Testosterone Parameters
| Test | Men Normal | Women Normal | Notes |
|---|---|---|---|
| Total testosterone | 10–35 nmol/L | 0.5–2.4 nmol/L | Morning fasting sample |
| Free testosterone | 0.2–0.6 nmol/L | 5–35 pmol/L | Biologically active fraction |
| SHBG (sex hormone binding globulin) | 17–66 nmol/L | 26–110 nmol/L | Binds testosterone — high SHBG = low free T |
| LH | 1.7–8.6 IU/L | Varies by cycle | Distinguishes primary from secondary hypogonadism |
| FSH | 1.5–12.4 IU/L | Varies by cycle | Testicular/ovarian function |
Low Testosterone in Men (Hypogonadism)
- Primary hypogonadism: testicular failure (Klinefelter's syndrome, mumps orchitis, trauma) — high LH, low testosterone
- Secondary hypogonadism: hypothalamic-pituitary failure (pituitary tumour, haemochromatosis, obesity) — low LH, low testosterone
- Late-onset hypogonadism: age-related testosterone decline (begins ~1% per year after 40)
- Symptoms: low libido, erectile dysfunction, fatigue, low mood, reduced muscle/bone, central obesity, poor concentration
Always Test in the MorningTestosterone follows a diurnal rhythm, peaking at 8–10am. A sample taken in the afternoon may be 20–30% lower and can lead to false diagnosis of hypogonadism. Always retest fasting, morning samples.
Testosterone in Women
While testosterone is a 'male hormone', women produce it in adrenal glands and ovaries. Low testosterone in women is associated with low libido, fatigue, and reduced bone density. HIGH testosterone in women suggests PCOS, congenital adrenal hyperplasia, or (rarely) an androgen-secreting tumour.
What is a normal testosterone level for a man?
Morning fasting total testosterone of 10–35 nmol/L is normal. Levels <8 nmol/L in a symptomatic man are consistent with hypogonadism. 8–12 nmol/L is borderline — repeat and check free testosterone and SHBG.
Does obesity lower testosterone?
Yes. Adipose tissue converts testosterone to oestrogen (aromatisation) and increases SHBG production. Weight loss significantly raises testosterone — often into normal range without medication.
What are the risks of testosterone replacement therapy?
TRT increases red cell count (polycythaemia), may impair fertility (suppresses LH/FSH and sperm production), worsens sleep apnoea, and may affect cardiovascular risk. Long-term prostate cancer risk remains debated.
Why do women need testosterone?
Women produce testosterone for libido, energy, bone density, and muscle maintenance. Female testosterone deficiency is an evolving area — NICE recommends considering testosterone for postmenopausal women with hypoactive sexual desire disorder.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.