How should I manage a hemoglobin of 18.3 g/dL in a patient receiving testosterone therapy?

Management of Hemoglobin 18.3 g/dL on Testosterone Therapy

You must temporarily discontinue testosterone therapy immediately until the hemoglobin falls below 17.5 g/dL (hematocrit <50%), then resume at a reduced dose of 25–50% lower than the current regimen. 1

Immediate Actions Required

Stop testosterone now. A hemoglobin of 18.3 g/dL indicates clinically significant erythrocytosis that requires intervention. 2, 1 The FDA label explicitly states that hemoglobin and hematocrit levels should be checked periodically to detect polycythemia, and therapy adjustments are necessary when elevations occur. 3

Phlebotomy Consideration

• Therapeutic phlebotomy is indicated if hematocrit exceeds 54% or if the patient has cardiovascular risk factors (hypertension, diabetes, coronary disease, cerebrovascular disease, peripheral vascular disease). 1
• Even without reaching 54%, hematocrit >52% increases blood viscosity and can aggravate vascular disease. 1
• Calculate the hematocrit from hemoglobin: with Hgb 18.3 g/dL, the estimated hematocrit is approximately 54.9%, which meets the threshold for phlebotomy. 1

Resuming Testosterone Therapy

Do not restart testosterone until hemoglobin normalizes to <17.5 g/dL (hematocrit <50%). 1 When resuming:

• Reduce the dose by 25–50% from the previous regimen. 1
• Switch from injectable to transdermal formulations if the patient was on injections—this dramatically reduces erythrocytosis rates from 43.8% with injectables to 2.8–15.4% with transdermal preparations. 1, 4
• Target mid-normal testosterone levels (400–600 ng/dL) rather than high-normal or supraphysiologic levels. 1

Why Injectable Formulations Are Higher Risk

Injectable testosterone (enanthate, cypionate, undecanoate) produces higher peak testosterone levels and greater erythropoietic stimulation compared to transdermal gels or patches. 1, 4 The Endocrine Society guideline notes that erythrocytosis is the most frequent adverse event in testosterone trials, with higher frequency in older men. 2

Monitoring Protocol

Check hemoglobin/hematocrit every 3 months for the first year after restarting, then every 6 months thereafter. 1 This is more frequent than some guidelines suggest, but erythrocytosis develops in 15–44% of men on testosterone therapy, making close surveillance essential. 1

Additional monitoring at each visit:

• Total and free testosterone levels 1
• Blood pressure 1
• Lipid panel 1
• PSA and digital rectal exam 1
• Screen for sleep apnea symptoms 1

Critical Pitfalls to Avoid

Do not ignore elevated hemoglobin/hematocrit. Erythrocytosis is the most common serious complication requiring intervention in testosterone therapy. 2, 1 The Endocrine Society guideline explicitly states that clinicians should withhold therapy until hematocrit returns to normal range. 2

Do not assume blood donation alone will control erythrocytosis. A 2017 study found that 44% of men on testosterone had persistently elevated hemoglobin ≥180 g/dL despite repeat blood donations, and donation was insufficient to maintain hematocrit below 54%. 5 Dose reduction or formulation change is necessary.

Do not supplement iron if the patient is iron deficient until hematocrit is controlled. Iron repletion will further increase hematocrit in the setting of testosterone-induced erythropoiesis. 1

Do not use testosterone cypionate interchangeably with other formulations due to differences in duration of action and erythrocytosis risk. 3

Cardiovascular Risk Context

While the exact hematocrit threshold for increased neuro-occlusive or cardiovascular events remains uncertain, the frequency of such events in clinical trials has been very low. 2 The recent TRAVERSE trial and meta-analyses indicate testosterone therapy does not significantly increase major adverse cardiovascular events when appropriately monitored. 6 However, elevated hematocrit >52% increases blood viscosity and theoretical thrombotic risk, particularly in patients with pre-existing vascular disease. 1, 7

The current hematocrit cutoff of 54% used in guidelines may be somewhat arbitrary and lacks strong scientific basis, but it represents a consensus threshold for intervention. 2, 7 In real-world practice, intervening at lower thresholds (50–52%) in high-risk patients is prudent. 1