Testosterone Replacement Therapy: Evidence‑Based Dosing and Monitoring Guidelines

Initial Dose Selection

For most hypogonadal men, start transdermal testosterone gel (1.62 % concentration, approximately 40 mg daily, applied to shoulders and upper arms) to achieve stable physiologic levels with a lower adverse‑effect profile than injectables. 1
When transdermal therapy is unsuitable, begin testosterone enanthate or cypionate at 50–100 mg weekly (intramuscular or subcutaneous) to provide more consistent serum concentrations than the traditional 100–200 mg every‑2‑weeks regimen. 1
Testosterone undecanoate can be used with a loading dose of 750 mg, a second 750 mg dose at 4 weeks, then 750 mg every 10 weeks (gluteal intramuscular injection). 1

Transdermal preparations minimize the peaks and troughs seen with injectable formulations, reducing hormonal fluctuations. 2
Injectable testosterone is associated with a markedly higher incidence of erythrocytosis (≈ 44 % vs ≈ 15 % with patches) and may carry greater cardiovascular risk due to supraphysiologic peaks and sub‑therapeutic troughs. [1][3]

Obtain serum testosterone measurements 2–3 months after therapy initiation to assess adequacy of dosing. [2][1]4
Repeat testosterone testing 2–3 months after any dose adjustment to confirm target attainment. [2][1]
Aim for mid‑normal adult testosterone levels of 450–600 ng/dL. [1][4]

For injectable formulations, draw testosterone midway between injections to capture a representative level. [2][1]
For transdermal gel, samples may be taken at any time; peak concentrations occur 6–8 hours post‑application. 2

If serum testosterone exceeds 750 ng/dL, reduce transdermal dose by ~20 mg daily (≈ 20.25 mg) or lower injectable dose by 25–50 %. 1
If testosterone is below 350 ng/dL, increase transdermal dose by ~20 mg daily or incrementally raise the injectable dose. 1

Once therapeutic levels are stable, schedule follow‑up assessments every 6–12 months. [2][1]4

Confirm low morning testosterone on at least two separate days. 2
Perform a digital rectal examination. [3][5]
Measure prostate‑specific antigen (PSA). [3][5]
Obtain baseline hematocrit or hemoglobin. [3][5]
Evaluate urinary symptoms with a standardized questionnaire. 3
Document sleep‑apnea history. 3
Recommend prostate biopsy if PSA > 4 ng/mL or if the digital rectal exam is abnormal. [3][5]

1–2 months: assess clinical efficacy and symptom improvement. 3
2–3 months and after any dose change: repeat testosterone, hematocrit/hemoglobin, and PSA measurements. [2][1]4
Every 3–6 months during the first year, then annually: monitor testosterone, hematocrit/hemoglobin, PSA, perform digital rectal examination, and reassess urinary and sleep‑apnea symptoms. [3][5]

Men attempting conception should avoid testosterone therapy because of spermatogenesis suppression. 4
Do not initiate therapy within 3–6 months after a major cardiovascular event (myocardial infarction or stroke). 4
Counsel overweight or obese patients on concurrent weight‑loss programs to mitigate cardiovascular risk. 4
Injectable testosterone may pose a higher cardiovascular risk than transdermal preparations. [2][4]

Check hematocrit at every visit during the first year of therapy. 3
Reported erythrocytosis rates: injectable testosterone ≈ 44 %; transdermal patches ≈ 15 %; low‑dose transdermal gel ≈ 3 %. 1
If hematocrit becomes elevated, reduce the testosterone dose or temporarily withhold therapy. 1

Alkylated oral testosterone should be avoided because of hepatotoxicity risk. 4
Discontinue therapy if there is no symptomatic improvement after 3–6 months despite achieving target testosterone levels. 4
Do not measure testosterone during rebound periods after stopping therapy, as values will not reflect true baseline. 4
Different gel concentrations are not interchangeable; a 1.62 % gel delivers more testosterone per gram than a 1 % gel and requires distinct dosing. 1