How to inject testosterone

A prescription testosterone injection only takes a few minutes once you know the steps — but gauge, site, and technique all affect comfort, absorption, and how much you bruise. Here is the full IM and SubQ process, start to finish.

Testosterone replacement therapy (TRT) is a prescription treatment, and the injection itself is a small procedure with real technique behind it — needle choice, site selection, and rotation all affect absorption, comfort, and how many bruises or lumps you end up with. The Endocrine Society's clinical practice guideline on testosterone therapy frames dosing and monitoring as something that happens under a clinician's supervision, not as a one-time instruction you follow forever without check-ins¹. This guide walks through both major injection routes — intramuscular (IM) and subcutaneous (SubQ) — step by step. For a deeper comparison of which route might suit you, see our SubQ vs IM testosterone guide, and for the broader picture of starting and managing therapy, visit the TRT hub.

Supplies checklist before your first injection

Gather everything before you draw up a dose — hunting for an alcohol swab mid-injection is how contamination and dropped syringes happen. A basic kit includes:

1. Your prescribed testosterone vial (cypionate or enanthate, typically 100–200 mg/mL), stored and labeled as your pharmacy directed
2. A drawing needle, usually 18–22 gauge, to pull the oil-based solution out of the vial
3. A separate injecting needle — 22–25G for IM sites, 25–27G for SubQ sites — swapped on after drawing
4. A syringe sized to your dose (commonly 1 mL or 3 mL)
5. Alcohol swabs (one for the vial top, one for the injection site)
6. A sharps container for safe needle disposal
7. Gauze or a cotton ball for after the injection

Every injection should use a needle and syringe that has never touched another person or a second vial — a single-use, single-time rule the CDC's injection safety program summarizes as "one needle, one syringe, only one time"². The World Health Organization's injection safety toolkit adds the same baseline: sterile equipment from an unopened package for every injection, and hand hygiene before you start³. These aren't hospital-only rules — they apply just as much to a self-injection at your kitchen table.

Needle sizes: the draw needle isn't the injecting needle

Testosterone cypionate and enanthate are suspended in oil, which is thicker than the saline-based solutions used for most vaccines. A wider drawing needle (18–22 gauge) pulls the oil out of the vial faster and with less plunger effort. But that same wide needle is more painful going into skin and muscle, and it can drag a small oil deposit through the surface layers on the way in. The standard practice is to draw with the wider needle, then cap it, remove it from the syringe, and attach a fresh, finer needle before injecting: 22–25 gauge for IM sites, 25–27 gauge (often 1/2 to 5/8 inch) for SubQ sites. Needle length also matters by site — StatPearls' overview of intramuscular injection technique notes that true muscle penetration depends on matching needle length to the site and the person's body composition, since an underlength needle can land in fat instead of muscle⁴.

Choosing an injection site

Intramuscular sites

The ventrogluteal site — the hip, not the classic upper-outer-buttock "dorsogluteal" spot — has become the preferred IM site in clinical nursing literature because it sits over well-developed muscle with a thinner fat layer and fewer major nerves and blood vessels nearby. A study on changing nurse practice toward the ventrogluteal site found it consistently rated as the safest available IM location, though many providers still default to the old dorsogluteal site out of habit rather than evidence⁵. The deltoid (upper arm) and vastus lateralis (outer thigh) are the other two commonly used IM sites, both reasonable for self-injection once you've been shown proper landmarks by your prescriber or nurse. For a full visual breakdown of where each site sits and how to rotate between them, see our testosterone injection sites and rotation chart.

Subcutaneous sites

SubQ testosterone goes into the fat layer, not the muscle — most people use the abdomen (a couple of inches from the navel, rotating around the belt line) or the front of the thigh. Because SubQ needles are shorter and finer, self-injection tends to be easier to learn and less intimidating for new patients, which is part of why some prescribers now default new patients to SubQ dosing. A 2017 study in transgender men found SubQ testosterone cypionate produced serum testosterone levels within the normal male range across all participants, comparable to IM dosing⁶, and a larger 2022 review concluded SubQ injection is a "safe, practical, and reasonable option" for testosterone therapy more broadly⁷. Route still changes your effective dose and injection frequency, though, so switching from IM to SubQ (or the reverse) is a conversation with your prescriber, not a DIY swap — our SubQ vs IM comparison goes deeper on what changes between the two routes.

Drawing the correct dose from a multi-dose vial

1. Wash your hands, then wipe the rubber top of the vial with an alcohol swab and let it dry
2. Draw air into the syringe equal to your prescribed dose volume, and inject that air into the vial (this prevents a vacuum that makes drawing harder)
3. Invert the vial, needle tip below the liquid line, and pull the plunger back to your prescribed volume
4. Tap the syringe gently to move any air bubbles to the top, then push them out before removing the needle from the vial
5. Cap the drawing needle and swap it for your injecting needle without touching the shaft

Testosterone cypionate is a Schedule III controlled substance labeled for intramuscular use, and its FDA prescribing information specifies that injections should be given deep into muscle tissue — never intravenously⁸. If your prescriber has specifically moved you to a SubQ protocol, that's a documented off-label or alternative-route decision your clinician has made deliberately, not something to improvise on your own the first time you're handed a vial.

Step-by-step: intramuscular injection technique

1. Locate your site (ventrogluteal, deltoid, or vastus lateralis) using the landmarks your provider showed you
2. Clean the skin with an alcohol swab in a circular motion, working outward, and let it air-dry for a few seconds
3. Hold the syringe like a dart and insert the needle at a 90-degree angle in one smooth, quick motion
4. If your prescriber has asked you to aspirate, pull back gently on the plunger for a few seconds to check for blood before injecting
5. Push the plunger slowly and steadily — roughly 5 seconds per milliliter — to reduce pressure-related pain
6. Withdraw the needle at the same angle you inserted it, then apply gentle pressure with gauze (avoid rubbing or massaging the site)
7. Dispose of the needle immediately in a sharps container

Step-by-step: subcutaneous injection technique

1. Choose an abdominal or thigh site at least an inch from your last injection spot
2. Clean the skin with an alcohol swab and let it dry
3. Pinch about an inch of skin and fat between two fingers
4. Insert the needle at a 45–90 degree angle, depending on how much tissue you're pinching and the needle length you're using
5. Release the pinch, then push the plunger slowly and steadily
6. Withdraw the needle, apply light pressure with gauze, and dispose of the needle in a sharps container

Aspirating: is it still recommended?

Aspiration — pulling back on the plunger before injecting to check whether the needle has landed in a blood vessel — used to be taught as a universal step. That has changed for most IM sites. The CDC does not recommend routine aspiration for vaccine injections, on the basis that no major blood vessels sit at the standard IM sites (deltoid, vastus lateralis, ventrogluteal)², and large observational studies of tens of thousands of injections have found essentially no cases of blood aspiration at those sites. That guidance was built around vaccines, though, not oil-based testosterone esters, and the debate hasn't fully closed — a 2022 review argued the practice deserves continued scrutiny rather than blanket abandonment, particularly given case reports of nurses still aspirating blood even at the deltoid⁹.

Rotate your injection sites

Injecting the same exact spot every time thickens the tissue underneath (a buildup sometimes called lipohypertrophy), which can slow absorption and make future injections more painful. Rotating between at least two or three sites — left hip one week, right hip the next, for example — gives tissue time to recover. Our injection sites and rotation chart walks through a simple rotation schedule and shows exactly where each landmark sits on the body.

Hygiene and sharps disposal

Wash your hands before you touch any supplies, wipe both the vial top and the injection site with fresh alcohol swabs, and never reuse a needle — even on yourself, even "just this once." A used needle dulls after a single pass through the rubber vial stopper, which makes the next injection more painful and raises infection risk. Drop every used needle and syringe straight into an FDA-cleared sharps container; when it's full, most pharmacies and local health departments offer a free take-back or mail-back program instead of household trash disposal.

Injection frequency: weekly vs. split dosing

Some protocols use one larger weekly injection; others split the same weekly total into two or more smaller doses (twice-weekly, every-other-day, or even daily microdosing) to smooth out peaks and troughs. Your prescriber sets the frequency based on your labs and how you feel across the week, not just the dose itself — a switch from weekly to split dosing usually means a smaller volume per injection, which changes needle choice too. If you want to see how a given weekly total translates into split doses, the TRT dose calculator does that math for you.

Aftercare: bleeding, bruising, and lumps

A drop of blood at the injection site is common and not a sign anything went wrong — apply light pressure with gauze for 30–60 seconds and it typically stops. Mild soreness or a small bruise over the next day or two is also normal, especially at IM sites. A firm lump that doesn't soften within a week, spreading redness, warmth, or fever are different — those can indicate infection or an injection reaction and warrant a call to your prescriber rather than a wait-and-see approach.

Common mistakes beginners make

1. Injecting too fast, which increases pressure pain and can push testosterone back out along the needle track
2. Reusing the same site every single time instead of rotating
3. Skipping the air-bubble check, leaving trapped air in the syringe
4. Using the wide drawing needle to inject instead of swapping to a finer needle
5. Massaging the site afterward, which can push medication into surrounding tissue and irritate it
6. Injecting through clothing or unclean skin to save time

When to call your doctor

Contact your prescriber for a lump that grows or doesn't resolve within a week, redness that spreads beyond the injection site, fever or chills after an injection, significant pain that doesn't ease within a day or two, or if you're unsure whether you hit muscle vs. fat and are concerned about the dose. Beyond injection-site issues, testosterone therapy needs periodic bloodwork to check levels, hematocrit, and estradiol — our TRT bloodwork guide covers what gets tested and when, which is a separate but equally important part of staying safe on therapy.

Disclaimer: this article explains general injection technique and is not medical advice. Testosterone cypionate and enanthate are prescription, Schedule III controlled medications — your dose, injection route, frequency, and any change to your protocol should come from the clinician who is monitoring your bloodwork, not from a website. If anything here conflicts with what your prescriber told you, follow your prescriber.

FAQ

References

Primary sources — PubMed / NEJM / The Lancet.

1. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. https://academic.oup.com/jcem/article/103/5/1715/4939465
2. Centers for Disease Control and Prevention. Preventing Unsafe Injection Practices. Injection Safety. https://www.cdc.gov/injection-safety/hcp/clinical-safety/index.html
3. World Health Organization. WHO Best Practices for Injections and Related Procedures Toolkit. NCBI Bookshelf. 2010. https://www.ncbi.nlm.nih.gov/books/NBK138495/
4. Polania Gutierrez JJ, Munakomi S. Intramuscular Injection. StatPearls [Internet]. 2023. https://www.ncbi.nlm.nih.gov/books/NBK556121/
5. Gürol Arslan G, Özden D. Creating a change in the use of ventrogluteal site for intramuscular injection. Patient Prefer Adherence. 2018;12:1749-1758. https://pmc.ncbi.nlm.nih.gov/articles/PMC6145361/
6. Spratt DI, Stewart II, Savage C, et al. Subcutaneous Injection of Testosterone Is an Effective and Preferred Alternative to Intramuscular Injection: Demonstration in Female-to-Male Transgender Patients. J Clin Endocrinol Metab. 2017;102(7):2349-2355. https://academic.oup.com/jcem/article/102/7/2349/3098651
7. Kaminetsky JC, Moclair B, Hemani M, et al. Testosterone Therapy With Subcutaneous Injections: A Safe, Practical, and Reasonable Option. J Clin Endocrinol Metab. 2022;107(3):614-626. https://academic.oup.com/jcem/article/107/3/614/6410585
8. DailyMed. DEPO-TESTOSTERONE (testosterone cypionate) injection, solution — Prescribing Information. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=cfbb53d4-b868-4a28-8436-f9112eb01c39
9. Herraiz-Adillo A, Martinez-Vizcaino V, Pozuelo-Carrascosa DP. Aspiration before intramuscular vaccines injection, should the debate continue? Enferm Clin (Engl Ed). 2022;32(3):190-197. https://pmc.ncbi.nlm.nih.gov/articles/PMC8783631/