Red Blood Cell (RBC) Count
A red blood cell count measures the number of erythrocytes in your blood, often serving as an early indicator of illness before symptoms appear.
Overview
A red blood cell (RBC) count measures the number of red blood cells, also known as erythrocytes, in your blood. These cells are produced in your bone marrow and contain hemoglobin, an iron-rich protein essential for transporting oxygen from your lungs to every cell in your body. Because cells require oxygen to function, energy production, and growth, an abnormal RBC count is often an early sign of health issues.
What is it used for?
This test is typically part of a complete blood count (CBC), which evaluates the number and type of cells in your blood. It is primarily used to help diagnose red blood cell disorders, such as anemia, where the body fails to produce enough healthy red blood cells.
Why do I need a red blood cell count?
You may receive this test during a routine checkup, while monitoring chronic conditions like chronic kidney disease, or if you are undergoing treatments that affect blood cell counts, such as chemotherapy. You may also need the test if you exhibit symptoms of an abnormal count.
Symptoms of a low RBC count
- Shortness of breath
- Weakness or fatigue
- Headache
- Dizziness
- Arrhythmia (irregular heartbeat)
- Pale skin
Symptoms of a high RBC count
- Headache
- Dizziness
- Vision problems
What happens during the test?
A health care professional will collect a small blood sample from a vein in your arm using a needle. The process typically takes less than five minutes. There are no special preparations required, and risks are minimal, limited to slight pain or bruising at the puncture site.
What do the results mean?
Results indicate whether your count is normal, low, or high. Your provider will interpret these findings alongside your medical history and other test results.
Conditions associated with a low RBC count:
- Anemia
- Leukemia (blood cancer)
- Malnutrition
- Multiple myeloma (bone marrow cancer)
- Kidney failure
- Blood loss
- Alcohol use disorder (AUD)
- Pregnancy
Conditions associated with a high RBC count:
- Dehydration
- Heart disease
- Polycythemia vera (bone marrow disorder)
- Scarring of the lungs (often due to smoking)
- Lung disease
- Kidney cancer
- Sleep apnea
- High altitude or misuse of performance-enhancing drugs like anabolic steroids
Additional Testing
If your results are abnormal, your provider may order further tests, including a reticulocyte count (to check for immature red blood cells), iron tests, or a vitamin B test.