A high hematocrit level becomes dangerous when it significantly increases blood viscosity, leading to thicker blood that is more prone to clotting. Elevated hematocrit levels above normal ranges—generally above about 48.6% for men and 44.9% for women—can increase the risk of serious conditions such as blood clots, stroke, and heart attack. Very high hematocrit levels make the heart work harder to pump blood and reduce blood flow efficiency, which can cause symptoms like headaches, dizziness, fatigue, shortness of breath, blurred vision, and skin flushing. Levels above 54% in adult males are often considered high enough to cause concern and warrant medical evaluation and treatment to prevent complications.
Dangerous Effects of High Hematocrit
- Thickened blood can increase blood clot formation, potentially blocking vessels (thrombosis) leading to stroke or heart attack.
- Increased blood viscosity reduces blood flow, making oxygen delivery less efficient.
- The heart must pump more forcefully, increasing cardiovascular strain.
- Symptoms include severe headaches, dizziness, fatigue, shortness of breath, and visual disturbances.
- Skin changes such as flushing and itching may occur.
Thresholds and Conditions
- Normal upper limits are about 48.6% for men and 44.9% for women.
- Levels above 54% in men are generally considered high and dangerous.
- Underlying diseases like polycythemia vera and chronic lung disease can cause dangerous elevation.
- Dehydration or high-altitude living may cause transient rises.
When to Seek Medical Attention
- Persistent or severe symptoms as above.
- Hematocrit levels significantly above normal range.
- Any signs of blood clots or cardiovascular complications.
High hematocrit is a medical concern because of its association with increased risk of blood clots, stroke, and heart attack, and it requires proper diagnosis and management by healthcare professionals.