Total testosterone
Testosterone, also known as "serum testosterone" and "total testosterone", is a blood test that measures the amount of testosterone in the blood. It is used for dosing many of the medications used by transgender people.
In those who take masculinising hormone therapy, low testosterone levels may lead to slower masculinization, while high testosterone levels may cause several dangerous health problems, like polycythemia (too many red blood cells) (Madsen et al., 2021).
In those who take feminizing hormone therapy, high testosterone levels may lead to slower feminization.
Expected values
Target values may differ between different countries, transgender health guidelines, and timings- and formulations of testosterone. The widely used Endocrine Society guidelines recommend that:
- In transfeminine people, testosterone should be maintained below 50 ng/dL (1.7 nmol/L)
- In transmasculine people, testosterone levels should be maintained around 320 - 1000 ng/dL (11 - 35 nmol/L).
These values are similar to those found in cisgender men and women. (Hembree at al., 2017)
Other information
This blood test is often confused with "free testosterone": a different blood test that is rarely used in transgender healthcare.
See also
References
- Hembree, W. C., Cohen-Kettenis, P. T., Gooren, L., Hannema, S. E., Meyer, W. J., Murad, M. H., Rosenthal, S. M., Safer, J. D., Tangpricha, V., & T'Sjoen, G. G. (2017). Endocrine Treatment of Gender-Dysphoric/Gender-Incongruent Persons: An Endocrine Society Clinical Practice Guideline. The Journal of Clinical Endocrinology and Metabolism, 102(11), 3869–3903. [DOI:10.1210/jc.2017-01658]
- Madsen, M. C., van Dijk, D., Wiepjes, C. M., Conemans, E. B., Thijs, A., & den Heijer, M. (2021). Erythrocytosis in a Large Cohort of Trans Men Using Testosterone: A Long-Term Follow-Up Study on Prevalence, Determinants, and Exposure Years. The Journal of clinical endocrinology and metabolism, 106(6), 1710–1717. [DOI:10.1210/clinem/dgab089]