Red blood cells (RBC, erythrocytes)

A red blood cell count is a blood test that your doctor uses to find out how many red blood cells (RBCs) you have. It's also known as an erythrocyte count. The test is important because RBCs contain hemoglobin, which carries oxygen to your body's tissues. The amount of oxygen that's delivered to your body's tissues depends on the number of red blood cells you have and how well they work.

Normal RBC ranges are:

Male: 4.7 to 6.1 million cells per microliter (cells/mcL) Female: 4.2 to 5.4 million cells/mcL. Pregnancy: slightly lower than normal adult values.

When you don't have enough healthy red blood cells, you have a condition called anemia. This means your blood has lower than normal hemoglobin (Hgb) levels. Anemia is a common side effect in patients with cancer.

A high red blood cell count may be a symptom of a disease or disorder, although it doesn't always indicate a health problem. Health or lifestyle factors can cause a high red blood cell count. Medical conditions that can cause an increase in red blood cells include: Heart failure, causing low blood oxygen levels.