How do testosterone injections work? They place testosterone, the main male sex hormone, into muscle or just under the skin, where it slowly enters your bloodstream and replaces some of what your body is not making. This guide covers the hormone’s role, how injections are given, and what happens after a dose.
What Testosterone Does in Your Body
Testosterone is a hormone, a chemical messenger made mostly in the testicles. It helps regulate sex drive, muscle and bone, red blood cell production, and mood, and levels naturally vary from person to person and across the day. Cleveland Clinic explains that testosterone replacement therapy means taking manufactured testosterone to regulate low levels caused by male hypogonadism, a condition in which the testicles, or the brain areas that control them, do not produce enough. It also notes that treatment does not fix the underlying cause of low testosterone, so it is meant to be long term. As of 2025, it is not approved for age-related decline without an associated medical condition.
How Injections Are Given
Injections are one of several forms. Cleveland Clinic also lists skin gels, patches, pellets placed under the skin every three to six months, and tablets. Intramuscular injections, which go into a muscle, are typically given every one to two weeks in a medical office, and some long-acting versions are given about every ten weeks. Subcutaneous injections go just under the skin and are typically weekly. For testosterone cypionate, the FDA-approved label says to inject deep into the buttock muscle only. Your clinician picks the form and schedule after reviewing your health history, your preferences, and how comfortable you are with giving yourself injections, since some people do that at home after training.
What Happens After the Injection
Many injectable forms are testosterone attached to a fatty acid chain and dissolved in oil. According to the label, the hormone is absorbed slowly from that oil, and its elimination half-life, the time your body needs to clear half a dose, is about eight days. Your liver inactivates most of it, and active byproducts include dihydrotestosterone (DHT) and estradiol, a form of estrogen. Because levels rise after a dose and ease down before the next one, clinicians recheck blood levels about 30 days after you start, then keep monitoring. Your provider may also check hemoglobin, hematocrit (the share of blood made of red cells), and PSA, a prostate-related marker.
Frequently Asked Questions
Where Are Testosterone Injections Given?
Intramuscular injections go into a muscle, and the cypionate label specifies the buttock. Subcutaneous versions go just under the skin. Your clinician explains the technique and whether in-office or at-home use fits your plan.
How Often Are Testosterone Injections Given?
Cleveland Clinic lists intramuscular injections about every one to two weeks and subcutaneous injections weekly, with some long-acting versions about every ten weeks. The label for cypionate describes dosing every two to four weeks.
Why Is Blood Work Part of Treatment?
Blood tests confirm low testosterone before treatment and track levels afterward. They also check red blood cell counts and PSA, because testosterone therapy can raise both, so monitoring helps your clinician adjust or pause treatment.
Is Testosterone Therapy Meant for Everyone With Low Energy?
No. It is approved for men with low testosterone caused by a diagnosed medical condition. Low energy has many possible causes, so a clinician evaluates your symptoms and labs before recommending any treatment.
Good to Know
Possible side effects include acne or oily skin, ankle swelling, breast enlargement or tenderness, worsening sleep apnea (breathing pauses during sleep), smaller testicles, lower sperm count, and thicker blood from higher red cell counts. Talk with a clinician first if you have prostate or breast cancer, heart failure, a recent heart attack or stroke, or plans for biological children.
Take the Next Step With a Licensed Clinician
Wondering whether testosterone therapy could fit your situation? Start with an online assessment. An independent licensed clinician reviews your health history and symptoms, orders appropriate lab work, and when a prescription is appropriate, a licensed pharmacy delivers it to your door. You set the pace for each next step.
This article is for education only and is not medical advice.