An elevated RBC level is diagnosed with a test called the RBC count, explains MedlinePlus. The test determines how many red blood cells are present in a sample of blood.
The RBC count is usually done along with the other components of the complete blood count, states MedlinePlus. The test helps diagnose anemia and other conditions that affect RBC levels. A normal RBC count ranges from 4.2 to 5.4 million cells per microliter in women and 4.7 to 6.1 million cells per microliter in men.
Because RBCs are responsible for supplying the tissues with oxygen, RBC count increases temporarily when a person moves to an area with a high altitude, notes MedlinePlus. There are also several medical conditions that result in an elevated RBC count. Congenital heart disease, scarring of the lungs, dehydration, kidney tumors and right-side heart failure are all potential causes of an increased RBC count. Smoking cigarettes and taking medications such as gentamicin or methyldopa can also increase RBC levels.
Polycythemia vera is a condition characterized by the production of too many red blood cells in the bone morrow, explains the National Cancer Institute. The extra cells build up in the spleen, causing the spleen to become enlarged. Elevated blood cell counts can also cause blood clots to form.