A longevity researcher started taking testosterone in his 50s and lists four things to know before considering TRT.

Matt Kaeberlein, a longevity researcher, began testosterone replacement in his early 50s after tests showed primary hypogonadism; he tried supplements and an oral medication before settling on weekly injections and reports improved energy and body composition.

Matt Kaeberlein, a longevity researcher, began exploring testosterone replacement after noticing low energy, reduced libido, and limited changes in body composition in his early 50s. He first had a common total testosterone blood test that was in the lower half of the reference range and was told he did not need treatment. He later ordered a free testosterone panel and was diagnosed with primary hypogonadism. After trying supplements and an oral medication, he now uses weekly testosterone injections and reports improvements. Key details: - He experienced symptoms including low energy, reduced libido, and difficulty changing body composition despite regular strength training and a balanced diet. - An initial "total testosterone" test showed low-normal results; a later "free testosterone" panel indicated primary hypogonadism. - He tried supplements and an oral testosterone product (Jatenzo) before transitioning to weekly injections under medical care. - Injected synthetic testosterone can suppress the pituitary signals that support sperm production and can lead to infertility; regaining sperm production after stopping therapy can take months or years and may not fully return in some cases. - Around the time he began injections he reduced alcohol intake and became more regimented with exercise, and he reports improved energy, libido, and body composition. Summary: Kaeberlein's experience highlights variability in testing and treatment pathways for low testosterone, and underscores differences between total versus free testosterone testing and the potential reproductive effects of replacement therapy. He continues weekly injections and worked with a doctor to adjust his plan while also changing lifestyle habits. Undetermined at this time.