Normal Testosterone Levels by Age: How to Read Your Lab Results

What does a testosterone blood test measure?

A standard testosterone test measures total testosterone — the sum of testosterone bound to proteins in the blood (mainly sex hormone-binding globulin, or SHBG) and the small free fraction. Total testosterone is the standard first test.

Free testosterone — the biologically active fraction — is sometimes measured separately, particularly when SHBG is known to be altered. Obesity, diabetes, and hypothyroidism lower SHBG; liver disease or hyperthyroidism raise it, potentially masking a low free testosterone.

Bioavailable testosterone combines free testosterone with loosely bound (albumin-bound) testosterone and is another measure some clinicians use.

For most men with straightforward symptoms, total testosterone measured correctly is the appropriate starting point 1Ref 1Bhasin S, Brito JP, Cunningham GR, et al. (2018).Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.Definition of hypogonadism at below ~300 ng/dL; requirement for two morning confirmatory samples; factors causing transient low testosterone; caution about treating older men with borderline levels.

What is the normal range for total testosterone?

Reference ranges vary somewhat by laboratory and assay method, which is one reason a number in one lab's report may not map exactly to another. The Endocrine Society guideline defines hypogonadism as a total testosterone level below approximately 300 ng/dL (roughly 10.4 nmol/L) in a symptomatic man, confirmed on two separate morning samples 1Ref 1Bhasin S, Brito JP, Cunningham GR, et al. (2018).Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.Definition of hypogonadism at below ~300 ng/dL; requirement for two morning confirmatory samples; factors causing transient low testosterone; caution about treating older men with borderline levels.

The AUA guideline on testosterone deficiency uses a similar threshold, noting that most clinical studies and guideline panels converge on values below 300 ng/dL as the working definition of low 2Ref 2Mulhall JP, Trost LW, Brannigan RE, et al. (2018).Evaluation and Management of Testosterone Deficiency: AUA Guideline.AUA convergence on below 300 ng/dL as the diagnostic threshold; morning testing requirement; confirmatory testing protocol.

Note that reference ranges printed on your lab report may list a broader range and include all adult men regardless of symptoms. A number within the printed reference range is not automatically proof that testosterone is sufficient for you specifically.

How does testosterone change with age?

Total testosterone declines gradually with age in men. The Massachusetts Male Aging Study — a large longitudinal cohort following more than 1,700 men over 7–10 years — documented a mean decline of approximately 1.6% per year in total testosterone 3Ref 3Feldman HA, Longcope C, Derby CA, et al. (2002).Age Trends in the Level of Serum Testosterone and Other Hormones in Middle-Aged Men: Longitudinal Results from the Massachusetts Male Aging Study.Longitudinal documentation of testosterone decline with age (~1.6%/year total testosterone; ~2–3%/year free testosterone) from a large representative cohort of over 1,700 men. Free testosterone declines more steeply, at roughly 2–3% per year.

Individual variation is large: many men in their 60s and 70s maintain levels well within the normal adult range. The gradual age-related decline differs from a sudden drop caused by a specific disease process — a distinction that matters for how the result is interpreted.

The Endocrine Society guideline is cautious about treating older men with borderline levels without clear symptoms, given the limited evidence for benefit and the real risks of therapy 1Ref 1Bhasin S, Brito JP, Cunningham GR, et al. (2018).Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.Definition of hypogonadism at below ~300 ng/dL; requirement for two morning confirmatory samples; factors causing transient low testosterone; caution about treating older men with borderline levels.

Why does the time of day matter for the test?

Testosterone follows a circadian rhythm, with the highest levels in the early morning (typically 7–10 a.m.) and declining through the day. A blood draw at noon or in the afternoon may produce a value 15–30% lower than a morning sample. For this reason, both major guidelines 1Ref 1Bhasin S, Brito JP, Cunningham GR, et al. (2018).Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.Definition of hypogonadism at below ~300 ng/dL; requirement for two morning confirmatory samples; factors causing transient low testosterone; caution about treating older men with borderline levels2Ref 2Mulhall JP, Trost LW, Brannigan RE, et al. (2018).Evaluation and Management of Testosterone Deficiency: AUA Guideline.AUA convergence on below 300 ng/dL as the diagnostic threshold; morning testing requirement; confirmatory testing protocol specify that testosterone testing should be done in the morning — ideally fasting.

If your result was drawn in the afternoon, a low value should be rechecked in the morning before any diagnosis or treatment decision is made.

What else can affect testosterone levels?

Several factors — other than true hypogonadism — can temporarily lower testosterone:

• Acute illness or hospitalization
• Severe obesity (often lowers both total testosterone and SHBG)
• Opioid medications (suppress the HPG axis significantly)
• Heavy alcohol use
• Very recent high-intensity exercise (acutely)
• Caloric restriction or extreme weight loss
• Sleep deprivation

For this reason, guidelines recommend checking testosterone when the person is in their usual health state, not during an acute illness, and confirming a low result on a second morning sample before concluding that hypogonadism is present 1Ref 1Bhasin S, Brito JP, Cunningham GR, et al. (2018).Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.Definition of hypogonadism at below ~300 ng/dL; requirement for two morning confirmatory samples; factors causing transient low testosterone; caution about treating older men with borderline levels.

What happens after a confirmed low result?

If two morning testosterone levels are low and you have compatible symptoms, the next step is determining the cause. The evaluation includes LH and FSH (to distinguish between primary testicular failure and secondary hypothalamic/pituitary causes), prolactin, and sometimes pituitary imaging if LH/FSH are unexpectedly low.

This evaluation is typically done by a primary care clinician or an endocrinologist. Treatment decisions — including whether and how to use testosterone therapy — depend on the cause, the severity of symptoms, and your individual health situation. Gale's primary care clinicians can order the appropriate labs and help you navigate next steps.