Enarei

Complete (full) blood count

A complete blood count (CBC), or full blood count (FBC), is a blood test used to measure the number of red- and sometimes white blood cells in the body. Levels that are significantly outside the expected range can indicate a medical problem in some cases.

Expected values

Blood test results should be interpreted using the reference range from the laboratory that produced the result, as they can differ between laboratories. Approximate expected values are published by several organisations including the Gloucestershire Hospitals NHS Foundation Trust (UK) and the Mayo Clinic (US).

Because testosterone stimulates the production of red blood cells, expected values are higher in men, and lower in women (Bachman et al., 2014; Murphy, 2014).

When taking hormone therapy, trans people's results should be compared to the range that matches their hormone profile (male range for people who take testosterone; female range for people who take estrogen), not their sex assigned at birth. When trans people are incorrectly compared to the reference range of their birth sex, they may be misdiagnosed with conditions like anemia (Harper et al., 2021; Antun et al., 2020; Deutsch, 2016).

Other information

This blood test is especially important to people who take testosterone (and other androgens), as incorrect dosing can lead to dangerously high amounts of red blood cells. When this happens, a lower dose of testosterone, or different form of administration, may be required (Deutsch, 2016).

See also

References

  • Antun, A., Zhang, Q., Bhasin, S., Bradlyn, A., Flanders, W. D., Getahun, D., Lash, T. L., Nash, R., Roblin, D., Silverberg, M. J., Tangpricha, V., Vupputuri, S., & Goodman, M. (2020). Longitudinal Changes in Hematologic Parameters Among Transgender People Receiving Hormone Therapy. Journal of the Endocrine Society, 4(11), bvaa119. [DOI:10.1210/jendso/bvaa119]
  • Bachman, E., Travison, T. G., Basaria, S., Davda, M. N., Guo, W., Li, M., Connor Westfall, J., Bae, H., Gordeuk, V., & Bhasin, S. (2014). Testosterone induces erythrocytosis via increased erythropoietin and suppressed hepcidin: evidence for a new erythropoietin/hemoglobin set point. The journals of gerontology. Series A, Biological sciences and medical sciences, 69(6), 725–735. [DOI:10.1093/gerona/glt154]
  • Deutsch, M. B. (Ed.). (2016). Guidelines for the Primary and Gender-Affirming Care of Transgender and Gender Nonbinary People, 2nd Edition. San Francisco: University of California, San Francisco/UCSF Transgender Care. [URL] PDF]
  • Harper, J., O'Donnell, E., Sorouri Khorashad, B., McDermott, H., & Witcomb, G. L. (2021). How does hormone transition in transgender women change body composition, muscle strength and haemoglobin? Systematic review with a focus on the implications for sport participation. British journal of sports medicine, 55(15), 865–872. [DOI:10.1136/bjsports-2020-103106]
  • Murphy W. G. (2014). The sex difference in haemoglobin levels in adults - mechanisms, causes, and consequences. Blood reviews, 28(2), 41–47. [DOI:10.1016/j.blre.2013.12.003]