SYNTHETIC DEMONSTRATION — no real student or patient. Not a medical device.

endocrine

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

Most labs report testosterone in ng/dL, with a broadly used reference range of approximately 300–1000 ng/dL for adult men. What counts as 'low' depends on the assay, symptoms, time of day the blood was drawn, and age. Guidelines recommend confirming with a second morning sample before making any treatment decisions based on a single low result.

Talk to a clinician

Nina Osei, NP — Nurse Practitioner

checkups, refills & skin. Gale can match you with a licensed clinician for a visit.

Find care →

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 1.

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 1.

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 2.

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 3. 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 1.

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 12 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 1.

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.

Common questions

Is 400 ng/dL a normal testosterone level?

Yes, 400 ng/dL falls within the broadly accepted adult male reference range of approximately 300–1000 ng/dL. Whether it is adequate for you individually depends on your symptoms and other factors your clinician can assess.

Should I check testosterone if I feel fine but want to know my baseline?

Routine screening of asymptomatic men is not currently recommended by major guidelines. Testing is most meaningful when done in the context of symptoms that may be related to testosterone deficiency.

Can testosterone be too high?

Yes. Elevated testosterone in men (above roughly 1000–1200 ng/dL, depending on the lab) can occur with testosterone-secreting tumors, anabolic steroid use, or overtreatment with testosterone therapy. Symptoms of excess include acne, elevated red blood cell count, irritability, and testicular atrophy from suppression of natural production.

Do testosterone home tests work?

Some at-home kits measure testosterone from saliva or a finger-prick blood sample. Accuracy varies and results from these tests are not directly comparable to serum testosterone measured in a certified clinical lab. If you have symptoms, a properly timed serum test through a clinician is the reliable option.

Talk to a clinician

Nina Osei, NP — Nurse Practitioner

checkups, refills & skin. Gale can match you with a licensed clinician for a visit.

Find care →

Important testing and interpretation notes

  • —A single low testosterone result is not enough for a diagnosis — guidelines require two morning samples
  • —Testosterone results drawn in the afternoon may appear falsely low
  • —Very low testosterone (below 150 ng/dL) with new onset should prompt evaluation for a pituitary tumor or testicular failure
  • —Do not start testosterone supplementation based on a home test or a single result without clinician review

This article explains how testosterone lab values are interpreted generally. Your lab report and your symptoms must be evaluated together by a clinician. Reference ranges differ by laboratory.

References

  1. 1.Bhasin S, Brito JP, Cunningham GR, et al. (2018). Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism. doi:10.1210/jc.2018-00229 ✓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
  2. 2.Mulhall JP, Trost LW, Brannigan RE, et al. (2018). Evaluation and Management of Testosterone Deficiency: AUA Guideline. Journal of Urology. doi:10.1016/j.juro.2018.03.115 ✓AUA convergence on below 300 ng/dL as the diagnostic threshold; morning testing requirement; confirmatory testing protocol
  3. 3.Feldman 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. Journal of Clinical Endocrinology & Metabolism. doi:10.1210/jcem.87.2.8201 ✓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

3 sources, numbered by first appearance. General health information, not medical advice — synthetic demonstration content.