The blood markers I have tested

Testosterone, free testosterone and FAI

Women make testosterone too, in small amounts. Free testosterone and the FAI (free androgen index) show how much of it is active. The international PCOS guideline uses them to assess an excess of male hormones. In 595 healthy women, testosterone fell mostly at a younger age, and the menopause itself caused no extra drop.

Reference range: testosterone 0.48-1.85 nmol/L · FAI below 4 (women under 50; varies by lab) · GP: only with a reason

SHBG

SHBG is a protein that binds testosterone and oestrogen in your blood. Only the free part is active. In postmenopausal women, a low SHBG was linked to a much higher risk of type 2 diabetes. The pill raises SHBG, which makes hormone results hard to read while you take it.

Reference range: women 19.8-155 · men 13.5-71.4 nmol/L (varies by lab) · GP: only with a reason

DHEA-S

DHEA-S is a hormone from your adrenal glands that your body turns into testosterone, among other things. It falls with age, and the PCOS guideline calls it a less precise extra test when testosterone is normal. Across 23 studies in 1,188 postmenopausal women, extra DHEA did not clearly improve libido.

Reference range: women aged 30-39 1.6-6.2 µmol/L; falls with age (varies by lab) · GP: not standard

Cortisol (morning)

Cortisol is your main stress hormone. It peaks in the morning, and doctors use a morning level as a first check that your adrenal glands make enough of it. A review of 58 studies found no evidence for 'adrenal fatigue' caused by stress.

Reference range: before 10 am 101-536 nmol/L (varies by lab) · GP: only with a reason

Oestradiol and progesterone

Oestradiol is your main oestrogen, and progesterone rises after ovulation. Both swing widely through your cycle. That's why oestradiol is measured on day 2 to 5 (day 1 is the first day of your period) and progesterone about 7 days before your next period, around day 21 of a 28-day cycle. In 107 women, a single progesterone level of about 16 nmol/L or higher was a reliable sign that ovulation had taken place.

Reference range: oestradiol follicular phase 77-921 pmol/L · progesterone luteal phase 3.8-51 nmol/L (varies by lab) · GP: only with a reason

Prolactin

Prolactin is the hormone that controls milk production. In women, a high level can go together with irregular or missed periods. According to the guideline, about 4 in 10 high results are due to macroprolactin, a large form that is less active. Stress during the blood draw can also raise the level.

Reference range: women 110-560 mU/L (varies by lab) · GP: only with a reason

Aldosterone

Aldosterone is an adrenal hormone that controls your salt and fluid balance, and with it your blood pressure. Doctors read it together with renin, because a single value says little. Among 1,672 people with high blood pressure from GP practices, 6 in 100 made too much aldosterone. The 2025 guideline advises testing everyone with high blood pressure for this.

Reference range: 56-660 pmol/L · read as the aldosterone-renin ratio (varies by lab) · GP: not standard

LDL and non-HDL cholesterol

LDL is the cholesterol that can build up in your artery walls. Non-HDL counts all the cholesterol that can do this, so LDL plus the rest. In more than 184,000 women, the 30-year risk of heart and vascular disease rose from 8% with a non-HDL below 2.6 mmol/L to 34% at 5.7 or higher.

Reference range: LDL below 3.0 · non-HDL below 3.8 · total cholesterol below 5.0 mmol/L (varies by lab) · Total/HDL ratio: below 5 (some labs below 4) · GP: only with a reason

HDL cholesterol

HDL carries cholesterol from your blood vessels back to your liver. In more than 116,000 Danes, both a low and an extremely high HDL were linked to higher mortality. In women, mortality was lowest around 2.4 mmol/L and higher from 3.5 upwards.

Reference range: women above 1.2 · men above 1.0 mmol/L (varies by lab) · GP: only with a reason

Triglycerides

Triglycerides are fats in your blood. The level rises after a meal. In 26,509 healthy American women, triglycerides measured 2 to 4 hours after eating were most strongly linked to later heart and vascular disease. Fasting values added little on top of other risk factors.

Reference range: below 1.7 mmol/L (women and men; varies by lab) · GP: only with a reason

Fasting glucose

Your blood sugar after a night without food. In data from almost 700,000 people, a fasting glucose between 3.9 and 5.6 mmol/L was not linked to heart disease. Above that, the risk rose slightly. Diabetes roughly doubled the risk of heart disease, and the link was stronger in women than in men.

Reference range: below 6.1 mmol/L · 6.1-6.9 raised · 7.0 or higher is the diabetes threshold (NHG) · GP: only with a reason

Insulin and HOMA-IR

Insulin is the hormone that moves sugar from your blood into your cells. HOMA-IR is a calculation from your fasting glucose and insulin that estimates insulin resistance. The 2023 international PCOS guideline calls the usual insulin tests inaccurate and advises against them in routine care, so a single result says little.

Reference range: fasting insulin below 17 mU/L (varies by lab) · HOMA-IR: no fixed Dutch cut-off · GP: not standard

Creatinine

Creatinine is a waste product from your muscles that your kidneys clear. The lab converts it into your kidney function, the eGFR. In data from more than 105,000 people, an eGFR below 60 was linked to higher mortality. Between 75 and 105 there was no difference.

Reference range: women 45-84 · men 59-104 µmol/L · an eGFR below 60 counts as reduced (varies by lab) · GP: only with a reason

Sodium and albumin

Sodium controls the fluid balance in your body. Albumin is the main protein in your blood. Among 488 Boston Marathon runners, 13% had a low sodium at the finish, mostly those who gained weight during the race, a sign of drinking too much. A low albumin mainly reflects inflammation or illness, and says little about how much protein you eat.

Reference range: sodium 135-145 mmol/L · albumin 35-52 g/L (varies by lab) · GP: only with a reason

TSH, free T4 and free T3

TSH is the signal from your brain to your thyroid. Free T4 and free T3 are the hormones your thyroid makes itself. A clearly underactive thyroid is a well-known cause of fatigue. For a mild deviation, treatment didn't ease symptoms across 21 studies.

Careful. Do you take biotin (vitamin B7), for example in a hair, skin or nail supplement? It can make thyroid and other hormone results falsely high or falsely low. Tell your doctor or the lab before your blood test.

Reference range: TSH 0.27-4.2 mU/L · free T4 and free T3 vary by lab · GP: only with a reason, usually TSH only

hs-CRP

A sensitive measure of low-grade inflammation in your body. Among 4,847 British civil servants without fatigue, those with a CRP of 1 mg/L or higher had 28% higher odds of becoming fatigued over the next 3 years.

Reference range: CRP below 5-10 mg/L (varies by lab) · sensitive cut-offs 1 and 3 mg/L · GP: regular CRP, only with a reason

Haemoglobin and full blood count

Haemoglobin is the protein that carries oxygen in your blood. The full blood count also shows how big your red blood cells are and how much haemoglobin they hold (MCV, MCH, MCHC), plus how many white blood cells and platelets you have. Iron-deficiency anaemia is common in women who menstruate and is a well-known cause of fatigue.

Reference range: Hb women 7.5-10.0 · men 8.5-11.0 mmol/L (varies by lab) · GP: Hb standard, full blood count only with a reason

Ferritin, iron and transferrin

Ferritin is your iron store. Iron and transferrin show how much iron your blood is carrying at that moment. In 198 women with fatigue and a ferritin below 50 µg/L, fatigue eased more with iron than with placebo, even without anaemia.

Reference range: ferritin women 20-150 · men 25-250 µg/L (varies by lab) · Iron women 9-30 µmol/L · transferrin 1.8-3.8 g/L · transferrin saturation below 45% · GP: only with a reason, usually if Hb is low

ALT and GGT

ALT and GGT are liver enzymes in your blood. Doctors use them as a sign of strain on your liver. Across 19 studies with more than 9 million people, a higher GGT was linked to higher mortality. For ALT, the link differed by region.

Reference range: ALT up to 34 · GGT up to 35 U/L (women; men ALT up to 45 · GGT up to 40; varies by lab) · GP: only with a reason

Vitamin D

Your body makes vitamin D mostly in your skin, under the influence of sunlight. In 120 young adults with a level below 50 nmol/L, fatigue eased more after a single dose of vitamin D than after placebo. Experts don't agree on the best target.

Reference range: 30 nmol/L or higher (Dutch Health Council) · many labs 50-250 nmol/L · GP: not standard

Vitamin B12 and MMA

Vitamin B12 is needed for your nerves and red blood cells. A B12 level on its own doesn't tell the whole story. MMA rises when your cells are truly short of B12. In people without a clear deficiency, extra B12 didn't help memory or mood across 16 studies.

Reference range: B12 145-569 pmol/L · grey zone 148-260 · MMA below 0.45 µmol/L (varies by lab) · GP: only with a reason

Vitamin B2 and B6

B2 and B6 contribute to normal energy metabolism. In 123 young British women with low B2 status, haemoglobin rose as their B2 status improved. In a large American study, women of childbearing age had lower B6 levels than men, and most women on the pill had a low B6.

Careful. Too much B6 from supplements can cause nerve symptoms, such as tingling or numbness in your hands and feet. B6 is in many multivitamins and sports products, so add them all up. Discuss a high B6 result with your doctor.

Reference range: B2 200-375 nmol/L · B6 35-110 nmol/L (varies by lab) · GP: not standard

Vitamin A

Vitamin A is needed for your eyes, skin and immune system. Your liver keeps the blood level steady for a long time and inflammation can lower the result, so the level only partly reflects your stores. In 22,748 pregnant women, a lot of vitamin A from supplements in the early weeks was linked to more birth defects.

Careful. Pregnant or trying to conceive? The Netherlands Nutrition Centre advises no liver, only a little liver products such as liver sausage and pâté, and no supplements with vitamin A. If you take a supplement, choose one made for pregnancy.

Reference range: 1.0-4.2 µmol/L (varies by lab) · GP: not standard