From the Guidelines
A Hematocrit (HCT) test is crucial for patients undergoing Testosterone Replacement Therapy (TRT) to monitor for erythrocytosis, a condition where the body produces too many red blood cells, as it can lead to serious cardiovascular events. The primary reason for conducting an HCT test in these patients is to assess the risk of polycythemia, which can increase the viscosity of blood and subsequently raise the risk of heart attack, stroke, and deep vein thrombosis 1.
Importance of HCT Monitoring
According to a study published in the New England Journal of Medicine, there is a direct relation between testosterone dosage and the incidence of erythrocytosis, with higher doses leading to a greater risk of this condition 1. For instance, erythrocytosis occurred in 2.8 percent of men receiving 5 mg per day by nonscrotal patches and in 11.3 percent and 17.9 percent of men treated with gel preparations of 50 mg per day and 100 mg per day, respectively.
Recommendations for HCT Testing
Given the potential risks associated with erythrocytosis, it is recommended that HCT levels be monitored in men receiving TRT. The monitoring should include:
- Measuring HCT before starting therapy to establish a baseline
- Regular monitoring at 3-6 month intervals during the first year of therapy
- Annual monitoring thereafter
- Consideration of therapeutic phlebotomy if HCT exceeds 54%
Lifestyle Modifications
In addition to medical interventions, patients with elevated HCT levels should consider lifestyle modifications to help manage their condition, including:
- Increasing hydration to prevent dehydration, which can artificially elevate HCT results
- Avoiding smoking
- Limiting alcohol consumption
These measures can help mitigate the risks associated with erythrocytosis and ensure the safe use of TRT. As noted in another study, injections appear to be associated with a greater risk of erythrocytosis than topical preparations, highlighting the need for careful monitoring and management of HCT levels in patients undergoing TRT 1.
From the FDA Drug Label
- 3 Polycythemia
Increases in hematocrit, reflective of increases in red blood cell mass, may require lowering or discontinuation of testosterone. Check hematocrit prior to initiating treatment. It would also be appropriate to re-evaluate the hematocrit 3 to 6 months after starting treatment, and then annually If hematocrit becomes elevated, stop therapy until hematocrit decreases to an acceptable concentration. An increase in red blood cell mass may increase the risk of thromboembolic events.
A Hematocrit (HCT) test is needed to monitor for polycythemia, which is an increase in red blood cell mass that may occur with testosterone replacement therapy (TRT). This is important because an increase in red blood cell mass can increase the risk of thromboembolic events. The HCT test should be checked:
- Prior to initiating treatment
- 3 to 6 months after starting treatment
- Annually thereafter If the hematocrit becomes elevated, testosterone therapy should be stopped until the hematocrit decreases to an acceptable concentration 2.
From the Research
Importance of Hematocrit (HCT) Test
- A Hematocrit (HCT) test is needed to monitor patients undergoing Testosterone Replacement Therapy (TRT) due to the risk of secondary erythrocytosis, a condition characterized by an increase in red blood cell production 3, 4, 5.
- Secondary erythrocytosis is one of the most common adverse events associated with testosterone therapy, and it may predispose patients to adverse vascular events 3, 4.
Risks Associated with Elevated Hematocrit Levels
- Elevated hematocrit levels (above 54%) have been linked to an increased risk of venothromboembolism (VTE) and other cardiovascular events 5, 6.
- Men undergoing TRT have a 315% greater risk of developing erythrocytosis (defined as Hct > 0.52) compared to control groups 5.
Monitoring and Management of Erythrocytosis
- Regular laboratory monitoring, including HCT tests, is recommended for patients on TRT to detect early signs of erythrocytosis 4, 6.
- If the hematocrit exceeds 54%, therapy should be decreased or discontinued until the hematocrit normalizes 6.
- Combination therapy with sodium-glucose cotransporter-2 inhibitors (SGLT-2i) and TRT may pose a higher risk of erythrocytosis, and periodic hematocrit assessment is recommended for these patients 7.