Short answer: Testosterone cypionate and enanthate vials are labeled for intramuscular use: the Depo-Testosterone label says to give the shot "deep in the gluteal muscle", and the enanthate label says to inject it slowly into the gluteal muscle and avoid injecting into a vein. Patient guides add the steps: clean hands and skin, a new needle and syringe, a 90-degree angle, and a sharps container afterwards. Your prescriber or nurse should show you the site before you inject at home.
The Depo-Testosterone (testosterone cypionate) label says the injection is "for intramuscular use only", should not be given into a vein, and "should be given deep in the gluteal muscle". It also says that warming and shaking the vial should redissolve crystals that can form if the vial was stored too cold.
The testosterone enanthate label says to take care "to slowly inject the preparation deeply into the gluteal muscle" and to follow the usual precautions for intramuscular shots, "such as the avoidance of intravascular injection". It reports rare post-marketing cases of an urge to cough, coughing fits and trouble breathing right after an injection of this oil-based product. It also notes that a wet needle or syringe can make the solution cloudy without changing its strength.
Not every testosterone injection goes into muscle. Xyosted, a testosterone enanthate autoinjector, is labeled for injection under the skin of the belly only, and its label says to avoid intramuscular injection. Aveed (testosterone undecanoate) carries a boxed warning for oil microembolism (POME) and allergic reactions and is given only in a clinic, with 30 minutes of observation after each shot.
MedlinePlus, the patient site of the US National Library of Medicine, describes four sites for an intramuscular (IM) shot:
A 2023 systematic review of 17 studies (1,429 people) found that shots in the hip site caused less pain, bleeding and bruising than shots in the upper outer buttock. The labels for cypionate and enanthate name the gluteal muscle; whether another muscle suits you is a question for your prescriber.
If you give more than one shot, MedlinePlus says not to use the same spot twice in a row. Use the other side or another site.
Pulling back to check for blood before injecting is called aspiration. CDC says it is not needed for vaccines, because no large blood vessels sit at the recommended vaccine sites. A 2015 systematic review reached the same view for the deltoid, hip and thigh sites, but recommended aspirating at the upper outer buttock because of the nearby gluteal artery. The testosterone labels do not mention aspiration; they ask you to avoid injecting into a blood vessel. Ask the person who trains you which method they want you to use.
MedlinePlus says to call emergency services for a rash, strong itching, trouble breathing, or swelling of the mouth, lips or face after an injection, and to contact your provider about fever or a lump, bruise or swelling that does not go away. The enanthate label lists coughing right after the shot as a rare reaction to report.
Writing down the date, the site and the side after each shot makes it easier to rotate sites and to spot a pattern if one site keeps getting sore. Dose Track saves the site with each logged dose.
Read more on Dose Track: Intramuscular injection (glossary) · Testosterone cypionate guide · Depo-Testosterone dosing schedule · Subcutaneous vs intramuscular testosterone · Injection site rotation · How to store Depo-Testosterone