Testosterone Testing Before Starting Testosterone Shots
Testosterone levels must be measured on two separate mornings before starting testosterone injections, with no specific minimum number of days required between the diagnosis and treatment initiation—the key is confirming persistent hypogonadism with repeat testing, not waiting a predetermined interval. 1, 2
Diagnostic Testing Timeline
The diagnostic process requires:
- Two separate fasting morning testosterone measurements (drawn between 8-10 AM) to confirm persistently low levels (<300 ng/dL), as single measurements are insufficient due to assay variability and diurnal fluctuation 1, 2, 3
- No mandated waiting period exists between the confirmatory tests and treatment initiation once hypogonadism is biochemically confirmed and symptoms are present 1, 4
- Repeat testing should occur on a different day from the initial measurement, but guidelines do not specify a minimum interval between the two tests 2, 5
Complete Pre-Treatment Workup
Before starting testosterone shots, the following must be obtained:
- Measure LH and FSH levels after confirming low testosterone to distinguish primary (testicular) from secondary (pituitary-hypothalamic) hypogonadism, as this has critical treatment implications for fertility preservation 1, 2
- Free testosterone by equilibrium dialysis should be measured in men with borderline total testosterone or conditions affecting sex hormone-binding globulin 1, 2
- Baseline hematocrit or hemoglobin must be documented, as hematocrit >54% is an absolute contraindication to starting therapy 1, 2
- PSA level and digital rectal examination in men over 40 years, with PSA >4.0 ng/mL requiring urologic evaluation before initiating therapy 1
Critical Fertility Consideration
If the patient desires fertility in the near term, testosterone therapy is absolutely contraindicated—gonadotropin therapy (hCG plus FSH) must be used instead, as exogenous testosterone suppresses spermatogenesis and causes prolonged azoospermia 1, 2, 3
Common Clinical Pitfall
The most critical error is starting testosterone without confirming the patient does not desire fertility, as this causes irreversible suppression of sperm production that may persist for months to years after discontinuation 1. Approximately 20-30% of men receiving testosterone in the United States do not have documented low testosterone levels before treatment initiation, violating evidence-based guidelines 1.
Post-Initiation Monitoring
Once treatment begins with intramuscular testosterone cypionate or enanthate (typically 100-200 mg every 2 weeks):
- First testosterone level check occurs 2-3 months after treatment initiation or any dose change, measured midway between injections (days 5-7), targeting mid-normal values of 500-600 ng/dL 1, 4, 2
- Peak serum levels occur 2-5 days after injection, with return to baseline by days 10-14, explaining the "roller coaster" effect some patients experience 6, 1
- Once stable levels are achieved, monitoring every 6-12 months is typically sufficient 1, 4