Understanding my PCOS / PMOS blood tests
This guide does not interpret your personal results — it explains what each marker measures, what can influence it, and why it must always be interpreted in context. Interpretation remains your doctor's role.
Category 1 — Reproductive hormones
Total and free testosterone
What it measures: the main androgen to investigate in PCOS. Total testosterone measures all circulating testosterone. Free testosterone is the biologically active fraction, more difficult to measure directly.
What can influence it: time of day of the blood draw (higher in the morning), cycle phase, pregnancy, certain contraceptives, BMI, stress, laboratory method.
Interpret in context: a value within the laboratory's reference range does not rule out clinical androgen excess (hirsutism, acne) if SHBG is low. Total testosterone alone is insufficient.
SHBG (Sex Hormone Binding Globulin)
What it measures: a protein that transports sex hormones. A low SHBG increases the free fraction of testosterone — and therefore its biological activity — even if total testosterone appears normal.
What can influence it: hyperinsulinaemia (SHBG falls when insulin is high), obesity, hypothyroidism, exogenous androgens, certain contraceptives (combined oral contraceptives often increase SHBG).
Interpret as: often measured alongside testosterone to calculate the free androgen index (FAI).
DHEAS (dehydroepiandrosterone sulphate)
What it measures: an androgen produced mainly by the adrenal glands (approximately 90%). An isolated elevation of DHEAS points more toward an adrenal rather than ovarian source of androgens.
What can influence it: stress, intense physical activity, smoking, certain medications. Decreases naturally with age.
Interpret as: most useful for identifying the origin of androgens when testosterone is elevated.
Androstenedione
What it measures: a precursor of testosterone, produced by the ovaries and adrenal glands. Its measurement completes the androgenic profile when the initial workup is inconclusive.
What can influence it: cycle phase, time of blood draw, stress. Can be elevated in PCOS even when testosterone is normal.
LH and FSH
What they measure: gonadotrophins that regulate the ovarian cycle. FSH stimulates follicular development; LH triggers ovulation. In PCOS, the LH/FSH ratio is often elevated, but this is no longer a formal diagnostic criterion.
What can influence them: cycle phase (which is why testing is done on D2–D5), excess weight, stress, hormonal contraceptives (which suppress LH and FSH).
Interpret as: most useful for fertility workup or evaluating hypothalamic ovarian insufficiency.
AMH (anti-Müllerian hormone)
What it measures: produced by small developing follicles. Reflects ovarian reserve. Often elevated in PCOS due to the large number of antral follicles. Can replace ultrasound for the morphological criterion in some protocols.
What can influence it: age (decreases over time), hormonal contraceptives (can reduce AMH by 20–50%), assay method (kits are not standardised — cross-laboratory comparison is difficult).
Interpret as: a high AMH does not mean infertility. It indicates an abundant reserve. The question in PCOS is ovulation (its presence or absence), not egg quantity.
Oestradiol
What it measures: the main oestrogen, produced by the dominant follicle. Measured in the follicular phase to assess baseline ovarian activity.
What can influence it: cycle phase (very high peri-ovulatory peak), contraceptives, stress, eating disorders.
Progesterone (mid-luteal)
What it measures: measured in the luteal phase (around day 21 in a 28-day cycle, or 7 days after presumed ovulation) to confirm that ovulation has occurred. A low level can indicate anovulation.
Interpret as: if the cycle is irregular, the timing of the test is uncertain — your doctor will adapt based on context.
Category 2 — Related hormones
TSH (thyroid-stimulating hormone)
What it measures: evaluates thyroid function. Hypothyroidism can cause irregular cycles, fatigue, weight gain and an abnormal lipid profile — symptoms that overlap with PCOS.
What can influence it: time of day (slightly higher at night), intercurrent illness, medications (lithium, iodine, etc.).
Interpret as: TSH is almost always requested as a differential diagnosis. A normal TSH does not rule out autoimmune thyroid disease — a more complete thyroid panel may be discussed depending on context.
Prolactin
What it measures: a hormone that can inhibit the hypothalamic-pituitary-ovarian axis and cause absent or irregular cycles. Elevated prolactin can mimic PCOS.
What can influence it: stress at the time of the blood draw (a single stressful blood draw can falsely elevate prolactin), recent sexual activity, breastfeeding, certain medications (antipsychotics, metoclopramide). If elevated, a second measurement at rest is often recommended.
17-OH-progesterone
What it measures: screens for non-classic congenital adrenal hyperplasia (CAH), particularly 21-hydroxylase deficiency. This mild form can present like PCOS (hirsutism, irregular cycles, sometimes acne).
What can influence it: cycle phase (values higher in the luteal phase), time of day (higher in the morning fasting, which is the recommended time). Ideally measured on D2–D5.
Category 3 — Metabolic markers
Fasting glucose
What it measures: evaluates glucose tolerance. In PCOS, the risk of type 2 diabetes is 3 to 5 times higher. Fasting glucose is the first-line screen.
What can influence it: recent food intake (hence the fasting requirement), acute stress, corticosteroids, certain medications. Can vary from day to day — a single value is not definitive.
Indicative thresholds (WHO): < 5.6 mmol/L (100 mg/dL) normal; 5.6–6.9 mmol/L (100–125 mg/dL) impaired fasting glucose (pre-diabetes); ≥ 7.0 mmol/L (126 mg/dL) to be confirmed by a second test or HbA1c.
HbA1c (glycated haemoglobin)
What it measures: reflects average blood glucose over the past 3 months. More stable than a single glucose reading; not affected by fasting or the day's meal.
What can influence it: red blood cell disorders (anaemia, sickle cell disease) that can skew results. Pregnancy can also affect interpretation.
Fasting insulin
What it measures: combined with glucose, allows calculation of HOMA-IR and indirect assessment of insulin resistance. Not routinely prescribed in all clinical contexts.
What can influence it: recent food intake (hence fasting), assay method (highly variable between laboratories — one of the limitations of HOMA-IR).
HOMA-IR
What it measures: an index calculated from fasting glucose and fasting insulin to estimate insulin resistance. Formula: (glucose mmol/L × insulin µU/mL) / 22.5. You can calculate your score with our cautious tool.
Its limitations: thresholds vary by laboratory, insulin assay method, and country. A score around 1.0 is often cited as a reference in adults without diabetes; above 2.5–3.0 insulin resistance is often flagged — but these thresholds are not universal. Never interpret this score in isolation.
Lipid panel
What it measures: evaluates cardiovascular risk. The most common lipid profile in PCOS: elevated LDL and triglycerides, low HDL. These abnormalities are often linked to insulin resistance.
What can influence it: recent food intake (hence fasting), medications (combined oral contraceptives can modify the lipid profile), physical activity, smoking.
The four values to know: total cholesterol (TC), LDL cholesterol (the “bad”), HDL cholesterol (the “good” — cardiovascular protection), and triglycerides.
How do I bring these results to my doctor?
A structured summary — with the date of the blood draw, the day of your cycle, your current treatments and your questions — helps your doctor quickly contextualise your results.
Prepare my appointmentFrequently asked questions
Why is the timing in my cycle so important for hormone tests?
Reproductive hormones fluctuate enormously throughout the menstrual cycle. LH, FSH and oestradiol peak around ovulation and reach their lowest point at the start of the cycle. To compare results against reference ranges, tests are done at standardised times — generally between D2 and D5 for baseline values. Outside these windows, values are difficult to interpret.
Do I need to fast for all hormone tests?
No. Fasting glucose, insulin, lipid panel, and often testosterone require an 8–12 hour fast. TSH, AMH, prolactin and 17-OH-progesterone can generally be done without strict fasting, depending on local protocols. Your laboratory will specify the conditions.
What is a "normal" result for these markers?
There is no universal normal value. Each laboratory defines its own reference intervals based on its assay method, the population studied, and the kits used. A value 'outside the normal range' should always be read with the laboratory's own reference intervals, and interpreted in clinical context by your doctor.
My AMH is high — does that mean I am infertile?
No. A high AMH reflects a large number of follicles in reserve — which is common in PCOS. A high ovarian reserve does not mean infertility: the problem in PCOS is often the absence or rarity of ovulation (anovulation), not a lack of eggs. A high AMH can even be a favourable factor in some IVF protocols. Your doctor will contextualise this result within your overall workup.
Should I redo tests if thresholds vary between laboratories?
If there is doubt about interpreting a result, it can be useful to repeat the test at the same laboratory for comparable values (same method, same reference intervals). Changing laboratories mid-follow-up can introduce variations that have no real clinical significance. Let your doctor know if you change laboratories.
How do I prepare to bring my results to my doctor?
Always bring your results — paper or digital — with the laboratory's reference intervals, the date of the blood draw, and the day of your cycle if you know it. To organise this information in a structured way, you can use our appointment preparation tool.
Main sources
- NIH / NICHD — PCOS information (hormonal and metabolic aspects)
- NHS — Polycystic ovary syndrome (PCOS)
- International Evidence-based Guideline 2023 (Monash) — diagnostic markers
- Mayo Clinic — PCOS: biology and imaging
Page written from official public sources. It does not constitute an interpretation of your personal results. For any questions about your workup, consult your doctor.