Red blood cell lab tests can be performed to determine general health status. They can also help with diagnosis or monitoring of diseases that affect blood cells such as anemia, inflammation, bleeding disorders, cancer, or infection. Some common examples include:

• The red blood cell count or erythrocyte count determines the total number of RBCs per microliter of blood. A normal value is 4.2-5.4 million/μL. This test can be helpful in diagnosing anemia (low RBC levels) or polycythemia (high RBC levels).
• The percentage of reticulocyte test reflects the function and activity of the bone marrow because it determines the number and/or percentage of reticulocytes (new RBCs) in the blood. A normal percentage of reticulocytes is 0.4-3.0%. Values higher than this suggest that the bone marrow is undergoing erythropoiesis at a higher than normal rate. This might be expected if the patient was experiencing some type of chronic deprivation of oxygen which would cause an increase of EPO release from the kidney. A low reticulocyte count indicates a condition that negatively affects RBC production such as a bone marrow disorder or a nutritional deficiency of iron, vitamin B-12, or folate.
• The hemoglobin level test measures the level of hemoglobin in the blood. A normal hemoglobin level for females is 12.5-15.5 g/dL and 13.5-17.5 g/dL for males. This test usually mirrors the RBC count results.
• The hematocrit test indicates the portion of the blood that consists of packed red blood cells. The hematocrit test is expressed as a percentage by volume. A low percentage can be suggestive of some condition that would decrease RBC production or a condition that breaks RBCs down too quickly. A high hematocrit suggests excessive hematopoiesis or a decrease in plasma volume due to dehydration.
• Mean corpuscular volume (MCV) is a blood test that measures the average size of a person’s red blood cells. Microcytic (small) RBCs can indicate iron deficiency while macrocytic (large) RBCs can indicate anemia due to vitamin B-12 or folate deficiency, liver disease, or hypothyroidism.
• Mean corpuscular hemoglobin concentration (MCHC) is a blood test that determines the average concentration of hemoglobin in red blood cells. Hemoglobin is what makes red blood cells red in color. A low MCHC is associated with hypochromic RBCs, which are red blood cells that appear paler than what is expected.