Testosterone Blood Test

What is a testosterone test?

A testosterone blood test measures the level of testosterone circulating in your blood. Total testosterone measures both bound (attached to proteins) and free testosterone. Free testosterone is the biologically active portion. Testing is done in the morning (7-10am) when levels peak. In men, testosterone is primarily produced by the testes. In women, it is produced in smaller amounts by the ovaries and adrenal glands.

Testosterone normal range

Other tests done with testosterone

Questions to ask your doctor

• Is my testosterone result truly low or within normal for my age?
• Do I need LH, FSH and prolactin tested too?
• Am I a candidate for testosterone replacement therapy?
• Could my medication (opioids, steroids, antidepressants) be lowering my testosterone?
• If I am a woman with high testosterone, do I need an ultrasound for PCOS?

Frequently asked questions

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

1. Male Hypogonadism. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK532933

References

Sources cited on this page. PubMed links open the original abstract.

1. Bhasin S, Cunningham GR, Hayes FJ, et al. Testosterone therapy in men with androgen deficiency syndromes: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2010;95(6):2536–2559. PMID 20525905 · doi:10.1210/jc.2009-2354

Why a single testosterone result is not enough

Testosterone has a pronounced diurnal rhythm in men: levels peak in the early morning (7–9 am) and decline throughout the day, with afternoon values up to 30–35% lower than morning levels. NICE and the British Society for Sexual Medicine guidelines require that low testosterone be confirmed on at least two separate morning fasting samples before a diagnosis of hypogonadism is made – a single low afternoon result is not diagnostic.

Additionally, approximately 40–60% of circulating testosterone is tightly bound to sex hormone-binding globulin (SHBG) and is biologically inactive. Another 40–50% is loosely bound to albumin (bioavailable). Only 1–3% is free testosterone, the pharmacologically active fraction. When SHBG is altered – raised in hyperthyroidism, liver disease, and ageing; lowered in obesity, hypothyroidism, and insulin resistance – total testosterone may not reflect androgen bioavailability. In these cases, free testosterone calculation (using a validated formula from total testosterone, SHBG, and albumin) or direct free testosterone measurement is needed.

The ADAM questionnaire and symptom assessment

Biochemical testosterone deficiency without symptoms should generally not be treated. The Androgen Deficiency in Aging Males (ADAM) questionnaire and the Aging Males' Symptoms (AMS) scale are standardised tools used to assess symptom burden before and during testosterone replacement therapy (TRT). Key symptoms of testosterone deficiency include: reduced libido, erectile dysfunction, fatigue, depressed mood, poor concentration, reduced muscle mass and strength, increased abdominal fat, and – with severe or prolonged deficiency – osteoporosis and anaemia. The decision to treat is based on the combination of low biochemical levels and clinically significant symptoms.

Testosterone in women – a growing clinical role

Testosterone is often thought of as purely a male hormone, but women produce testosterone in the ovaries and adrenal glands, and it plays an important role in libido, energy, and bone density. In postmenopausal women, testosterone levels decline alongside oestrogen. NICE guideline NG23 recommends offering testosterone supplementation to postmenopausal women with reduced sexual desire that is not improved by HRT alone. Testing in women uses lower reference ranges – female testosterone levels are approximately 10–20-fold lower than male – and must be interpreted with sex-specific reference intervals.