Testosterone is a prescription medication classified as a Schedule III controlled substance in the United States, meaning you need a doctor’s oversight to obtain and use it. It comes in several forms: injections, topical gels, patches, nasal gels, and implantable pellets. The right method depends on your lifestyle, comfort with needles, and how your body responds. Here’s what each option looks like in practice and what to expect once you start.
Who Qualifies for Testosterone Therapy
A clinical diagnosis of low testosterone requires two separate blood draws showing a total testosterone level below 300 ng/dL, both taken in the early morning when levels are naturally highest. Low numbers alone aren’t enough. You also need symptoms: persistent fatigue, reduced sex drive, difficulty with erections, loss of muscle mass, or mood changes. If your levels are low but you feel fine, most guidelines don’t recommend treatment.
Certain conditions rule out testosterone therapy entirely. Men with untreated prostate cancer or breast cancer should not use it. The same applies to high-risk individuals, including those with a first-degree relative who had prostate cancer and African-American men with a PSA above 3 ng/mL. If your hematocrit (a measure of red blood cell concentration) is already above 54%, therapy needs to wait until that number comes down.
Injections: The Most Common Method
Injectable testosterone cypionate and enanthate are the most widely prescribed forms. The FDA-approved dosing range for cypionate is 50 to 400 mg every two to four weeks, delivered as a deep intramuscular injection into the gluteal muscle. Many prescribers start on the lower end and adjust based on follow-up bloodwork. Cypionate produces peak levels about four to five days after injection, while enanthate peaks faster, around 36 to 48 hours.
A longer-acting option, testosterone undecanoate, peaks around day seven and is injected less frequently, though it’s typically administered in a clinical setting rather than at home.
Intramuscular vs. Subcutaneous Injections
Traditional intramuscular (IM) injections go deep into a large muscle, usually the glute or thigh. Subcutaneous (SubQ) injections are shallower, depositing testosterone into the fat layer just beneath the skin. SubQ injections use a smaller needle, typically a 25-gauge, 5/8-inch needle, and target the abdomen (about 3 to 5 cm to the side of the belly button) or the thigh. Many patients find SubQ injections less painful and easier to self-administer. A locking syringe is recommended because the oil-based solution is thick enough that a standard needle could separate from the barrel during injection.
Some men on injectable testosterone split their total dose into smaller, more frequent injections (twice weekly instead of every two weeks) to keep blood levels steadier and reduce the energy and mood swings that come with large peaks and troughs. Your prescriber can help you determine if this approach makes sense for your situation.
Topical Gels and Solutions
Testosterone gel is applied daily and absorbs through the skin over several hours. Depending on the formulation, blood levels peak anywhere from 2 to 24 hours after application. Some gels absorb continuously over the full day, keeping levels relatively stable.
Application technique matters. Apply the gel only to areas a short-sleeve T-shirt would cover: your shoulders, upper arms, or abdomen. Never apply it to the genitals. After applying, wash your hands thoroughly with soap and water. Let the gel dry for a few minutes before putting on a shirt, and keep the area covered with clothing until you’ve washed it off or showered.
The biggest practical concern with gels is accidental transfer. If a woman or child touches the application area before it’s been washed, they can absorb testosterone through their own skin, which can cause serious hormonal effects. If you expect skin-to-skin contact with another person, wash the application area with soap and water first. If accidental contact happens, the exposed person should wash the area immediately.
Patches, Nasal Gels, and Pellets
Transdermal patches are applied daily, usually to the back, abdomen, upper arm, or thigh. They deliver a steady dose and reach peak levels about eight hours after application. Skin irritation at the patch site is the most common complaint.
Nasal gel is applied inside the nostrils, typically three times a day. It peaks in about 40 minutes, making it the fastest-absorbing option. The upside is zero risk of skin transfer to others. The downside is the frequency: three applications daily can be inconvenient.
Subdermal pellets are implanted under the skin in a quick office procedure and release testosterone slowly over several months, peaking at about one month. They’re low-maintenance once placed but require a minor procedure each time they need replacing.
When You’ll Start Feeling Results
Testosterone therapy doesn’t produce overnight changes. The timeline varies by symptom, and knowing what to expect helps you avoid frustration or premature dose changes.
Sexual interest is one of the first things to improve, often within three weeks, and it typically plateaus by six weeks. Morning erections also tend to return around the three-week mark. Improvements in erectile function and overall sexual satisfaction can take three to six months to fully develop, and in some cases up to a year.
Body composition changes take longer. Shifts in fat mass and lean muscle become measurable at 12 to 16 weeks. Muscle strength improvements show up in a similar window and stabilize between 6 and 12 months, with small gains continuing beyond that. If you’re expecting visible changes in the mirror, give it at least three to four months of consistent therapy combined with regular exercise.
Blood Work and Ongoing Monitoring
Starting testosterone isn’t a one-time decision. It requires regular lab work, especially in the early months while your dose is being dialed in.
Your total testosterone level should be checked two to four weeks after starting therapy, depending on the formulation. Once your dose is stable, that blood draw shifts to every 6 to 12 months. The goal is to bring your levels into the normal range without overshooting.
Hematocrit is the other critical number. Testosterone stimulates red blood cell production, and too many red blood cells thicken the blood and raise the risk of clots. Intramuscular injections cause the largest hematocrit increase, averaging about 4%. Patches and nasal gels produce much smaller changes. Your hematocrit should stay below 54%. If it rises above 52%, your doctor may reduce your dose, switch your delivery method, or recommend a therapeutic blood draw to bring levels down. This value is checked every 6 to 12 months once you’re stable.
PSA, the prostate screening marker, tends to rise modestly on testosterone therapy, averaging about 0.30 ng/mL. Older men see a slightly larger increase. Whether and how often to test PSA is a shared decision between you and your doctor, guided by your age and risk factors.
Common Side Effects
Acne is one of the most frequent side effects, caused by increased oil production in the skin. It’s usually manageable with standard skincare but can be persistent.
Testosterone converts partially to estrogen in the body. When estrogen levels climb above about 60 pg/mL, some men develop breast tenderness or breast tissue growth (gynecomastia). This is treatable if it occurs, and your doctor can check estrogen levels if you notice breast symptoms.
Sleep apnea can worsen on testosterone therapy. If you develop loud snoring, gasping during sleep, or excessive daytime sleepiness, bring it up at your next appointment.
Blood pressure may increase, which is another reason regular monitoring matters. Older oral formulations of testosterone carried a risk of liver toxicity, but current injectable, transdermal, and newer oral forms have a significantly lower risk.
Fertility Considerations
Testosterone therapy suppresses your body’s own hormone signals that drive sperm production. For most men on TRT, sperm counts drop significantly, and some become temporarily infertile. If you’re planning to have children, this is a conversation to have with your doctor before starting therapy. Alternative treatments exist that can raise testosterone levels while preserving fertility. If you’re already on testosterone and fertility becomes a priority, your doctor may check follicle-stimulating hormone (FSH) levels to assess where things stand.