PCOS Diagnosis Guide

Understanding PCOS Lab Results

A plain-language guide to every blood test relevant to PCOS — what each measures, what ranges mean, when to get tested, and how to use results to advocate for better care.

Last reviewed: June 25, 2025

H

HerPCOS Editorial Team

Evidence-based health content for women with PCOS

Last reviewed

June 25, 2025

Evidence-based

This content is for general informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider for diagnosis and treatment.

Why Lab Results Matter in PCOS

PCOS is a complex hormonal condition with no single definitive test. Diagnosis uses a combination of symptoms, ultrasound findings, and blood work. But lab results don't just confirm diagnosis — they guide treatment, reveal hidden metabolic risks, and track your progress over time.

The challenge is that standard laboratory reference ranges are often too broad to catch the subtle imbalances common in PCOS. A result labelled "normal" on your report may still be contributing to your symptoms. Understanding what your specific numbers mean — and what ranges to aim for — empowers you to have more productive conversations with your healthcare team.

This guide covers three categories of tests: reproductive hormones, metabolic markers, and other important labs. We also cover when in your cycle to get each test for the most accurate results.

When to Get Each Test

Hormone levels fluctuate throughout your menstrual cycle. Testing at the wrong time makes results hard to interpret. Use this timing guide when scheduling labs:

Days 2–5

LH, FSH, Estradiol, Total Testosterone, Free Testosterone, DHEAS

Day 21–23

Progesterone (confirms whether ovulation occurred)

Any time

AMH, HbA1c, Prolactin, TSH, Vitamin D, Ferritin

Fasting (any day)

Fasting Glucose, Fasting Insulin, Lipid Panel

If your cycles are irregular or absent, many labs can still be done at any time — inform your doctor and they will interpret accordingly.

Reproductive Hormone Tests

These tests evaluate the hormones directly involved in ovulation, androgens, and the PCOS diagnostic criteria. Most doctors order a subset — knowing what to ask for ensures you get a complete picture.

Total Testosterone

Why it matters: The primary androgen in PCOS. Elevated in most women with PCOS and drives symptoms like acne, hirsutism, and hair loss.
Normal rangeWomen: 15–70 ng/dL
In PCOSOften >70 ng/dL (may be mildly elevated or at high-normal)
Best timing: Days 2–5 of cycle, or any day if irregular

Free Testosterone

Why it matters: The fraction not bound to protein — the biologically active form. More sensitive than total testosterone for detecting androgen excess.
Normal range0.3–1.9 ng/dL (varies by lab)
In PCOSElevated free testosterone even with normal total is significant
Best timing: Same as total testosterone

DHEAS (Dehydroepiandrosterone Sulfate)

Why it matters: An adrenal androgen. Elevated in 20–30% of women with PCOS, pointing to adrenal involvement. Also elevated in adrenal tumours (rare).
Normal range35–430 mcg/dL (age-dependent)
In PCOSMay be elevated — adrenal contribution to androgen excess
Best timing: Any time of day

LH (Luteinizing Hormone)

Why it matters: LH triggers ovulation. In PCOS, LH is often chronically elevated, disrupting the normal LH surge needed for ovulation.
Normal rangeFollicular phase: 2–15 IU/L
In PCOSOften elevated — LH:FSH ratio >2:1 is classic PCOS finding
Best timing: Days 2–5 of cycle (follicular phase)

FSH (Follicle Stimulating Hormone)

Why it matters: FSH stimulates follicle (egg) development. Often normal or low-normal in PCOS. Used alongside LH to calculate the LH:FSH ratio.
Normal rangeFollicular phase: 3–10 IU/L
In PCOSOften normal; LH:FSH ratio > 2 suggests PCOS
Best timing: Days 2–5 of cycle

AMH (Anti-Müllerian Hormone)

Why it matters: Produced by ovarian follicles. Elevated in PCOS due to the large number of small follicles. Also a marker of ovarian reserve (egg supply).
Normal range1–3.5 ng/mL (varies by age)
In PCOSTypically >3.5–4 ng/mL; can be 2–3× higher than average
Best timing: Any time of cycle — very stable

Estradiol (E2)

Why it matters: The primary oestrogen. Helps interpret LH/FSH results. In the follicular phase, low or normal estradiol is expected; very high levels may indicate a large cyst.
Normal rangeFollicular phase: 20–150 pg/mL
In PCOSVaries — usually normal but can be elevated with large follicles
Best timing: Days 2–5 of cycle

Progesterone

Why it matters: Confirms whether ovulation occurred. A level above 3 ng/mL on Day 21–23 (or 7 days post-ovulation) indicates ovulation. Low in anovulatory cycles.
Normal rangeMid-luteal: >10 ng/mL (confirms ovulation)
In PCOSOften low (<3 ng/mL) due to infrequent ovulation
Best timing: Day 21–23 (7 days after presumed ovulation)

Metabolic & Insulin Tests

Up to 70% of women with PCOS have insulin resistance. These tests identify metabolic dysfunction that drives many PCOS symptoms and long-term health risks. Many are not automatically ordered — you may need to ask.

Fasting Glucose

Why it matters: Screens for prediabetes and diabetes. High glucose indicates poor insulin response. Women with PCOS have 5–10× higher risk of developing type 2 diabetes.
Normal / Target70–99 mg/dL (normal), 100–125 (prediabetes)
In PCOSEven 'normal' levels in the 90–99 range deserve attention in PCOS
Timing: After 8–12 hours fasting

Fasting Insulin

Why it matters: The most sensitive test for insulin resistance in PCOS. Can be high even with normal glucose — glucose stays normal initially because more insulin is produced to compensate.
Normal / Target2–20 mIU/L (ideally below 10)
In PCOSOften elevated (>15–20 mIU/L); >25 suggests significant resistance
Timing: After 8–12 hours fasting

HbA1c (Glycated Haemoglobin)

Why it matters: Reflects average blood sugar over the past 3 months. Useful for longer-term metabolic tracking and detecting prediabetes before fasting glucose becomes abnormal.
Normal / TargetBelow 5.7% (normal), 5.7–6.4% (prediabetes)
In PCOSAim for below 5.5% in PCOS for optimal metabolic health
Timing: Any time — no fasting required

HOMA-IR (Calculated)

Why it matters: A calculated measure of insulin resistance using fasting glucose and fasting insulin. Not a direct blood test — your doctor calculates it. Score above 2.0–2.5 suggests insulin resistance.
Normal / TargetHOMA-IR < 2.0
In PCOSFormula: (fasting insulin × fasting glucose) ÷ 405
Timing: Calculated from fasting labs

Lipid Panel

Why it matters: PCOS is associated with dyslipidaemia: high triglycerides, low HDL ('good' cholesterol), and elevated small dense LDL. This raises cardiovascular risk.
Normal / TargetTG <150, LDL <100, HDL >60 mg/dL (general targets)
In PCOSOften shows high TG, low HDL — metabolic syndrome pattern
Timing: Fasting for most accurate TG measurement

Other Important Tests

These tests rule out conditions that can mimic PCOS and identify treatable nutrient deficiencies that worsen symptoms.

TSH (Thyroid Stimulating Hormone)

Thyroid disorders are more common in women with PCOS and can cause symptoms that overlap or worsen PCOS. Hypothyroidism causes irregular periods, weight gain, fatigue, and hair loss — all symptoms that can be misattributed to PCOS.

Target: 0.4–4.0 mIU/L (optimal for PCOS: 1–2 mIU/L)
Timing: Any time of day

Ferritin (Iron Stores)

Low ferritin is the most common nutritional deficiency in women with PCOS, particularly those with heavy periods. Low ferritin causes fatigue and hair shedding even without full anaemia.

Target: 12–150 ng/mL (aim for >70 for hair health)
Timing: Any time; repeat with iron panel if low

Vitamin D

Deficiency is extremely common in PCOS and is linked to worse insulin resistance, mood, and fertility outcomes. Supplementation may improve insulin sensitivity.

Target: 30–100 ng/mL (aim for 50–70 in PCOS)
Timing: Any time

Prolactin

Elevated prolactin can cause irregular periods and mimic PCOS symptoms. Should be checked at initial PCOS workup to rule out a pituitary adenoma as an alternative cause.

Target: 3–30 ng/mL
Timing: Morning, ideally at rest; stress can elevate it acutely

Frequently Asked Questions

What blood tests should I ask for if I think I have PCOS?+
Ask your doctor for: LH, FSH, total and free testosterone, DHEAS, AMH, estradiol (day 2–5), fasting glucose and insulin, HbA1c, TSH, prolactin, ferritin, and vitamin D. Also request a pelvic ultrasound for ovarian morphology. Not every lab in the list is essential — your doctor will prioritise based on your symptoms.
My testosterone is 'normal' but I have PCOS symptoms. Is that possible?+
Yes — many women with PCOS have androgens in the 'normal' female range but still have symptoms. This can happen when free testosterone is elevated even with normal total levels, when your follicles are more sensitive to normal androgen levels (genetic), or when elevated insulin is driving symptoms through non-androgen pathways. Always request free testosterone alongside total.
When should I get my hormone labs done in my cycle?+
Key hormone tests (LH, FSH, estradiol, testosterone) are best done on Days 2–5 of your menstrual cycle when they're most interpretable. If your cycles are very irregular or you don't have periods, you can get them done at any time — let your doctor know and they'll interpret accordingly. AMH, TSH, and metabolic labs can be done any time.
What is AMH and what does it tell me about PCOS?+
AMH (Anti-Müllerian Hormone) is produced by your ovarian follicles. In PCOS, the large number of small, arrested follicles causes AMH to be 2–3× higher than average. AMH also reflects ovarian reserve (how many eggs you have remaining). A very high AMH isn't a sign of better fertility in PCOS — it means many follicles aren't maturing to the point of ovulation.
My doctor says my labs are 'normal' but I still feel unwell. What should I do?+
Standard reference ranges are based on population averages and don't account for PCOS-specific optimal ranges. For example, fasting insulin of 18 mIU/L is technically within 'normal' range but suggests significant insulin resistance in a PCOS context. Ask specifically for fasting insulin (often not part of standard panels), free testosterone, and AMH — these are routinely omitted from basic screens. Consider seeing an endocrinologist who specialises in PCOS.
Do I need to fast before my hormone blood tests?+
Fasting is required for fasting glucose, fasting insulin, and lipid panels. Hormone tests (LH, FSH, AMH, testosterone) don't require fasting but are cycle-day dependent. TSH, vitamin D, ferritin, and prolactin can be done any time without fasting. When in doubt, fast overnight (8–12 hours) before your early-morning test appointment — it won't affect hormone results and gives you flexibility.

Medical References

  1. [1]Azziz R, et al. (2009). The Androgen Excess and PCOS Society criteria for the polycystic ovary syndrome. Fertil Steril. 91(2):456–488.
  2. [2]Dunaif A. (1997). Insulin resistance and the polycystic ovary syndrome: mechanism and implications for pathogenesis. Endocr Rev. 18(6):774–800.
  3. [3]Teede HJ, et al. (2018). International evidence-based guideline for the assessment and management of polycystic ovary syndrome. Hum Reprod. 33(9):1602–1618.
  4. [4]Pigny P, et al. (2016). Elevated serum level of anti-Mullerian hormone in patients with polycystic ovary syndrome. J Clin Endocrinol Metab. 88(12):5957–5962.
  5. [5]Escobar-Morreale HF. (2018). Polycystic ovary syndrome: definition, aetiology, diagnosis and treatment. Nat Rev Endocrinol. 14(5):270–284.

Reference ranges and interpretations in this guide are based on published medical literature. Individual labs may use slightly different reference ranges. Always discuss your specific results with your healthcare provider.

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