If a recent lab test showed that your blood is “too thick,” you might have erythrocytosis. That tongue-twister simply means your body is packing extra red blood cells into every drop of blood. When blood gets crowded, it flows like syrup instead of water, raising your risk for clots, strokes, and heart attacks. Erythrocytosis can pop up for many reasons, high-altitude living, lung disease, dehydration, or even performance-boosting treatments like testosterone replacement therapy (TRT). The good news? Once you know the cause, you and your doctor can tackle it before trouble starts.
Key Takeaways
- Erythrocytosis means extra red blood cells; thicker, syrup-like blood raises clot, stroke, and heart attack risk, including during testosterone therapy.
- Doctors separate primary marrow disease from secondary causes like sleep apnea, COPD, high altitude, kidney tumors, smoking, or testosterone use.
- Early on, many feel nothing; rising hematocrit or hemoglobin plus headaches, dizziness, flushing, or tingling signal thickening blood requiring evaluation.
- On TRT, monitor hematocrit at baseline, 3, 6, and 12 months, then yearly; act near 52%, and stop treatment above 54%.
- Treat the root cause; consider dose changes, gels, therapeutic phlebotomy, low-dose aspirin, hydration, exercise, and avoiding unnecessary iron supplements for safety.
Table of Contents
Causes And Symptoms Of Erythrocytosis
What It Is
Erythrocytosis is a fancy way of saying your hematocrit, the percent of blood made of red cells, is higher than normal (above ~52 % in men or 48 % in women). Think of it as overcrowding in the bloodstream.
Primary vs. Secondary
Primary erythrocytosis happens when the bone marrow goes into overdrive all by itself. Polycythemia vera is the best-known example. Secondary erythrocytosis starts outside the marrow: low oxygen from sleep apnea, COPD, smoking, high mountains, kidney tumors that pump out extra erythropoietin, or medications such as testosterone.
Why It Happens
Your body makes red cells to carry oxygen. When oxygen feels scarce, say you live in Denver or struggle with lung issues, your kidneys release a hormone called erythropoietin (EPO). EPO tells bone marrow to build more red cells so every tissue still gets enough oxygen. Testosterone can mimic that signal by boosting EPO and lowering hepcidin, an iron regulator, so even normal-oxygen folks end up with surplus red cells.
Common Clues
Most people feel nothing at first. As counts climb, blood thickens and may cause:
- Headaches, dizziness, or blurred vision
- Ruddy (red-flushed) face or itchy skin after a hot shower
- Shortness of breath or chest pain with exertion
- Numb fingers or toes and, rarely, sudden clot-related events like a stroke or deep-vein thrombosis
Health Risks
Thicker blood flows sluggishly, stressing tiny vessels in the brain, kidneys, eyes, and heart. Studies link unchecked erythrocytosis to higher rates of heart attack and kidney filtration problems.
Diagnosing And Managing Erythrocytosis, Especially On Testosterone Replacement Therapy
How Doctors Confirm It
A simple complete blood count (CBC) shows hemoglobin and hematocrit. If hematocrit tops 52 % (men) or 48 % (women), a repeat test plus history and physical exam follow. Doctors search for smoking, lung disease, sleep apnea, high-altitude exposure, kidney problems, or hormone use. Oxygen saturation, erythropoietin levels, and JAK2 mutation testing help separate primary from secondary forms.
Special Case: TRT-Induced Erythrocytosis
Up to two-thirds of cisgender and transgender men on TRT will see their hematocrit rise, especially with high-dose injections. Guidelines tell prescribers to:
- Check baseline hematocrit before therapy.
- Re-check at 3, 6, and 12 months, then yearly.
- Reduce the dose, switch to transdermal gels, donate blood, or pause therapy if hematocrit hits 52 % and must stop when it exceeds 54 %.
Treatment Tools
Address the cause. Quitting smoking, treating sleep apnea, or adjusting testosterone often solves the problem. When levels stay high, doctors may order:
- Therapeutic phlebotomy – a quick blood draw (like donating) every few weeks to thin the blood.
- Lower-dose aspirin – to reduce clotting risk if no contraindication exists.
- Medication tweaks – such as switching TRT formulations or spacing injections.
Lifestyle Helpers
Staying well-hydrated, keeping blood pressure and cholesterol in check, and exercising moderately keep circulation smooth. Avoid iron supplements unless prescribed, extra iron can feed more red-cell production.
Prognosis
When treated promptly, most people lead normal lives without serious clots. Leaving hematocrit uncontrolled, however, raises the odds of heart attacks, strokes, and kidney trouble. Early action is key.
Understand Erythrocytosis
Frequently Asked Questions
It means you have more red blood cells than usual, making blood thicker than normal.
Polycythemia vera is a bone-marrow disease (primary), while erythrocytosis often starts from outside triggers like low oxygen or hormones.
Yes. High doses boost EPO and drop hepcidin, pushing red-cell counts up in as many as 60 % of users.
Most experts act at 52 % and insist on stopping therapy if the value reaches 54 %.
They can, but the normal hematocrit cut-offs are lower, so doctors adjust the numbers for age and sex.
Extra water helps if dehydration caused the rise, but true erythrocytosis needs medical evaluation and sometimes phlebotomy.
Therapeutic phlebotomy safely thins blood and is a first-line fix when counts stay high.
Check at baseline, 3 months, 6 months, 12 months, then yearly, or sooner if symptoms appear.
Most cases resolve by treating the cause, but rare genetic forms may need drugs like interferon under specialist care.
Yes. Thicker blood can slow kidney filtration and raise creatinine over time if left untreated.
