Re: Doc: Friend trying to get iron levels up

I assume that your friend wants to get her "iron levels up" because she is anemic?
Ferritin is not the best test to diagnose anemia - low ferritin IS the most sensitive test for iron-deficient anemia. However, there are many other causes of anemia where the ferritin will be normal, or even high. Also, because of its sensitivity, ferritin may be low in the absence of anemia. Normal or high ferritin does not necessarily rule out iron-deficient anemia because ferritin is an acute phase reactant (inflammation or psychological stress can trigger the "acute phase reaction" - the liver "gears up" for infection or injury by making acute phase proteins and activating a non-specific innate immune response).
Anemia is typically diagnosed by looking at the RBC (number of red blood cells in the peripheral blood), hemoglobin (the iron-carrying proteins in your red blood cells that carry oxygen), and/or hematocrit (how much of your blood is composed of RBCs). These numbers can tell you whether a person is anemic, but cannot tell you the cause of the anemia. It is when doctors are working up the anemia, trying to find a cause, that they will order a ferritin test (along with many others!)
I am concerned because your friend has kidney disease. Patients with serious, chronic kidney disease are often anemic (with a certain degree of kidney damage, anyone will become anemic!), but this has nothing to do with iron. This is because red blood cells are made in the bone marrow, and the bone marrow knows to make red blood cells because the kidney releases a hormone called erythropoeitin (EPO). If the kidneys are very damaged, they do not make enough EPO, and the bone marrow does not make enough RBCs as a result. Increasing iron levels will not do a thing in this instance, although sometimes there is a co-occuring iron deficiency (can be diagnosed with ferritin, transferrin saturation, or other tests) - if there is anemia due to kidney disease and iron deficiency, you have to increase EPO levels in addition to iron levels. The best treatment (besides a new kidney!) is synthetic EPO.