A complete blood count, or CBC, is an easy and very common test that screens for certain disorders that can affect your health. A CBC determines if there are any increases or decreases in your blood cell counts. Normal values vary depending on your age and your gender. Your lab report will tell you the normal value range for your age and gender. A complete blood count test measures several components and features of your blood, including:Red blood cells, which carry oxygen White blood cells, which fight infection Hemoglobin, the oxygen-carrying protein in red blood cells Hematocrit, the proportion of red blood cells to the fluid component, or plasma, in your blood Platelets, which help with blood clotting Abnormal increases or decreases in cell counts as revealed in a complete blood count may indicate that you have an underlying medical condition that calls for further evaluation.