PCOS is a hormonal condition driven by metabolic dysfunction. Most blood tests check the hormones and ignore the metabolism. That is like treating the symptom and missing the engine. Here is what a proper PCOS blood test should actually include.
A typical GP PCOS workup checks testosterone, LH, FSH, and maybe thyroid (TSH only). If testosterone is elevated and LH is high relative to FSH, you get a PCOS label. You might be prescribed the contraceptive pill to "manage" it. Nobody tests your insulin.
This matters because insulin resistance drives PCOS in up to 70% of cases. Elevated insulin stimulates the ovaries to produce excess androgens. It lowers SHBG, increasing free testosterone. It promotes weight gain, which worsens insulin resistance, which worsens the PCOS. It is a self-reinforcing cycle, and the standard PCOS blood test does not even look at it.
Total testosterone alone is not enough. SHBG determines how much is bioavailable. A "normal" total testosterone with low SHBG means high free testosterone and androgenic symptoms (acne, excess hair growth, hair thinning). The free androgen index, calculated from testosterone and SHBG, is the most clinically useful measure. Low SHBG itself is often a sign of insulin resistance.
In classic PCOS, LH is elevated relative to FSH, typically with an LH:FSH ratio above 2:1. This drives excess ovarian androgen production and disrupts ovulation. But not all PCOS presents this way. Some women have normal LH:FSH ratios and insulin-driven androgen excess instead. Testing both pathways reveals which type of PCOS you have, which determines the treatment approach.
This is the most important test the NHS does not do for PCOS. Fasting insulin reveals whether your pancreas is overworking to keep glucose normal. HOMA-IR quantifies the degree of insulin resistance. If your HOMA-IR is above 2.0, insulin resistance is likely driving your PCOS. The treatment shifts from symptom management (the pill) to root cause intervention (diet, exercise, possibly metformin or inositol). Without testing insulin, you will never know which approach is right for you. Metabolic testing guide.
Not all excess androgens come from the ovaries. DHEA-S is produced by the adrenal glands, and elevated DHEA-S with normal ovarian androgens points to adrenal-driven androgen excess rather than classic ovarian PCOS. The treatment approach is different. Stress management and cortisol regulation become the priority rather than ovarian suppression with the pill.
Hypothyroidism causes irregular periods, weight gain, fatigue, and hair changes that mimic PCOS. It also raises SHBG and alters androgen metabolism. Full thyroid testing (TSH, Free T3, Free T4, antibodies) rules out thyroid dysfunction as a contributing factor or alternative diagnosis. If both PCOS and thyroid dysfunction are present, treating the thyroid first often improves the PCOS picture. Thyroid testing guide.
Elevated prolactin can cause irregular periods and mimic PCOS. It can also indicate a pituitary adenoma. Prolactin should be part of every PCOS workup to rule out this alternative diagnosis. Most GPs and private providers do not include it.
Chronic stress elevates cortisol, which drives insulin resistance, raises blood sugar, promotes visceral fat storage, and disrupts the menstrual cycle independently of PCOS. High cortisol alongside elevated DHEA-S suggests adrenal-driven androgen excess. Cortisol context is essential for understanding why your other markers are what they are.
PCOS is associated with chronic low-grade inflammation, which independently worsens insulin resistance and cardiovascular risk. hs-CRP quantifies systemic inflammation. Elevated hs-CRP in PCOS is not just a marker. It is a modifiable risk factor that responds to dietary changes, omega-3 supplementation, and exercise.
PCOS is not one condition. It is a syndrome with multiple drivers. Your blood test results reveal which type you have, which determines what will actually help.
The most common type (~70%). High insulin drives excess ovarian androgens. Elevated HOMA-IR, low SHBG, high free androgen index. Treatment priority: reduce insulin resistance through diet (lower refined carbohydrates, higher protein and fibre), resistance training, sleep optimisation, and potentially inositol or metformin.
Elevated DHEA-S with normal ovarian androgens and normal insulin. The adrenal glands are the primary androgen source, often driven by chronic stress. Treatment priority: stress management, cortisol regulation, sleep, and adaptogens. The contraceptive pill suppresses ovarian androgens but does nothing for adrenal-driven excess.
Elevated hs-CRP, chronic symptoms worsened by stress and dietary triggers. Inflammation drives androgen production independently of insulin. Treatment priority: anti-inflammatory diet, gut health, omega-3 supplementation, identifying and removing dietary triggers. Often overlaps with insulin-resistant PCOS.
Symptoms emerge after stopping hormonal contraception. The pill suppressed LH and androgen production for years. Coming off it causes a temporary rebound. Hormones often normalise within 3 to 12 months without intervention. Testing confirms whether it is a transient rebound or underlying PCOS that the pill was masking.
A basic testosterone and LH test cannot distinguish between these types. A comprehensive panel that includes insulin, DHEA-S, cortisol, thyroid, and inflammatory markers can. Your TrueVitals report identifies the pattern and gives you targeted recommendations for your specific type.
PCOS is not just a reproductive condition. It carries long-term metabolic and cardiovascular risks that require ongoing monitoring.
Women with PCOS are 3 to 5 times more likely to develop type 2 diabetes. Insulin and HOMA-IR track this risk years before HbA1c becomes abnormal.
Insulin resistance, chronic inflammation, and dyslipidaemia increase cardiovascular risk. ApoB and the triglyceride/HDL ratio are the most informative tracking markers.
Irregular ovulation means the endometrium is exposed to unopposed oestrogen. Progesterone testing confirms whether ovulation is occurring. Prolonged anovulation increases endometrial cancer risk.
PCOS is associated with higher rates of anxiety and depression. Insulin resistance, inflammation, and hormonal imbalance all contribute. Testing and treating the biochemical drivers can improve mental health alongside physical symptoms.
PCOS is the most common cause of anovulatory infertility. LH, FSH, progesterone (day 21), and insulin all inform the fertility picture. Treating insulin resistance improves ovulation rates in many women without requiring medication.
NAFLD is more common in women with PCOS due to insulin resistance. ALT and GGT are the screening markers. A comprehensive panel catches liver involvement that a hormone-only test would miss.
PCOS diagnosis requires two of three Rotterdam criteria: irregular periods, hyperandrogenism (elevated testosterone/DHEA-S), and polycystic ovaries on ultrasound. Blood tests should include testosterone, SHBG, FAI, LH, FSH, DHEA-S, fasting insulin, HOMA-IR, full thyroid, prolactin, cortisol, and hs-CRP. TrueVitals Ultimate (115 biomarkers for women, £349) includes all of these.
Rarely. The NHS typically tests testosterone, LH, FSH, and sometimes thyroid (TSH only) for PCOS. Fasting insulin and HOMA-IR are not routinely tested despite insulin resistance driving PCOS in up to 70% of cases. A private comprehensive panel fills this gap. NHS vs private comparison.
Day 2 to 5 for baseline hormones (testosterone, LH, FSH, oestradiol). If your periods are irregular or absent, test any day. Progesterone on day 21 confirms ovulation if you are still having cycles. Insulin, thyroid, and inflammatory markers can be tested any day with a morning fasted draw.
PCOS cannot be "cured" but its symptoms and metabolic risks can be significantly improved. Reducing insulin resistance through diet (lower refined carbohydrates, higher protein), resistance training, sleep, and stress management improves hormone balance, restores ovulation in many women, and reduces long-term disease risk. Testing identifies which drivers to target and tracks progress.
The Ultimate panel (115 biomarkers for women, £349) covers every marker relevant to PCOS: complete hormones, insulin, HOMA-IR, full thyroid with antibodies, inflammation, cardiovascular risk, liver function, and iron studies. It reveals which type of PCOS you have and what is driving it. Compare all panels.
Insulin, testosterone, SHBG, LH/FSH, DHEA-S, cortisol, thyroid, inflammation, and 107 other markers. Find out which type of PCOS you have. £349.
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