Imagine going to the mechanic because your car keeps stalling. They check the fuel level, tell you it’s fine, and send you home. You come back two months later, same problem. This time they check the oil. Also fine. You leave again, still stalling.
Nobody checked the fuel injector. Nobody checked the spark plugs. They were only testing what was easy to test.
That’s what happens to a lot of women with PMOS. The basic tests come back “normal.” But “normal by general population standards” and “normal for someone with PMOS” are two very different things.
The 40% problem
Here’s a number that should make you pause: when women with PMOS are screened using just a fasting blood sugar test - the most common first line check for diabetes risk - it misses 40% of glucose disorders, including all cases of early diabetes.
The test most doctors reach for first is the one that’s least useful in PMOS. Why? Because insulin resistance in PMOS is a slow burn. Your blood sugar looks fine for years while your pancreas quietly works overtime to keep it that way. By the time fasting glucose rises, you’ve already had high insulin for a long time.
Fasting glucose vs. the full picture
14%
Caught by fasting glucose alone
The standard first-line test misses the vast majority of glucose problems in women with PMOS
24.5%
Caught by 2-hour OGTT
The full oral glucose tolerance test catches nearly double the cases - and finds all the diabetes ones fasting glucose misses
Source: PubMed - PCOS: OGTT vs Fasting Glucose (2019)
“Relying on fasting glucose alone is not adequate for screening in women with PMOS - regardless of age, weight, or androgen levels.”
This is why the test list for PMOS is longer and more specific than a standard annual blood panel. It’s not about being extra - it’s about actually catching what’s there. Here’s how to think about it, organised by what each tier is trying to answer.
The 4 tiers of PMOS testing
From confirmation to long-term care
Free & Total Testosterone
The primary androgen check. Free testosterone is often more informative than total. Use LC-MS assay - standard immunoassays are less accurate at female ranges.
SHBG (Sex Hormone-Binding Globulin)
A carrier protein that “mops up” testosterone. Low SHBG means more active testosterone circulating, even if your total testosterone looks normal. Also a marker of insulin resistance.
DHEA-S & Androstenedione
Two more androgens. Help identify whether the excess is coming from the ovaries or the adrenal glands - which points treatment in different directions.
DHEA-S >700 mcg/dL raises concern for a tumour - requires urgent further workup
LH & FSH (with LH:FSH ratio)
The pituitary signals that tell the ovaries what to do. In PMOS, LH is often higher than FSH - a ratio above 2:1 supports the diagnosis. Not diagnostic alone, but part of the picture.
AMH (Anti-Müllerian Hormone)
Produced by small follicles - typically 2–4x higher than normal in PMOS. As of 2023, AMH is now an official alternative to ultrasound for assessing polycystic ovarian morphology. One blood test instead of an internal scan.
Not reliable within 8 years of first period - avoid in adolescents
Transvaginal Ultrasound (if needed)
Checks for ≥20 follicles of 2–9mm in at least one ovary. Required for only about 30% of women - those with androgens but no cycle irregularity, or cycles but no androgen signs.
TSH (Thyroid Stimulating Hormone)
Thyroid problems cause irregular periods, weight changes, hair loss, fatigue - identical to PMOS. Rules out thyroid disease. Always done first. If abnormal, treat thyroid before diagnosing PMOS.
Prolactin
Elevated prolactin suppresses ovulation and mildly raises androgens - mimicking PMOS closely. Often caused by a tiny, benign pituitary adenoma. Draw fasting, in the morning.
17-Hydroxyprogesterone (17-OHP)
Rules out Non-Classical Congenital Adrenal Hyperplasia (NCAH) - an inherited enzyme deficiency that causes adrenal androgen excess. Affects about 1–5% of women suspected to have PMOS and is clinically indistinguishable without this test.
Draw in early follicular phase (days 1–5). Below 200 ng/dL usually clears it. If borderline, a Synacthen stimulation test follows.
hCG (Pregnancy test)
Always, and always first. Pregnancy causes all of the same signs - missed periods, hormonal changes, fatigue. This is step one before any other test is interpreted.
Fasting Insulin + Fasting Glucose → HOMA-IR
The insulin resistance calculation. HOMA-IR = (Fasting Insulin × Fasting Glucose) ÷ 405. About 50–70% of PMOS women have insulin resistance - including lean women with normal body weight.
PMOS-specific red flag: HOMA-IR >1.5. General lab “normal” ranges are not sensitive enough here.
Oral Glucose Tolerance Test (OGTT) - 2-hour with insulin
The gold standard for metabolic risk in PMOS. You drink a glucose solution; blood is drawn at intervals to see how your body responds. This catches the “fasting looks fine but insulin is working overtime” pattern that fasting glucose misses entirely.
2-hour insulin >100 μIU/mL indicates prolonged compensatory hyperinsulinemia - this pattern can persist for years before blood sugar rises.
HbA1c
Your 3-month average blood sugar. Useful as a baseline and for tracking, but less sensitive than OGTT for catching early insulin problems. In women with iron deficiency or thalassaemia (common in South Asian women), HbA1c can read falsely low - use OGTT instead.
Full Lipid Panel
Total cholesterol, LDL, HDL, and triglycerides. Women with PMOS have double the risk of type 2 diabetes and significantly elevated cardiovascular risk over time. The classic PMOS lipid pattern: elevated triglycerides, low HDL.
TG:HDL ratio >3 is an additional signal of insulin resistance. Repeat every 2–3 years.
Mid-Luteal Progesterone (Day 19–21)
Confirms whether you’re actually ovulating. Progesterone >3 ng/mL mid-cycle = ovulation confirmed. Useful when cycle irregularity is the main symptom.
Comprehensive Metabolic Panel (CMP)
Liver and kidney function, electrolytes. PMOS is linked to non-alcoholic fatty liver disease (NAFLD). ALT and AST in particular signal hepatic involvement from long-standing insulin resistance.
Vitamin D
Deficiency is extremely common in PMOS and worsens insulin sensitivity. Especially relevant for Indian and South Asian women, where deficiency rates are high. Worth checking and supplementing if low.
Ferritin + Iron Studies
Irregular or heavy periods cause iron deficiency over time. Also affects HbA1c accuracy. Worth checking alongside the metabolic workup.
Sources: Labcorp PCOS Diagnostic Profile · JCEM Diagnostic Challenges in PCOS, 2025 · Oana Health - IR Thresholds in PCOS
A note on timing
Most reproductive hormones (LH, FSH, estradiol, progesterone) should be drawn on cycle days 2–5 for the most accurate reading. If your periods are very irregular or absent, blood can usually be drawn any day - your doctor will advise.
When to draw what
Test timing guide
Days 2–5 (early follicular)
LH, FSH, Estradiol, 17-OHP, AMH, Total & Free Testosterone, SHBG, DHEA-S, Androstenedione
Days 19–21 (mid-luteal)
Progesterone (to confirm ovulation)
Fasting, any day
Insulin, glucose, OGTT, HbA1c, lipid panel, CMP, Vitamin D, Ferritin
Morning, fasting
Prolactin (stress, eating & exercise can temporarily raise it)
On hormonal contraception? The pill, patch, or hormonal IUD significantly alters testosterone, SHBG, LH, and FSH - making many of these tests harder to interpret. Your doctor may recommend testing off contraception, but never stop medication without guidance. Timing and interpretation can still be done with the right context.
What to bring to your appointment
The most practical thing you can do is go in with a specific list. Most of these tests can be ordered as a single morning blood draw. If your doctor isn’t familiar with PMOS-specific testing thresholds - particularly for HOMA-IR and the OGTT - that’s a sign that a specialist second opinion would be worth it.
The second opinion question: If you’ve been told “your labs look normal” but you’re still symptomatic, it’s worth asking whether the right tests were actually run - and whether the right thresholds were used. A fasting glucose of 95 mg/dL looks “normal” on a lab report. For a woman with PMOS, it can be an early signal.
In the final part of this series, we bring it all together: which tests matter most for your specific phenotype, what to track long-term, and what ongoing care for PMOS actually looks like - now that the name finally reflects the whole picture.
Up next · Part 4 of 4
Your PMOS roadmap - from diagnosis to lifelong care
→
This article is for informational purposes only. Sources: PubMed - PCOS OGTT vs FPG (2019); Labcorp PCOS Diagnostic Profile; JCEM Diagnostic Challenges (2025); Oana Health; 2023 International Evidence-Based PCOS Guidelines; RCOG Green-top Guideline No. 33.