How to inject Testosterone
Published September 21, 2026 · 13 min read
This guide is for men who already have a testosterone prescription and are injecting at home. Your prescriber sets three things: the dose, the concentration of the vial, and the frequency. Nothing here changes any of those. What follows is the part nobody spends enough time on — where the needle goes, what size it should be, and how to do it without the lump, the bleed or the ache that makes men dread week two.
The short version. Most men on weekly or twice-weekly testosterone cypionate inject subcutaneously into abdominal fat with a short half-inch 27 to 30 gauge needle, or intramuscularly into the outer thigh or the side of the hip with a one to one-and-a-half inch 23 to 25 gauge needle. Draw with a wide needle, inject with a narrow one, rotate sites every time, and warm the vial in your hand first.
Where to inject testosterone
Four sites are worth using. Two of them you can reach comfortably yourself; two are better with help or with practice.
Abdomen
The default for most menVastus lateralis (outer thigh)
Easiest IM site to self-injectVentrogluteal (side of hip)
Least painful IM siteDeltoid (shoulder)
Small volumes onlyFinding the ventrogluteal site
This is the site most men have never been shown and the one experienced injectors tend to settle on, because it has the thickest muscle and no large nerves running through it.
Put the palm of your opposite hand on the bony knob at the top of your thigh — right hand on left hip. Point your index finger at the front point of your hip bone and spread your middle finger back along the ridge of the pelvis. The V between those two fingers is the target. Inject in the middle of it, straight in.
Finding the vastus lateralis
Sit down. Divide the front of your thigh into thirds from hip to knee. The middle third, on the outer side — roughly a hand's width above the knee and a hand's width below the hip — is the target. You can feel the muscle firm up if you lift your foot off the floor.
Where not to inject testosterone
Avoid these. The upper outer buttock — the old "dorsogluteal" site — sits near the sciatic nerve, and it is why the ventrogluteal site replaced it in modern practice. Anywhere with a mole, a scar, a tattoo, a bruise, a rash or broken skin. Any site that is still sore, hard or lumpy from a previous injection. Directly into a visible vein. And never into the same spot twice in a row.
Subcutaneous or intramuscular?
Both work. The evidence over the last decade has moved steadily toward subcutaneous for routine TRT, and most men who switch do not go back.
Subcutaneous
Intramuscular
If you are injecting more than about a millilitre at a time, intramuscular is the practical choice — subcutaneous tissue does not absorb large volumes comfortably. If your dose is small and split across the week, subcutaneous is easier on you and produces steadier levels. Your prescriber decides which route your prescription is written for; ask if you want to change.
What you need
Why two needles
This is the single change that makes the biggest difference to comfort, and most men are never told it.
Testosterone is suspended in oil. It is thick, and pulling it through a fine needle is slow and frustrating. So you draw with a wide needle — 18 or 21 gauge — which fills the syringe in seconds. But pushing a needle through a rubber vial stopper blunts the tip, and a blunted wide needle is exactly what makes an injection hurt.
So you swap. Draw with the wide one, take it off, put a fresh narrow one on, and inject with that. Two needles per injection, one sharp tip going into you.
Needle size, in plain terms
Gauge runs backwards: the higher the number, the thinner the needle. A 30G is finer than a 23G. Length matters separately — a subcutaneous injection needs to reach fat and stop, so half an inch; an intramuscular injection needs to get past fat into muscle, so an inch or more depending on your build.
How to inject: subcutaneous
How to inject: intramuscular
Steps one to seven are identical. From there:
Rotating sites
Injecting into the same square inch week after week builds scar tissue. Scarred tissue absorbs unevenly, hurts more, and eventually gives you a hard lump that takes months to resolve.
Rotation is simple if you make it mechanical rather than remembering. Subcutaneous: left of the navel, then right, then left again, moving an inch or two each time so you are working around a clock face over a couple of months. Intramuscular: left hip, right hip, left thigh, right thigh, and back to the start — four weeks before any site repeats.
Write the site on a calendar or in your phone. Everyone believes they will remember. Nobody does.
If something goes wrong
It bled afterwards. Small nicked vessel. Press for a minute, use a plaster. Normal and not a problem.
A bruise came up. Also common, especially subcutaneously. It will clear. Press rather than rub next time.
A small lump under the skin. Usually oil that has not dispersed yet, or the result of rubbing the site. A warm compress helps. If it is hard, hot, red or growing, that is different — see below.
It aches the next day. Very common intramuscularly, especially in a new site. Injecting more slowly, warming the vial first, and walking afterwards all reduce it.
A drop leaked out. Harmless. Press a little longer next time, or leave the needle in for a couple of seconds before withdrawing.
It stung going in. Usually wet alcohol, a cold vial, or a blunted needle because the draw needle was reused to inject.
Contact a clinician the same day if the site becomes hot, hard, red and spreading, if you develop a fever, if pain worsens over several days rather than settling, or if you get chest tightness, breathlessness or coughing shortly after an injection.
Frequently asked questions
Where is the best place to inject testosterone? For most men, subcutaneously into abdominal fat — easiest to see, least painful, and steady absorption. For intramuscular injections, the ventrogluteal site on the side of the hip has the thickest muscle and no major nerves nearby.
Is it better to inject testosterone into fat or muscle? Both are effective. Subcutaneous injection into fat is less painful, uses a much finer needle and produces flatter hormone levels. Intramuscular absorbs faster and handles larger volumes. Most routine TRT at typical doses is well suited to subcutaneous.
Why is testosterone so hard to inject? It is suspended in oil, which is thick and slow through a fine needle. Warming the vial in your hands and drawing with a wide needle before switching to a narrow one for the injection itself solves most of it.
What needle size should I use? For subcutaneous, 27 to 30 gauge at half an inch. For intramuscular, 23 to 25 gauge at one to one and a half inches depending on your build. Draw with an 18 to 21 gauge needle and swap before injecting.
Is 1 mL of testosterone a week enough? That question cannot be answered in millilitres. A millilitre of a 100 mg/mL vial and a millilitre of a 200 mg/mL vial are different doses. Your prescriber sets the dose in milligrams based on your labs and your symptoms, and adjusts it after your follow-up bloods.
How often should I inject? Whatever your prescription says. Twice weekly is common because smaller, more frequent doses produce steadier levels and fewer swings in mood and energy than one large weekly dose.
Do I need to aspirate? Guidance has shifted. Aspiration was standard teaching for intramuscular injections and many clinics still teach it, while others have dropped it for the ventrogluteal and vastus lateralis sites, where large vessels are not present. Follow what your prescriber told you.
How quickly do testosterone injections work? Libido typically starts shifting around week three. Energy and mood through weeks four to eight. Body composition from around week twelve. The full timeline is here.
Goprolean prescribes injectable testosterone cypionate at $129 a month, with labs and clinician visits included and no consultation fee. A licensed physician reviews every intake before anything is dispensed.
See injectable TRT
This article is general health information for people who already hold a prescription, and is not medical advice for any individual. Always follow the dose, concentration, route and frequency your own prescriber has given you. Prescriptions are issued only after a medical intake is reviewed by a licensed physician, who may determine that treatment is not appropriate. Goprolean is the telehealth practice of Prolean Wellness, Scottsdale, Arizona. See our health-information handling, Privacy and Terms.
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