Low hemoglobin levels usually indicate that a person has anemia. If a disease or condition affects the body’s production of red blood cells, the hemoglobin levels may drop. Fewer red blood cells and lower hemoglobin levels may cause the person to develop anemia. Porphyria. There are several kinds of anemia: Iron-deficiency anemia is the most common type. Low hemoglobin levels can be caused by a variety of conditions, such as lack of iron or blood loss, and could lead to anemia causing symptoms of fatigue and dizziness. What is … Vasculitis. Thalassemia. A low hemoglobin count is generally defined as less than 13.5 grams of hemoglobin per deciliter (135 grams per liter) of blood for men and less than 12 grams per deciliter (120 grams per liter) for … Sickle cell anemia. When the body destroys RBC faster than it produces them, low hemoglobin count occurs, such as in these conditions: Enlarged spleen. A low hemoglobin count can be associated with a disease or condition that causes your body to have too few red blood cells. This can occur if: Your body produces fewer red blood cells than usual