How does the doctor know if the diagnosis is anemia?

CBC: Anemia is condition where the hemoglobin level is less than the normal range level- diagnosed by getting a simple blood test- i.e. Complete blood count. To diagnose anemia is not difficult. However to find the cause of anemia sometimes is complex/difficult and requires involvement of a specialist -i.e. Hematologist.

Low red blood count: If you have symptoms and signs suggestive of anemia like tiredness, pale mucus membranes or obvious bleeding, your doctor will run a blood test indicating the percent of red blood cells in your blood, the parameters of the cells to determine if you do not make enough or are nutritionally deficient, etc. This is a usually obvious diagnosis but the cause takes a little work to find out.