Total RBC count is a blood test that directly counts all the RBCs in a small sample of blood, this test is also termed as erythrocytes count. It is an important test because RBCs contain haemoglobin which carries oxygen to the body tissues which require oxygen to function. A hematocrit test measures the ratio of RBCs in an individuals blood. A RBC test will be recommended by doctors if they suspect the patient with conditions that affect RBCs, or if you show symptoms of low blood oxygen which may include confusion, irritability, irregular breathing etc.