Is a regimen of testosterone cypionate (intramuscular injection) 200mg/ml, 0.5ml once a week, appropriate for testosterone replacement therapy (TRT)?

Testosterone Cypionate 100mg Weekly is an Appropriate and Evidence-Based TRT Regimen

A regimen of testosterone cypionate 200mg/ml concentration, 0.5ml (100mg) administered intramuscularly once weekly is an appropriate and guideline-concordant approach for testosterone replacement therapy. This dosing falls within the recommended range and provides more stable testosterone levels compared to less frequent administration.

Dosing Rationale

Weekly dosing of 50-100mg testosterone cypionate or enanthate is explicitly recommended by the American College of Gastroenterology as a standard starting regimen for TRT. 1 Your prescribed dose of 100mg weekly is at the upper end of this range and appropriate for most hypogonadal men. 1

Advantages of Weekly Administration

• Weekly injections provide more stable serum testosterone levels compared to biweekly dosing, which is associated with significant fluctuations between supraphysiologic peaks and subtherapeutic troughs. 1
• The FDA-approved dosing range for testosterone cypionate is 50-400mg every 2-4 weeks, meaning your 100mg weekly regimen (equivalent to 200mg biweekly) falls well within approved parameters. 2
• More stable testosterone levels achieved through weekly dosing reduce adverse effects including erythrocytosis and potentially cardiovascular risk. 1

Administration Technique

• The injection should be given deep intramuscularly, either in the anterolateral thigh (self-administered) or gluteal muscle (administered by another person). 1
• Use an 18-gauge needle for drawing from the vial and a 21-23 gauge, 1-1.5 inch needle for injection. 1
• Longer needles (1.5 inch) are needed for gluteal injections, while 1-inch needles may suffice for thigh injections in leaner patients. 1

Monitoring Requirements

Testosterone levels must be measured 2-3 months after initiating therapy or any dose change, with levels checked midway between injections (approximately 3-4 days after injection for weekly dosing). 1, 3

Target Levels and Follow-up Schedule

• Target mid-normal testosterone values of 450-600 ng/dL (or 500-600 ng/dL per some guidelines). 4, 1
• Once stable levels are confirmed, monitoring every 6-12 months is sufficient. 1
• At each visit, assess hematocrit/hemoglobin, PSA, and perform digital rectal examination. 4

Critical Safety Monitoring

Hematocrit monitoring is essential as erythrocytosis occurs more frequently with injectable testosterone. 1 If hematocrit rises above 54%, temporarily withhold therapy, reduce dosage, or perform phlebotomy. 4

For PSA monitoring, perform prostate biopsy if:

• PSA rises above 4.0 ng/mL 4
• PSA increases by 1.0 ng/mL or more in any 12-month period 4
• PSA increases by 0.7-0.9 ng/mL in one year (repeat in 3-6 months and biopsy if further increase) 4

Common Pitfalls to Avoid

• Do not measure testosterone levels at random times—for weekly injections, measure midway between doses to avoid misinterpreting peak or trough values. 1
• Injectable testosterone may carry greater cardiovascular risk compared to transdermal preparations, possibly due to fluctuating levels with less frequent dosing, though weekly administration minimizes this concern. 4, 1
• Ensure proper sharps disposal from the start of therapy. 1
• Do not use testosterone therapy in men actively seeking fertility—it suppresses gonadotropins and severely compromises spermatogenesis. 4

Contraindications

Absolute contraindications include:

• Active male breast cancer 4
• Men actively seeking fertility (use gonadotropins instead) 4
• Severe untreated sleep apnea (relative contraindication requiring caution) 4

Dose Adjustment Strategy

• If clinical response is suboptimal and testosterone levels remain in the low-normal range despite 100mg weekly, increase to 125-150mg weekly (0.625-0.75ml of 200mg/ml concentration). 4
• If adequate clinical response occurs even with low-normal levels, no dose adjustment is needed. 4
• Maximum recommended dose for weekly administration is typically 150mg. 1