What is the correct technique for subcutaneous testosterone injection?

Subcutaneous Testosterone Injection Technique

Subcutaneous testosterone injections should be administered weekly at doses of 50-150 mg using a 27-gauge, 5/8-inch needle inserted at 90 degrees into the abdomen or thigh, with the abdomen being the preferred site for ease of self-administration and consistent absorption. 1, 2, 3

Injection Sites

Primary recommended sites:

• Abdomen: 2 adult fingerbreadths away from the umbilicus, avoiding the midline 4, 1
• Anterior lateral thigh: Upper third of the thigh 4, 1

The abdomen is generally preferred because it allows easier self-administration and provides consistent testosterone absorption across a wide BMI range (19.0-49.9 kg/m²). 3 The thigh is an acceptable alternative, particularly for patients who prefer variation in injection sites. 1

Sites to avoid:

• Upper arm and buttocks are NOT recommended for subcutaneous testosterone (these are reserved for intramuscular injections or other subcutaneous medications like insulin) 4, 1
• Areas with scars, lipohypertrophy, or skin abnormalities 4
• Within 1 cm of the umbilicus 4

Needle Specifications and Technique

Equipment:

• Needle size: 27-gauge, 5/8-inch needle (or up to 1-inch for patients with higher BMI) 5
• Drawing needle: 18-gauge for drawing from vial 1
• Syringe: 1 mL insulin syringe or 1-3 mL standard syringe 1, 6
• Injection angle: 90 degrees perpendicular to skin 4

Step-by-step technique:

1. Clean the vial top and injection site with alcohol prep pad 1
2. Draw medication using 18-gauge needle, then switch to 27-gauge for injection 1
3. For most patients, insert the needle at 90 degrees without a lifted skinfold 4
4. Skinfold technique: Only use a 2-finger lifted skinfold if the patient is very lean and the presumed skin-to-muscle distance is less than the needle length 4
5. Inject slowly and steadily
6. Apply pressure with gauze after withdrawal 1
7. Cover with adhesive bandage 1
8. Dispose of needle/syringe in sharps container 1

Dosing Protocol

Initial dosing:

• Start at 50-100 mg weekly via subcutaneous route 1, 3
• This is equivalent to 100-200 mg every 2 weeks intramuscularly 1

Dose range:

• Therapeutic range: 50-150 mg weekly subcutaneously 1, 3
• Doses are adjusted based on serum testosterone levels measured at 2-3 months 1

Target testosterone levels:

• Mid-normal range: 450-600 ng/dL 1
• Acceptable range: 300-1,000 ng/dL 1

Advantages of Subcutaneous Over Intramuscular

Clinical evidence strongly supports subcutaneous administration:

• Equivalent efficacy: Achieves therapeutic testosterone levels comparable to intramuscular injections 1, 2, 3
• More stable levels: Serum testosterone remains stable throughout the weekly dosing interval (mean 627 ± 206 ng/dL) without the peaks and troughs seen with biweekly IM injections 7
• Patient preference: In a study of 22 patients who switched from IM to SC, 20 had a marked preference and 2 had a mild preference for SC; none preferred IM 3
• Easier self-administration: Patients can self-inject with relative ease using the shorter, thinner needle 2, 3
• Less discomfort: Significantly less painful than IM injections 2, 3
• Minimal adverse effects: Only 9 out of 63 patients (14%) reported minor and transient local reactions 3

Site Rotation and Safety

Rotation protocol:

• Rotate injection sites with each administration to prevent lipohypertrophy 4
• If using the abdomen, alternate between left and right sides, staying at least 2 fingerbreadths from previous injection sites 4
• Inspect sites regularly for any tissue changes, redness, or induration 4

Common pitfalls to avoid:

• Do not use 4-mm needles designed for insulin—these are too short for testosterone injection 4
• Do not inject into the same site repeatedly—this causes lipohypertrophy and unpredictable absorption 4
• Do not aspirate before injection—this is not necessary for subcutaneous injections and may cause unnecessary discomfort
• Do not forget sharps disposal—provide patients with a sharps container from the start of therapy 1

Monitoring Requirements

Initial monitoring:

• Measure testosterone levels at 2-3 months after initiation or dose change 1
• Check levels midway between injections (approximately 3-4 days after injection for weekly dosing) 1

Ongoing monitoring:

• Testosterone levels every 6-12 months once stable 1
• Hematocrit/hemoglobin at every visit—subcutaneous testosterone still carries risk of erythrocytosis, though lower than IM (15.4% vs 43.8%) 1
• PSA and digital rectal exam for men over 40 1
• Assess for cardiovascular symptoms, though SC route may have lower cardiovascular risk than IM due to more stable levels 1

Efficacy Across Patient Populations

Proven effectiveness:

• Achieves normal male testosterone range in 100% of patients when properly dosed 3, 6
• Effective across wide BMI range (19.0-49.9 kg/m²) 3
• Produces amenorrhea in 96% of transgender men (51/53) 3
• Maintains stable free testosterone levels (mean 146 ± 51 pg/mL) throughout dosing interval 7