What could a low red blood cell count indicate?

Many causes. Chronic blood loss in menstrual blood, abnormal bleeding in intestine, nutritional, deficiencies, especially iron; lead poisoning, thalassemia, leukemia, hemolytic anemia etc. If you have low red blood count it should be investigated by a doctor.
Anemia. It can be an indication of anemia, though the hematocrit and hemoglobin levels are more important tests there are many causes of anemia.