Is 1 mL of Testosterone Safe for Deltoid Injection?
Yes, 1 mL of testosterone is safe to administer in the deltoid muscle for intramuscular injection, though the FDA-approved label specifically recommends deep gluteal muscle injection as the preferred site. 1
FDA-Approved Administration Guidelines
- The FDA label for testosterone cypionate explicitly states "intramuscular injections should be given deep in the gluteal muscle" as the standard route of administration 1
- The approved dosage range is 50-400 mg every 2-4 weeks for hypogonadal males, which typically corresponds to 0.25-2 mL volume depending on concentration 1
- No specific contraindication exists for deltoid administration in the FDA labeling, though gluteal injection is the documented preferred site 1
Clinical Practice Considerations
Volume and injection site selection:
- A 1 mL volume falls well within the acceptable range for deltoid intramuscular injection from a technical standpoint, as the deltoid can accommodate up to 2 mL in most adult males 2
- The most common formulations (testosterone cypionate or enanthate) are typically 200 mg/mL concentration, meaning 1 mL delivers 200 mg—a standard replacement dose 3, 1
- Intramuscular testosterone injections are administered every 2-3 weeks, with peak serum levels occurring 2-5 days after injection 3
Practical advantages of deltoid vs. gluteal injection:
- Deltoid injection allows for self-administration, which improves patient autonomy and reduces healthcare visit requirements 3
- The gluteal site, while FDA-recommended, often requires assistance from another person for proper administration 4
- Patient preference studies show that convenience and ease of self-administration are major factors in treatment adherence 5, 3
Alternative Injection Routes
Subcutaneous administration as an emerging option:
- Recent evidence demonstrates that subcutaneous testosterone injections (typically 50-150 mg weekly) are effective and safe, achieving normal male testosterone levels across a wide BMI range (19.0-49.9 kg/m²) 4
- Among 22 patients who switched from intramuscular to subcutaneous, all had mild (n=2) or marked (n=20) preference for subcutaneous injections, with none preferring intramuscular 4
- Subcutaneous injections involve significantly less discomfort and allow easier self-administration 4
Monitoring Requirements
- Testosterone levels should be measured midway between injections (days 5-7 after injection for cypionate/enanthate), targeting mid-normal values of 500-600 ng/dL 3
- Monitor hematocrit periodically and withhold treatment if >54%, as intramuscular testosterone carries higher erythrocytosis risk compared to transdermal preparations 3, 6
- Check PSA in men over 40 years before initiating therapy and monitor for significant increases during treatment 3
Common Pitfalls to Avoid
- Never inject intravenously—testosterone cypionate is for intramuscular or subcutaneous use only 1
- Avoid injecting cold solution, as crystals may have formed during storage; warming and shaking the vial should redissolve any crystals 1
- Do not use testosterone therapy in men actively seeking fertility, as it suppresses spermatogenesis and causes azoospermia—gonadotropin therapy is mandatory instead 3
- Ensure confirmed biochemical hypogonadism (morning total testosterone <300 ng/dL on two separate occasions) before initiating therapy 3