Potential side effects include erectile dysfunction, loss of ability to ejaculate, loss of libido, infertility, weight gain, mood swings, depression, increased risk of deep vein thrombosis, increased risk of breast cancer.
HRT for trans men consists of testosterone administered most commonly through injections (the cheapest, safest option) in periods ranging from one week to four months depending on the formulation.
As an example, one batch of testosterone purchased online was tested and discovered to be petrol.
While pill options are available, they are advised against due to their connection to liver damage.
Based on anecdotal reports, testosterone dulls perceived temperature by about two to three degrees.
Testosterone may also have a slight dulling effect on senses of smell and touch, and vice versa.
HRT thus also affects blood test results, which should be measured against that of others of that sex.
In 2014, a long term study of 1,600 transgender people on HRT established it as safe.