Blood tests
What your testosterone result actually means: reference ranges explained
When your blood test report shows a testosterone level next to a "reference range", it's easy to assume the range is a fixed, universal definition of normal. In practice, a reference range is a statistical description of one laboratory's own sample of people. On its own, it isn't a diagnosis.
4 min read
How much do ranges differ between laboratories?
In 2006, researchers asked 25 laboratories for their testosterone reference ranges. They got back 17 different ranges for total testosterone and 13 for free testosterone, even though many of the labs used the same testing methods and equipment.
- The lower limit of the "normal" range for total testosterone ranged from 130 to 450 ng/dL (about 4.5 to 15.6 nmol/L), a difference of roughly 350%.
- The upper limit ranged from 486 to 1,593 ng/dL (about 16.9 to 55.3 nmol/L), a difference of roughly 325%.
Australian reports use nmol/L. In practice, the same blood sample could be reported as "low" by one laboratory and "within range" by another, simply because the two labs use different cut-offs.
What a reference range is, and isn't
A reference range usually comes from the middle 95% of results in a group of people the laboratory considers healthy. It describes that group. It isn't automatically the level at which symptoms usually appear.
Many things affect a measured result and how it should be read: age, the time of day the blood was taken, the testing method, the level of a carrier protein called sex-hormone-binding globulin (SHBG), and any illness at the time.
Professional bodies have been moving towards more standardised testing, such as more precise lab methods and ranges based on large population studies. Even so, the range printed on your report is still specific to that laboratory, not a stand-alone diagnosis.
Why this matters
Low testosterone is diagnosed from a combination of consistent symptoms and confirmed low morning results, usually on more than one occasion, considered alongside your overall health. A single number just above or below one lab's cut-off doesn't, on its own, confirm or rule anything out. Repeat testing, additional measures when they're needed, and a practitioner's judgement all matter.
This article is general information only. It isn't personal medical advice. Always talk to a registered practitioner about what your own results mean and whether any further tests are needed.
References
- Lazarou S, Reyes-Vallejo L, Morgentaler A. Wide variability in laboratory reference values for serum testosterone. J Sex Med. 2006;3(6):1085-1089. doi:10.1111/j.1743-6109.2006.00334.x
- Travison TG, et al. Harmonized reference ranges for circulating testosterone levels in men of four cohort studies in the USA and Europe. J Clin Endocrinol Metab. 2017;102(4):1161-1173.
© 2026 EDGD PTY LTD. All rights reserved.