When should testosterone levels be re-checked in an elderly male on testosterone therapy, and can it be done while the patient is still taking testosterone?

Testosterone Level Monitoring in Elderly Men on Testosterone Therapy

Testosterone levels should be re-checked at 2-3 months after treatment initiation or any dose change, and yes, this must be done while the patient is actively taking testosterone to assess treatment efficacy and guide dose adjustments. 1

Initial Monitoring Timeline

The critical first measurement occurs at 2-3 months after starting therapy or making any dose adjustment. 1 This timing allows assessment of whether therapeutic levels have been achieved and whether dose modifications are needed. The American College of Physicians specifically recommends measuring testosterone at both approximately 14 days and 28 days after treatment initiation to ensure proper dosing, with the dose titrated based on pre-dose morning serum testosterone concentrations. 2

Maintenance Monitoring Schedule

After the initial stabilization period:

• Monitor testosterone levels every 6-12 months while on therapy to ensure maintenance of therapeutic levels and early detection of supraphysiologic levels that could increase adverse event risk. 1
• Clinical symptom re-evaluation should occur within 12 months and periodically thereafter, with discontinuation of therapy if there is no improvement in sexual function (the primary indication for treatment in age-related low testosterone). 3

Critical Timing for Blood Draws

The timing of blood collection is crucial and depends on the formulation:

• For injectable testosterone: Measure midway between injections (typically day 5-7 for weekly injections), targeting mid-normal values. 1 Peak levels occur 2-5 days post-injection, with return to baseline by 10-14 days. 1
• For all formulations: Morning measurement is essential, as testosterone levels naturally fluctuate throughout the day. 1
• For topical preparations: Patients should avoid swimming, showering, or washing the application site for a minimum of 2 hours after application to ensure adequate absorption. 2

Target Therapeutic Levels

The goal is to achieve total testosterone in the middle tertile of the normal range (450-600 ng/dL). 1 The dose should be adjusted based on pre-dose morning serum testosterone concentrations:

• Greater than 750 ng/dL: Decrease daily dose 2
• 350-750 ng/dL: Continue current dose 2
• Less than 350 ng/dL: Increase daily dose 2

Additional Monitoring Parameters Beyond Testosterone

While monitoring testosterone levels, several other parameters require surveillance:

• PSA at each visit to detect prostate-related issues 1
• Hematocrit/hemoglobin for erythrocytosis, as testosterone therapy increases this risk 1, 4
• Symptomatic response evaluation including voiding symptoms, sleep apnea, and digital rectal examination 1

PSA-Specific Thresholds

• Perform prostate biopsy or urology referral if PSA rises above 4.0 ng/mL 1
• Consider biopsy if PSA increases by ≥1.0 ng/mL within any 12-month period 1

Common Pitfalls to Avoid

Never measure testosterone at random times during the day or injection cycle. 1 Injectable testosterone requires measurement midway between doses, and morning measurement is essential for all formulations to account for diurnal variation. 1

Do not discontinue testosterone before checking levels - the entire purpose of monitoring is to assess whether therapeutic levels are being achieved while on treatment. 1 The measurements guide dose adjustments to optimize therapy.

Avoid continuing therapy indefinitely without symptom reassessment. If target testosterone levels are achieved but symptoms do not improve after 3-6 months, therapy should be discontinued. 1, 5