what is the difference between iron deficiency, anemia and Hb deficiency? How do you test for them?


Context: I’m trying to understand how someone can have nomal Hb and low ferritin

In: 3

Iron is an important building block to make hemoglobin, the oxygen carrying molecule of red blood cells. Without iron your body will have problems creating red blood cells

Iron deficiency can come from various reasons, the most important low dietary intake, problems absorbing iron from the intestine (diseases like celiac disease) or excessive losses (bleeding due to cuts, surgery or menstruation)

Anemia is a low amount of hemoglobin in your blood. It may be production problems like low iron availability, genetic diseases that inhibits hemoglobin production (thalassemia, sickle cell disease) or blood loss.

Anemia is a deficiency in hemoglobin (Hb) or hematocrit (Hct). It is a specific lab value definition, not diagnosed just based on symptoms. It leads to decreased oxygen carrying capacity and therefore fatigue. There are many, many causes of anemia that fall into two categories: excessive destruction of old RBCs or insufficient production of new RBCs.

Iron deficiency is a one cause of anemia that leads to insufficient production of RBCs. Iron is a critical component of Hb so without it, the bone marrow factory can’t keep up with the demand. Folate deficiency or a set of diseases called thalassemias also can cause a production-deficient anemia. In the case of low ferritin and normal Hb, that probably means the patient is simply running out of iron stores and is likely about to develop an iron deficiency anemia.

Again, there are many other causes. For example, sickle cell disease/trait leads to RBCs getting deformed and then destroyed earlier than the normal ~120 day life span. This sometimes occurs in episodes and often requires a blood transfusion if severe enough.