Understanding total testosterone
Total testosterone is one of the biomarkers most commonly included on a standard hormone panel. This page explains, in plain language, what the total testosterone measurement represents, how it relates to free testosterone and the proteins that carry it, the units you may see on a report, and public reference examples from published sources.
Everything here is educational context. It does not interpret what any particular value means, does not diagnose, and does not describe any course of action.
What total testosterone is
Testosterone is a steroid hormone produced mainly in the testes in males and the ovaries in females, with a smaller amount from the adrenal glands in both sexes.
The total testosterone measurement reports the combined amount of testosterone circulating in the blood — both the portion bound to carrier proteins and the small unbound portion.
How it differs from free testosterone
Free testosterone refers only to the unbound fraction. Total testosterone includes that free fraction plus the testosterone bound to proteins, so the two measurements describe different things and are often reviewed together for educational context.
Relationship to SHBG and albumin
Most circulating testosterone is bound to sex hormone-binding globulin (SHBG) and, more loosely, to albumin. Only a small unbound fraction is free. Because the amount of SHBG present varies between individuals, the proportion of testosterone that is bound versus unbound can differ even when the total measurement is similar. This is why total testosterone, free testosterone, and SHBG are often read together.
Why it is commonly measured
Total testosterone is commonly measured as part of a broader look at androgen status on a hormone panel. In research and clinical education it is often reviewed alongside several related markers that describe different parts of the hormonal axis:
- Free testosterone — the unbound fraction that pairs with the total measurement.
- SHBG — the main carrier protein that influences how much testosterone is bound.
- Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) — pituitary signals within the reproductive axis.
Because testosterone differs by sex and can vary with age, the measurement is read in the context of an individual's sex and age group. This page does not interpret what any particular value means and does not recommend any action. Any individual measurement should be discussed with a licensed healthcare provider.
Common units
Total testosterone is most often reported in one of two units:
- ng/dL (nanograms per deciliter) — commonly used in the United States.
- nmol/L (nanomoles per liter) — an SI unit common in many other countries.
Units and assay methods vary by laboratory, so always read the unit printed next to your own measurement. A figure expressed in one unit is not directly comparable to a figure in another unit without converting between them.
Public reference examples
The examples below are public reference examples drawn from published sources. They are labeled by the study population they came from. No single range applies to everyone, and they are shown for educational context only.
Reference ranges vary by laboratory, assay, age, sex, and population. These figures are public reference examples for education, not a universal standard and not a determination about any individual. Where a measurement is available, Pepvela prioritizes the reference range printed on your own lab report.
Age and sex context
Testosterone reference intervals differ substantially between males and females, and they may also vary with age, the laboratory method used, and the population studied. A figure drawn from one age group, sex, or assay may not correspond to another.
For this reason, total testosterone is read within the reference interval that matches the individual and the specific laboratory performing the measurement, rather than against a single fixed number.
Related biomarkers
These related biomarkers are often reviewed alongside total testosterone for educational context:
Free testosterone is currently covered on the combined Testosterone page. A dedicated Free Testosterone page is planned.
Related peptide research
Research literature involving certain compounds may measure testosterone-related markers as endpoints. The following research pages are provided for educational context only and make no claim about any effect on testosterone:
Citations
- MedlinePlus. Testosterone Levels Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/testosterone-levels-test/
- Nassar GN, Leslie SW. Physiology, Testosterone. StatPearls. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK526128/
- Travison TG, Vesper HW, Orwoll E, et al. Harmonized Reference Ranges for Circulating Testosterone Levels in Men of Four Cohort Studies in the United States and Europe. J Clin Endocrinol Metab. 2017;102(4):1161–1173. https://pubmed.ncbi.nlm.nih.gov/28324103/
- Braunstein GD, Reitz RE, Buch A, Schnell D, Caulfield MP. Testosterone reference ranges in normally cycling healthy premenopausal women. J Sex Med. 2011. https://pubmed.ncbi.nlm.nih.gov/21771278/