In general, the reference ranges are as follows: White blood cells have a cell density ranging from 4,500 to 11,000 cells per microliter (cells/mcL). Men: 4.5 million to 5.9 million cells per microliter; women: 4.1 million to 5.1 million cells per microliter. Hemoglobin levels range from 14 to 17.5 grams per deciliter (gm/dL) in males and 12.3 to 15.3 gm/dL in women. Platelets count between 150,000 and 400,000 per microliter. These figures are for an individual's "normal" white blood cell, red blood cell, and platelet counts. A healthy person should have neither too many nor too few of these cells. Changes in these numbers are often used as markers for disease or injury. For example, people who take steroids such as prednisone may see their white blood cell counts rise above what is considered normal. That can be an early sign of infection - something to watch for if someone takes steroids for more than a couple of weeks. A normal CBC test results in the absence of any abnormalities. Abnormalities include increases or decreases in any of the three main types of blood cells - white blood cells, red blood cells, or platelets - or changes over time in any of these numbers. For example, people who take drugs such as thiopurines, which are used to treat cancer, can develop lymphopenia - low numbers of lymphocytes- which can lead to infections without symptoms. People who have immune systems that work well but still might get sick occasionally could have subclinical infections that don't show up on tests.