A red blood cell count is a blood test that shows the level of red blood cells.  It is normally ordered as part of a complete blood count.  Red blood cells contain hemoglobin, a red protein that carries oxygen to the tissues and helps remove carbon dioxide.  Insufficient red blood cells prevent the tissues from receiving enough oxygen or removing carbon dioxide. 
Red blood cells are produced in the bone marrow, the soft fatty substance in the bones.  They live for approximately 100 days and constantly being replaced.
 The red blood cell count is important if the patient is complaining of (presenting) some of the following conditions:
Weakness
Fatigue

Being tired all the time

Being unusually pale

Headaches

Recent vision problems

Dizziness

NORMAL RESULTS

The red blood cell count is measured in cells per microliter (one millionth of a liter).  The normal range is different for men and women.  The normal results are:
Males: 4.7 to 6.1 million cells per microliter (cells/mcL)
Females: 4.2 to 5.4 million cells/mcL

HIGHER THAN NORMAL RESULTS

Higher than normal red blood cells may be caused by:
Smoking

Heart disease

Enlargement of the heart
Dehydration
Kidney problems

Lung problems

Bone marrow disease

LOWER THAN NORMAL RESULTS

A lower than normal number of red blood cells may be caused by:
Anemia

Bone marrow problems

Rupture of red blood cells

Hemorrhage (bleeding)

Leukemia
Vitamin or nutrient deficiency

Overhydration

Pregnancy