PCOS patterns

Pattern 1: Classic insulin-resistant PCOS

• High fasting insulin and HOMA-IR.
• High AMH.
• High total and free testosterone.
• LH to FSH ratio above 2 to 1.
• Low SHBG.
• Often carries extra weight, especially around the belly.
• Symptoms include irregular cycles, acne, extra hair growth, and stubborn weight.

Pattern 2: Lean PCOS

• Normal weight, sometimes even underweight.
• Insulin resistance is less obvious here. But it is often still present. Fasting insulin often still runs high.
• Shows the same extra-hormone pattern as classic PCOS.
• More common in some Asian populations.

Pattern 3: Adrenal-driven PCOS

• High DHEA-S.
• Sometimes high 17-OH progesterone. Doctors must rule out congenital adrenal hyperplasia first.
• Shows extra-hormone symptoms.
• Next step: confirm CAH is ruled out. Sometimes needs a specialist hormone workup.

Pattern 4: Conditions that mimic PCOS

• Non-classical CAH causes high 17-OH progesterone. It needs different treatment than PCOS.
• Hyperprolactinemia causes high prolactin. It needs a different type of medicine.
• Thyroid disease causes abnormal TSH or T4 results.
• Cushing's syndrome causes high cortisol. It is rare, but it can look like PCOS.
• A hormone-producing tumor makes symptoms worsen fast. Testosterone also runs very high.

Each of these needs different treatment. This is why a full blood workup matters so much.

Why PCOS testing often falls short

Many standard checkups test basic hormones. This includes FSH, LH, and prolactin. But they often skip:

• Fasting insulin, the key metabolic marker.
• Free testosterone, which is more sensitive than total testosterone.
• SHBG, which helps you read the other results correctly.
• 17-OH progesterone, to rule out CAH.
• AMH, which supports the diagnosis.
• A full metabolic panel, including HbA1c, cholesterol, and ALT.

Adding these tests closes the gap. It gives you a clearer answer.

Want the complete PCOS workup in one panel? Book your &you Labs panel. It explains both your hormone and metabolic markers together.

How to manage PCOS

PCOS is a long-term condition. You manage it, rather than cure it. Here is what helps.

Lifestyle changes, the foundation

• Improve insulin sensitivity. Cut back on refined carbs and sugar. Walk after meals. Add resistance training.
• Manage your weight. Losing just 5 to 10% of your body weight often helps. It can bring back ovulation.
• Eat an anti-inflammatory diet, like a Mediterranean-style pattern.
• Sleep well. Good sleep supports insulin sensitivity.
• Manage stress.

Medicines your doctor may consider

• Metformin improves insulin sensitivity. It may bring back ovulation.
• Combined birth control pills regulate your cycle. They lower extra hormones too.
• Spironolactone is an anti-androgen medicine. Doctors use it for extra hair growth and acne.
• Letrozole or clomiphene help trigger ovulation. Doctors use these for women trying to conceive.
• GLP-1 medicines are a newer option. Semaglutide and tirzepatide help with insulin resistance and weight.
• Inositol is a natural compound. It has modest evidence for supporting ovulation.

Long-term health to watch

• Heart health monitoring.
• Diabetes screening.
• Fatty liver monitoring.
• Watching for endometrial changes. Irregular ovulation raises this risk over time.
• Fertility planning, when that matters to you.

How &you Labs handles PCOS testing

A &you Labs panel has a female hormone module. It covers day-3 FSH, LH, and estradiol. It also covers prolactin, testosterone, SHBG, DHEA-S, and AMH, timed correctly. The comprehensive panel adds metabolic markers too. This means fasting insulin, HOMA-IR, HbA1c, cholesterol, ApoB, ALT, and hs-CRP. Your report explains the pattern in plain language. A doctor adds written notes too.

Frequently asked questions

Can you have PCOS with regular periods?

Yes. Some women have polycystic ovaries on ultrasound. They also have extra hormones. But they still ovulate on a regular schedule. The Rotterdam criteria only need 2 of the 3 signs, not all three.

Can lean women have PCOS?

Yes. Doctors call this lean PCOS, and it is well known. Insulin resistance is often still present, even at a normal weight. This shows up especially often in Asian women.

Is PCOS curable?

PCOS is a long-term condition, but it responds well to treatment. Many symptoms improve a lot with weight loss, lifestyle change, and medicine. This includes insulin resistance, irregular cycles, and extra hormones. Some women see symptoms fade almost completely with steady effort.

Does PCOS cause infertility?

PCOS is a leading cause of fertility trouble. But it responds well to treatment. Ovulation-triggering medicine, metformin, and lifestyle change restore fertility for most women.

Should I get tested if I only have one symptom?

A single symptom is common. Irregular cycles or mild acne do not always mean PCOS. Testing makes sense once you notice 2 or more symptoms. It also makes sense when you are planning for pregnancy.

Key takeaways

• Doctors diagnose PCOS using 2 of 3 Rotterdam signs. Blood tests support the diagnosis, but do not make it alone.
• The PCOS blood pattern includes a high LH to FSH ratio, high free testosterone, low SHBG, high AMH, and often high fasting insulin and HOMA-IR.
• Insulin resistance drives most cases. Lean PCOS is real and common.
• Always rule out PCOS look-alikes. These include CAH, hyperprolactinemia, thyroid disease, and Cushing's syndrome.
• Treatment combines lifestyle change, metabolic medicine, hormone regulation, and fertility support when needed.