Anemia is a blood disorder where the body doesn’t have enough healthy red blood cells or hemoglobin, resulting in poorly oxygenated tissues throughout the body. This condition takes many forms, ranging from mild to severe depending on the cause.
Anemia in males is a hemoglobin below 13.5 g/dL or a hematocrit less than 41%, and in females it’s a hemoglobin below 12.0 g/dL or a hematocrit less than 36%, but those numbers can differ based on which guidelines you’re using. Also, people with chronic respiratory diseases like emphysema or medical problems like malnutrition may have symptoms of anemia even at normal levels of hemoglobin and hematocrit. In addition, those living at altitude can have high levels of hemoglobin and hematocrit to help deal with the lower oxygen levels. So it’s good to keep in mind that these guidelines aren’t appropriate for everyone. Now, the most common signs and symptoms of anemia are dyspnea with exertion and at rest, fatigue, pallor, and a hyperdynamic state like bounding pulses and palpitations.
If someone is anemic, the first thing to look at is the mean corpuscular volume or MCV. An MCV of less than 80 femtoliters is low, so microcytic, between 80 and 100 femtoliters is normal, so normocytic, and above 100 femtoliters is high, so macrocytic. Of course, some individuals might have a few types or causes of anemia mixed together, and that’s where things get more complicated. Most microcytic and macrocytic anemias are caused by a problem in producing either red blood cells or hemoglobin, and in those situations we can measure the reticulocyte production index (RPI) or corrected reticulocyte count (CRC). This number is the percentage of red blood cells that are reticulocytes, or immature, and is normally between 0.5 and 2.5%. A person with anemia and less than 2% RPI means that their body is not capable of producing enough red blood cells. In certain normocytic anemias that are caused by the loss or destruction of red blood cells, the RPI is above 2% because the body increases red blood cell production to replace the ones that were lost.