Side effects depend on the strength you are on and how it is delivered. Commonly reported ones include acne or oilier skin, fluid retention, soreness at the injection or insertion site, breast tenderness, and changes to mood or sleep, and these often settle once the strength is adjusted. Testosterone also raises red blood cell levels in some men and suppresses your body’s own production, which is why follow-up labs and the fertility conversation are built into the plan rather than left until later. Less common risks vary with your age and your personal and family health history, which your doctor reviews before you start. Tell your doctor about anything new so the plan can be adjusted.