Total Testosterone
Testosterone is the main male sex hormone, though women make small amounts too. It helps shape sex drive, mood, muscle, and bone in both sexes. Levels naturally swing through the day and differ a lot by sex and age, so there is no one "normal" number — your result is read against the range on your report.
Targeted TestingWhat is total testosterone?
Testosterone is a steroid hormone — a type of chemical messenger your body makes from cholesterol. In males it is produced mainly by the testes, with a small amount from the adrenal glands (two small glands that sit on top of the kidneys). In females the adrenal glands and the ovaries each contribute. The pituitary gland (a pea-sized gland at the base of the brain) controls how much is made by releasing a signal hormone called luteinising hormone (LH). Testosterone circulates in two forms: most of it is bound to carrier proteins and held in reserve; only a small free fraction — roughly one to three per cent — is biologically active. A total testosterone test measures both forms together. The body can also convert testosterone to oestradiol (the main female sex hormone), which is why it matters in both sexes. In adult males testosterone supports sex drive and mood, bone and muscle strength, and the production of sperm and new blood cells. In females it plays a role in bone and muscle health and sex drive, even though levels are naturally much lower.
Why is it tested?
A total testosterone test is ordered when symptoms suggest the level may be out of the usual range. In men this can include persistent tiredness, reduced sex drive, or concerns about fertility. In women it is often tested as part of an investigation into excess body hair (hirsutism — more hair growth than expected in places typically associated with male-pattern hair), irregular periods, or difficulty conceiving. It is also used to look into delayed or unusually early puberty in boys. Timing of the sample is important. Testosterone follows a diurnal variation — a daily rhythm — with a morning peak and a mid-afternoon low point. For this reason, the blood draw is usually taken between 8 and 10 am. In men, a low result is typically confirmed on a second morning sample before any conclusions are drawn.
Reference range (Australia)
Testosterone is higher in the morning, with a peak between roughly 8 and 10 am and a mid-afternoon low (diurnal variation). Reference intervals differ markedly by sex — male intervals are substantially higher than female intervals — and shift across the lifespan in both sexes. A second morning sample is standard before acting on a low result in men. Use the interval printed on your own report, which is already adjusted for sex and your laboratory's analyser.
Reference intervals vary between laboratories. Always use the range printed on your own report.
What your result means
In men, testosterone naturally declines with age. A result below the reference interval can be associated with tiredness, reduced sex drive, or mood changes — often described as "low T" — though many of these symptoms have other causes too. Because the level varies so much through the day, a low reading is generally checked on a second morning sample before it is acted on. In women, testosterone is naturally low relative to men, and a result at the lower end of the female range is expected. The significance depends on the clinical picture your GP can see.
A result within the reference interval for your sex and age is the expected finding. If symptoms led to the test, it is worth a conversation with your GP — a normal testosterone is useful information, but symptoms may still have a cause worth exploring.
For men, a result above the reference interval can reflect natural daily variation or collection timing — the level is highest in the morning, so a sample drawn early may sit at the top of the range. A persistently raised result is worth discussing with your GP, who can look at it in context. For women, a higher-than-expected testosterone can relate to androgen-excess conditions — situations where the body is making or responding to more androgen (male-type hormone) than usual. These are medical patterns that need a clinical assessment with your GP, not something a single result can pin down on its own. Cycle timing and stress can also push the number up.
What can affect your result
Time of day is the biggest single variable: testosterone is highest in the first couple of hours after waking and falls through the afternoon. This is why the sample should be taken between 8 and 10 am for a reliable reading. Ageing matters too. Concentrations of sex hormone binding globulin (SHBG — the main carrier protein that holds testosterone in reserve) rise with age, which means the free, active fraction falls even when total testosterone stays in range. Other factors that can shift the number include oral contraceptives (which lower testosterone in women), significant illness or stress, sleep quality, and body weight. High-dose biotin supplements (a vitamin B7 supplement sometimes taken for hair and nails) can interfere with some laboratory assays and produce a misleading result. If you take them, your GP can take that into account when reading your result.
When to act
If your result is outside the reference interval on your report, it is worth a chat with your GP rather than a cause for immediate concern. A single out-of-range result is rarely the whole story — they will look at the timing of your sample, your symptoms, and any other relevant hormone results before deciding whether a repeat test or further investigation makes sense. This page is general information and is not a substitute for advice from your GP.
Frequently asked questions
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