A man may take testosterone for several medical reasons, always under the supervision of a doctor. Some reasons include: Low testosterone levels (low T): This is often called hypogonadism and can cause symptoms like low sex drive, erectile dysfunction, fatigue, and mood changes. Doctors may prescribe testosterone therapy to help alleviate low T symptoms and improve quality of life. Delayed puberty: If a male has not begun puberty by age 14, testosterone therapy may be used to induce the changes that occur during puberty like growth of the penis and testes, voice deepening, and hair growth. Muscle loss due to disease/aging: As some men age or have certain medical conditions, they lose muscle mass. Doctors may prescribe testosterone to help maintain muscle mass and strength. Breast cancer: For some forms of breast cancer responsive to hormonal therapy, testosterone may be used to help stop cancer cell growth. Bone marrow stimulation: Testosterone is used to produce red blood cells in bone marrow for some patients undergoing chemotherapy or with other blood disorders. A doctor determines if testosterone therapy is appropriate based on a man's age, symptoms, and hormone levels on lab tests. They will also consider potential risks like prostate issues, heart disease, sleep apnea, and testicular shrinkage. If prescribed, the testosterone is customized to the optimal dose, formulation (injection, patch, gel), and treatment plan for the individual patient. Follow up lab testing and doctor visits ensure treatment is working as intended without side effects. The decision to take testosterone is complex. A man should have an open discussion with his doctor about whether it aligns with his health needs and goals.