Testosterone

Also written as: Total testosterone, T

The main androgen hormone, measured for questions about energy, fertility, and hormonal balance.

What it measures

The concentration of testosterone, the main androgen (masculinizing) hormone, in the blood. Most tests measure total testosterone, which includes both the portion bound to carrier proteins and the small free portion that is biologically active.

Why a doctor orders it

Ordered in men when low energy, low libido, fertility problems, or erectile difficulties raise the question of low testosterone, and in women when symptoms such as excess hair growth or irregular periods raise the question of androgen excess. Often paired with other hormone tests to see where in the system a change originates.

What is generally associated with a higher result

Broadly associated with androgen excess conditions such as polycystic ovary syndrome in women, with testosterone or anabolic steroid use, and with certain adrenal or ovarian conditions. In men, mildly raised values are often of little significance.

What is generally associated with a lower result

Broadly associated in men with reduced production from the testes or reduced pituitary signaling, but also with aging, higher body weight, poor sleep, recent illness, and certain medications. In women, low values are generally not pursued.

Everyday things that move this number

Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:

Time of day - levels are naturally highest in the early morning
Recent illness, poor sleep, or heavy exercise
Body weight and significant recent weight change
Opioid pain medications and steroid medications
Biotin supplements, which can interfere with some lab methods

Questions to take to your appointment

Was this drawn in the morning, when levels are most reliable?
Should free testosterone or SHBG, its carrier protein, be measured alongside the total?
Could a medication I take, such as an opioid or a steroid, be influencing this?

Build a printable questionnaire with your own results →

Where to read more

MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .

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