What is the recommended frequency for checking testosterone levels and other labs in a trans person on testosterone supplements?

Testosterone and Laboratory Monitoring in Transgender Individuals on Testosterone Therapy

Direct Recommendation

For transgender individuals starting testosterone therapy, measure testosterone levels at 2-3 months after initiation or any dose change, then every 3-6 months during the first year, and every 6-12 months thereafter once stable therapeutic levels are achieved. 1, 2

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Initial Monitoring Phase (First Year)

Testosterone Level Timing

• Check testosterone at 2-3 months after starting therapy or making any dose adjustments to assess treatment efficacy and determine if dose modifications are needed 1
• Continue monitoring every 3-6 months throughout the first year 1, 3
• Most laboratory values reach stable levels within 6 months (particularly red blood cell indices and creatinine) 4

Critical Blood Draw Timing

• 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 5, 1
• For all formulations: Morning timing is essential due to diurnal variation 2

Target Testosterone Levels

• Goal: 300-1,000 ng/dL (male physiological range) 3
• More specifically, aim for 450-600 ng/dL (middle tertile of normal range) 1, 2
• In one study, mean levels after 18 months were approximately 545 ng/dL 6

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Maintenance Monitoring (After First Year)

Testosterone Monitoring Frequency

• Every 6-12 months once stable therapeutic levels are achieved 1, 2, 3
• This ensures maintenance of therapeutic levels and early detection of supraphysiologic levels that could increase adverse event risk 1, 2

When to Discontinue Therapy

• Stop testosterone if target levels are achieved without symptom improvement after 3-6 months 1, 2

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Additional Laboratory Monitoring

Complete Blood Count

• Hemoglobin/hematocrit monitoring is mandatory at each visit to detect erythrocytosis 5, 1
• Red blood cell indices stabilize within 6 months and remain stable long-term 4
• Hemoglobin increases by approximately +1.72 g/dL and hematocrit by +4.76% 4, 6
• Polycythemia risk is significant (up to 46.67% in some testosterone formulations) 7
• If hematocrit rises above reference range, consider temporarily withholding therapy, reducing dose, or performing phlebotomy 5

Metabolic Panel

• Monitor electrolytes, renal function, and liver enzymes 4
• Creatinine levels shift toward affirmed gender reference ranges after 1 year of therapy 5
• For individuals on testosterone >1 year: Interpret creatinine and most lab values based on affirmed gender (male) reference ranges 5
• For those <1 year on therapy: Values are transitioning; interpret with caution 5
• Aspartate transaminase may increase modestly (+4.3 U/L) 6
• Blood glucose typically decreases slightly (-5.33 mg/dL) 6

Lipid Panel

• Monitor lipids regularly as testosterone therapy affects lipid metabolism 4, 6
• LDL and triglycerides may increase beyond the first year 4, 8
• HDL may decrease beyond the first year 4
• One study showed no significant lipid changes, while others demonstrated mild cholesterol and triglyceride elevations 6, 8

Body Composition

• Track body mass index at each visit 6
• Expect approximately 4 kg increase in lean body mass after 1 year on testosterone 5
• BMI typically increases by approximately +1.23 kg/m² 6

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Long-Term Considerations

Laboratory Values Beyond First Year

• Some analytes continue to change beyond 1 year: LDL, HDL, and liver enzymes may show ongoing trends 4
• Maximum virilization effects are usually achieved after 3-5 years of regular testosterone use 3

After Discontinuation

• If testosterone is stopped, laboratory values typically return to baseline within 10 weeks (approximately 3 months) 5, 4
• After 3 months off therapy, interpret lab values based on sex assigned at birth 5

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Common Pitfalls to Avoid

Timing Errors

• Never measure testosterone at random times: Injectable testosterone requires midway measurement between doses; morning measurement is essential for all formulations 1
• Failure to account for peak/trough variations with injectable formulations leads to inappropriate dose adjustments 5, 1

Reference Range Misinterpretation

• After 1 year on testosterone, use male reference ranges for most laboratory values, particularly creatinine and hemoglobin 5
• During the first year, recognize that values are transitioning and may not fit either male or female reference ranges cleanly 5

Inadequate Hematocrit Monitoring

• Polycythemia is a significant risk and requires vigilant monitoring at every visit 5, 1, 7
• This is particularly important with certain formulations like testosterone pellets 7

Premature Dose Escalation

• If clinical response is adequate, no dose adjustment is needed even if levels are in the low-normal range 5
• Only increase dose if clinical response is suboptimal AND testosterone levels are low-normal or below 5