Testosterone (Total)

What is testosterone?

Testosterone is a steroid hormone belonging to the androgen family. In males, it is produced primarily by the Leydig cells in the testes, with a small contribution from the adrenal glands. In females, it is produced by the ovaries and adrenal glands in considerably smaller quantities. In both sexes, testosterone production is regulated by the hypothalamic-pituitary-gonadal axis through a classical negative feedback loop involving LH (luteinising hormone) and FSH (follicle-stimulating hormone).

Testosterone drives the development of male secondary sexual characteristics during puberty, but its roles extend far beyond reproduction. It is critical for maintaining bone density, muscle mass and strength, red blood cell production, mood and cognitive function, and libido in both sexes. These roles explain why both deficiency and excess have significant clinical consequences.

The blood test measures total testosterone — both the biologically active free fraction and that which is bound to carrier proteins (primarily sex hormone-binding globulin, SHBG, and albumin). In some clinical contexts, measuring free testosterone or SHBG alongside total testosterone provides additional insight, particularly in obesity, where high SHBG can cause free testosterone to be disproportionately low despite a borderline total level.

Because testosterone follows a pronounced diurnal rhythm, peaking in the early morning and declining through the afternoon, the timing of sample collection is important for accurate interpretation. Blood should ideally be drawn before 10am.

Normal reference range

• Adult males: 10–35 nmol/L
• Adult females: 0.3–2.4 nmol/L

Important: Reference ranges vary between laboratories and depend on individual factors including age, sex, pregnancy status, and medication. Always interpret your result in the context of a clinician review. The Vesey reviews every result before release.

What low testosterone in males may indicate

Low testosterone in males (below approximately 8–10 nmol/L on a morning sample) is termed hypogonadism. Causes include:

• Primary hypogonadism — testicular failure due to Klinefelter syndrome, mumps orchitis, chemotherapy, or radiation
• Secondary (hypogonadotrophic) hypogonadism — failure of the pituitary to adequately stimulate testosterone production, seen in hypopituitarism, prolactinoma, or kallmann syndrome
• Age-related decline (late-onset hypogonadism) — testosterone naturally declines approximately 1–2% per year after age 30
• Obesity — adipose tissue converts testosterone to oestrogen, and SHBG is typically lower, reducing total testosterone
• Anabolic steroid use — exogenous androgens suppress the hypothalamic-pituitary axis, leading to secondary testicular atrophy
• Chronic illness — severe systemic disease, diabetes, and opioid medication can all suppress testosterone

Symptoms of low testosterone include fatigue, low libido, erectile dysfunction, reduced muscle mass, increased abdominal fat, depression, and impaired concentration.

What high testosterone in females may indicate

Testosterone above 2.4 nmol/L in a female requires investigation. Common and important causes include:

• Polycystic ovary syndrome (PCOS) — the most common cause, affecting approximately 1 in 10 women; elevated testosterone drives hirsutism, acne, and menstrual irregularity
• Congenital adrenal hyperplasia (CAH) — an inherited enzyme deficiency causing excess androgen production from the adrenal glands
• Adrenal or ovarian tumours — androgen-secreting tumours are rare but important to exclude with markedly elevated levels
• Cushing's syndrome — excess cortisol production is often accompanied by androgen excess
• Anabolic steroid use — deliberate or inadvertent use of androgen-containing preparations

Get tested at The Vesey, Sutton Coldfield

Testosterone is measured within the following panels at The Vesey Private Hospital:

• Testosterone Monitoring panel — £148 (ideal for TRT monitoring and initial assessment)
• Hormone Profile — testosterone plus LH, FSH, SHBG, and prolactin
• Advanced Health Panels (male) — comprehensive male health screen

Morning appointments recommended for most accurate results. Clinician-reviewed results released securely, typically within 24 hours.

Frequently asked questions

What is a normal testosterone level?

Normal total testosterone for adult males is 10–35 nmol/L. For adult females, 0.3–2.4 nmol/L. Levels peak in the early morning, so the test should ideally be taken before 10am for accuracy.

What are the symptoms of low testosterone in men?

Symptoms include persistent fatigue, reduced sex drive, erectile dysfunction, loss of muscle mass, increased abdominal fat, low mood or depression, reduced concentration, and poor sleep quality. These symptoms are non-specific and require blood testing alongside clinical assessment.

Why might a woman have high testosterone?

The most common cause is polycystic ovary syndrome (PCOS), affecting 1 in 10 women. Other causes include adrenal disorders, ovarian tumours, and anabolic steroid use. A thorough hormonal workup including LH, FSH, and androstenedione is typically performed alongside testosterone.

When is the best time to test testosterone?

Testosterone follows a diurnal rhythm, peaking between 7am and 10am. Blood should be taken in the morning for accurate baseline assessment. An afternoon result may be misleadingly low and lead to unnecessary concern.

What is the difference between total testosterone and free testosterone?

Total testosterone includes both bound and free (biologically active) fractions. Most testosterone is bound to SHBG and albumin. Free testosterone — which is what cells can actually use — may be disproportionately low in obesity (low SHBG) or high in PCOS. Your clinician may request SHBG alongside total testosterone to calculate free testosterone if the clinical picture suggests it.