The Iron Story: How Iron Prevents Anemia in Patients With Kidney Disease
What Is Anemia?
When your doctor tells you that your blood count is low, it means you do not have enough red blood cells (RBCs) in your blood. If your count is low enough for you to feel sick, it is called anemia.
Anemia will cause you to feel very tired, eat poorly, and even feel short of breath. Anemia, over a long period of time, can cause you to have heart problems. If you already have heart problems, it can make those problems worse.
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 The Kidneys, Iron, and Anemia
The kidneys control your health in many ways. One way is by helping your body to have enough RBCs. Your body is always making new RBCs as old ones die.
The healthy kidney produces a hormone called erythropoietin (EPO). (A hormone is a body fluid that acts as a messenger delivering needed material from one part of the body to another.) RBCs are formed in the bone marrow with the help of this hormone. The bone marrow is also supplied with a very small amount of iron, which helps to build healthy new RBCs. Then the RBCs carry oxygen to all parts of the body. Every living human cell needs oxygen to live. |
What Happens When the Kidneys Don't Work Properly?
Usually patients with chronic kidney disease have a type of anemia that is caused by two problems. The first is that there are too few red RBCs. This is because the kidney is no longer making the hormone erythropoietin.
The second is that there may be too little iron. Too little iron may be caused by a number of problems. Your special kidney disease diet may not allow you to eat enough iron-rich foods. Your body may not be able to absorb enough iron. Like many patients with kidney disease, you may lose blood, and when you lose blood you lose iron. Finally, as you will see, if you receive EPO (Epogen®, epoetin alfa, a product of Amgen, Inc), your body may use all its stored-up iron to make new RBCs.
What Can Be Done to Prevent or Control Anemia?
Taking EPO. As a patient with chronic kidney disease, you may not be making enough erythropoietin; therefore, you may receive a man-made form of erythropoietin. EPO may be given by injection into your vein (or during your hemodialysis treatment). This is an intravenous or IV injection. It may also be given by a very small injection under your skin. This is a subcutaneous injection.
Taking iron. Taking iron by mouth (oral iron) may be enough if you are not receiving EPO. However, most patients with kidney disease and almost all patients on hemodialysis who are taking EPO will need to receive iron through the vein. Oral iron will not be enough once the EPO begins to make new RBCs. The amount of iron your body stores will not be enough to make all the new RBCs you need. Without enough iron, EPO cannot completely correct anemia.
If you are on EPO and you are not getting enough iron, your doctor will treat you with intravenous iron. You will receive intravenous iron during your hemodialysis treatment or when you come to your doctor's office or clinic.
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 How Your Doctor Knows When to Give You Iron
The blood tests that you take each month will give your doctor a picture of how healthy your RBCs are. They will show whether your RBCs are receiving enough iron. (These tests may be taken less often if your RBC count remains good.)
There are blood tests that show how your RBCs are doing. There are blood tests that show where the iron is in your body and how it is being used. |
Your RBC tests are:
- Hemoglobin: This is the part of the RBC containing the iron that carries oxygen. In most patients, it should read between 11 and 12 g/dL.
- Hematocrit: This is the measure that tells how many RBCs are in a specific amount of blood. In most patients, it should read between 33% and 36%. (This test is not as accurate as the hemoglobin test. It may change slightly depending on how long the blood sits in the tube before it is measured in the laboratory or how much fluid you have in your body.)
The two iron blood tests you should know about are:
- Ferritin: This is a protein that keeps iron in "storage" until it is needed. The ferritin should be more than
100 ng/mL and less than 800 ng/mL. Your doctor will know when to start iron and when to stop it.
When you have a serious infection, it is possible that your body will hold onto the iron in storage. In this case, you may have a high ferritin level even though you don't have enough iron in your blood cells. You should receive treatment for your infection before continuing to receive your supplemental iron therapy.
- Transferrin Saturation: Transferrin is a protein that takes the iron from the storage protein (ferritin), or the iron that you're being treated with, and brings it to the bone marrow where it may be used to build healthy RBCs. This blood test measures the amount of iron on the transferrin protein. If your transferrin saturation is less than 20%, it means you do not have enough iron for your RBCs. Transferrin saturation should be between 20% and 50%.
If you are receiving IV iron and are going to have your iron blood tests done, your doctor will tell you if you need to be off the IV iron before these tests are ordered.
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 What Type of Iron May Your Doctor Prescribe?
There are two ways of receiving iron if diet alone is not enough. Your doctor may first prescribe oral iron (pills that you can buy without a prescription). Oral iron is usually given three times a day between meals.
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- Take iron one hour before or two hours after a meal
- Do not take with antacids
- Do not take with phosphate binders
- Avoid alcohol
- If you begin to get constipated, have nausea, or a feeling of fullness, try increasing your iron dose slowly. Take stool softeners to help avoid constipation and let your doctor know if you begin to have this problem
If you are unable to reach a good RBC count with oral iron, your doctor may prescribe intravenous iron. This is the iron injected into your bloodstream.
 EPO and iron work together to help your body make healthy RBCs. Your doctor will decide how to give you these drugs.
The US Food and Drug Administration has approved three types of intravenous iron injectable products for use. These are iron sucrose injection, iron dextran injection, and sodium ferric gluconate complex in sucrose injection, also known as iron gluconate. All of these will help to increase the amount of iron you have in your body. There are some differences among them, however. Among these differences are how quickly they work, whether or not a test dose is required, the types of side effects you might have, their approved indications, and the size of your dose. Your doctor will decide which is best for you.
A person can experience an allergic reaction to intravenous iron just as they do to other medications. It is important for you to immediately notify your doctor or a member of the dialysis staff if you experience:
- Flushing
- Difficulty breathing
- Itching
- Rash
- Any unusual symptoms during or just after the drug was given
If you have had an allergic reaction to intravenous iron in the past, you need to discuss with your doctor whether a different type of intravenous iron may be better for you.
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