Haematocrit is the percentage of red blood cells in your blood. Haemoglobin is the protein inside those cells that helps carry oxygen.
Testosterone can stimulate red blood cell production, which may raise these markers. Although elevated HCT and HB are rare, it is a well-known and manageable response to TRT.
Why It Happens
Testosterone boosts red blood cell production (erythropoiesis). This is helpful in many cases but, if haematocrit or haemoglobin gets too high, it can make the blood more viscous and place added strain on the cardiovascular system.
Monitoring
We test your levels:
At 8 weeks after starting TRT
Every 4 months ongoing
This helps us catch any changes early and adjust your plan accordingly.
Target Ranges
Haematocrit: Aim for < 0.52
Haemoglobin: Aim for < 180 g/L
Values higher than this increase the risk of side effects and require review.
What You Might Feel
Most people feel fine even with elevated results. In rare cases, symptoms can include:
Headaches
Facial redness
Dizziness
Fatigue
High blood pressure
Let us know if you experience any of these.
What We Do About It
If your levels are elevated:
We’ll ask you to visit your GP for a sleep study — sleep apnea is a common underlying cause.
We’ll remind you to stay hydrated before your blood test, as dehydration can falsely raise readings.
Your doctor may adjust your TRT dose or injection frequency.
We no longer routinely refer patients for blood donations unless clinically advised by your GP.
Other Contributors
Other things that can raise haematocrit or haemoglobin:
Smoking
Living at high altitude
Untreated sleep apnea
Not drinking enough water before blood tests
Elevated haematocrit or haemoglobin is a manageable side effect of TRT. We’ll guide you through next steps if it happens.
Ensure proper hydration before blood work and consult your GP if a sleep study is recommended. Regular testing helps us keep treatment safe and effective.