Which muscle groups are used for intramuscular testosterone hormone replacement injections?

Intramuscular Injection Sites for Testosterone

Testosterone cypionate and enanthate should be injected deep into the gluteal muscle as the primary site, with the anterolateral thigh as an acceptable alternative for self-administration. 1

FDA-Approved Primary Site

• The gluteal muscle is the FDA-labeled standard site for intramuscular testosterone cypionate injection, requiring deep intramuscular administration. 1
• The gluteal site can accommodate volumes up to 3 mL per injection, which covers the typical testosterone dosing range of 50–400 mg every 2–4 weeks. 2, 3
• A 1–1.5 inch, 22–25 gauge needle is required for proper gluteal injection to ensure the medication reaches deep muscle tissue rather than subcutaneous fat. 3

Self-Administration Alternative

• The anterolateral thigh (vastus lateralis) is the recommended site when patients self-inject, as it is easily accessible and allows patients to visualize the injection site. 3
• Thigh injections may use a 1-inch needle in leaner patients, though 1.5-inch needles remain standard for most adults to ensure intramuscular delivery. 3
• Both testosterone cypionate and enanthate can be self-administered into the thigh with 50–100 mg weekly or 100–200 mg every 2 weeks. 3

Sites to Avoid for Standard IM Testosterone

• The deltoid muscle is NOT recommended for standard testosterone injection volumes (typically 0.5–1 mL or more), as this site is reserved for smaller injection volumes (≤1 mL) and was only studied in older research without current guideline support. 3
• The deltoid was evaluated in a 1995 study of testosterone enanthate but showed higher rates of pain and bleeding compared to gluteal injections, and is not mentioned in contemporary clinical guidelines as a preferred site. 4, 3
• The abdomen and upper arm are not appropriate sites for intramuscular testosterone injections; these are reserved for subcutaneous medications like insulin. 3

Injection Technique Considerations

• Aspiration before injection is recommended—if blood appears in the needle hub, withdraw the needle and select a new site to avoid intravascular injection. 3
• When multiple injections are required in the same limb, separate injection sites by at least 1 inch to allow differentiation of any local reactions. 3
• The injection should be given deep into the muscle to ensure proper absorption and minimize local side effects. 1

Subcutaneous Alternative (Off-Label)

• Subcutaneous injection is an increasingly used off-label alternative that achieves therapeutic testosterone levels equivalent to intramuscular administration with doses of 50–150 mg weekly. 5, 6
• Subcutaneous administration is easier to self-administer, less painful, and associated with fewer local reactions than intramuscular injections, with all patients in one study preferring subcutaneous over intramuscular delivery. 5, 6, 7
• Common subcutaneous sites include the abdomen and thigh, using a shorter needle (typically 0.5 mL insulin syringe). 7
• While not FDA-approved, subcutaneous testosterone is effective across a wide BMI range (19.0–49.9 kg/m²) and produces serum levels within the normal male range in 100% of patients. 6, 7

Common Pitfalls

• Do not inject into the deltoid for standard testosterone volumes, as this site cannot safely accommodate the typical 0.5–1+ mL injection volumes and has higher complication rates. 4, 3
• Do not use needles shorter than 1 inch for gluteal injections in most adults, as inadequate needle length results in subcutaneous rather than intramuscular delivery. 3
• Patients with gluteal implants or fillers should avoid gluteal injections, as these may interfere with proper medication delivery. 3