What is the dosage of testosterone in milligrams per 0.5ml injection for a 50-year-old male patient with hypogonadism receiving injectable testosterone replacement therapy?

Testosterone Dosage Calculation for 0.5mL Injection

For a 50-year-old male with hypogonadism receiving injectable testosterone cypionate or enanthate, 0.5mL delivers 100mg of testosterone, as standard formulations contain 200mg/mL. 1

Standard Concentration and Dosing

• Injectable testosterone cypionate and enanthate are supplied at a concentration of 200mg/mL 1
• Therefore, 0.5mL = 100mg of testosterone 1
• The FDA-approved dosage range for hypogonadism is 50-400mg administered every 2-4 weeks 1

Recommended Dosing Regimens

Weekly dosing of 50-100mg (0.25-0.5mL) provides more stable testosterone levels compared to biweekly administration and is the preferred approach. 2

Primary Dosing Options:

• 100mg (0.5mL) weekly - provides optimal stability with mid-normal testosterone levels 2, 3
• 200mg (1.0mL) every 2 weeks - traditional dosing with acceptable efficacy 2, 1, 3
• 50mg (0.25mL) weekly - appropriate for initial dosing or patients requiring lower doses 2

Clinical Rationale for Dose Selection

• The 100mg weekly regimen (0.5mL) suppressed elevated LH to normal and maintained eugonadal testosterone levels throughout the dosing interval 3
• Studies demonstrate that 200mg every 10-14 days maintains eugonadal testosterone and estradiol levels through day 11 post-injection 4
• Peak serum levels occur 2-5 days after injection, with return to baseline by days 10-14, supporting more frequent dosing intervals 2, 5

Monitoring and Titration

• Testosterone levels should be measured 2-3 months after treatment initiation or any dose change, targeting mid-normal values of 450-600 ng/dL 2, 5
• For injectable formulations, measure levels midway between injections (days 5-7 for weekly dosing) 2, 5
• Once stable levels are achieved, monitor every 6-12 months 2, 5

Safety Considerations

Injectable testosterone carries greater risk of erythrocytosis (43.8%) compared to transdermal preparations (15.4%) due to fluctuating testosterone levels. 2, 5

Critical Monitoring Parameters:

• Hematocrit at each visit - withhold treatment if >54% and consider phlebotomy 2, 5
• PSA levels in men over 40 years - refer for urologic evaluation if increases >1.0 ng/mL in first 6 months or >0.4 ng/mL per year thereafter 2, 5
• Digital rectal examination to assess for prostate abnormalities 2, 5

Common Pitfalls to Avoid

• Do not use biweekly dosing (200mg every 2 weeks) as first-line - weekly dosing reduces adverse effects including erythrocytosis and provides more stable levels 2
• Do not draw testosterone levels at peak (days 2-5) - this shows supraphysiologic levels and may lead to inappropriate dose reduction 5
• Do not continue current dose if testosterone levels exceed 1000 ng/dL - supraphysiological levels increase risk of erythrocytosis 2
• Do not initiate therapy without confirming fertility desires - testosterone causes azoospermia and is absolutely contraindicated in men seeking fertility preservation 2, 5

Expected Treatment Outcomes

• Small but significant improvements in sexual function and libido (standardized mean difference 0.35) 2, 5
• Improvements in fasting glucose, insulin resistance, and lipid profiles 5
• Little to no effect on physical functioning, energy, vitality, or cognition 2, 5