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What is anemia?
Anemia is a condition in which the body has fewer red blood cells than normal. Red blood cells carry oxygen to tissues and organs throughout the body and enable them to use energy from food. With anemia, red blood cells carry less oxygen to tissues and organs—particularly the heart and brain—and those tissues and organs may not function as well as they should.
How is anemia related to chronic kidney disease?
Anemia commonly occurs in people with chronic kidney disease (CKD)—the permanent, partial loss of kidney function. Anemia might begin to develop in the early stages of CKD, when someone has 20 to 50 percent of normal kidney function. Anemia tends to worsen as CKD progresses. Most people who have total loss of kidney function, or kidney failure, have anemia.1 A person has kidney failure when he or she needs a kidney transplant or dialysis in order to live. The two forms of dialysis include hemodialysis and peritoneal dialysis. Hemodialysis uses a machine to circulate a person’s blood through a filter outside the body. Peritoneal dialysis uses the lining of the abdomen to filter blood inside the body.
What are the kidneys and what do they do?
The kidneys are two bean-shaped organs, each about the size of a fist. They are located just below the rib cage, one on each side of the spine. Every day, the kidneys filter about 120 to 150 quarts of blood to produce about 1 to 2 quarts of urine.
Healthy kidneys produce a hormone called erythropoietin (EPO). A hormone is a chemical produced by the body and released into the blood to help trigger or regulate particular body functions. EPO prompts the bone marrow to make red blood cells, which then carry oxygen throughout the body.
What causes anemia in chronic kidney disease?
When kidneys are diseased or damaged, they do not make enough EPO. As a result, the bone marrow makes fewer red blood cells, causing anemia. When blood has fewer red blood cells, it deprives the body of the oxygen it needs.
Other common causes of anemia in people with kidney disease include blood loss from hemodialysis and low levels of the following nutrients found in food:
- vitamin B12
- folic acid
These nutrients are necessary for red blood cells to make hemoglobin, the main oxygen-carrying protein in the red blood cells.
If treatments for kidney-related anemia do not help, the health care provider will look for other causes of anemia, including
- other problems with bone marrow
- inflammatory problems—such as arthritis, lupus, or inflammatory bowel disease—in which the body’s immune system attacks the body’s own cells and organs
- chronic infections such as diabetic ulcers
What are the signs and symptoms of anemia in someone with chronic kidney disease?
The signs and symptoms of anemia in someone with CKD may include
- fatigue, or feeling tired
- problems with concentration
- difficulty breathing or shortness of breath
- chest pain
Anyone having difficulty breathing or with shortness of breath should seek immediate medical care. Anyone who has chest pain should call 911.
What are the complications of anemia in someone with chronic kidney disease?
Heart problems are a complication of anemia and may include
- an irregular heartbeat or an unusually fast heartbeat, especially when exercising.
- the harmful enlargement of muscles in the heart.
- heart failure, which does not mean the heart suddenly stops working. Instead, heart failure is a long-lasting condition in which the heart can’t pump enough blood to meet the body’s needs.
How is anemia in chronic kidney disease diagnosed?
A health care provider diagnoses anemia based on
- a medical history
- a physical exam
- blood tests
Taking a medical history is one of the first things a health care provider may do to diagnose anemia. He or she will usually ask about the patient’s symptoms.
A physical exam may help diagnose anemia. During a physical exam, a health care provider usually examines a patient’s body, including checking for changes in skin color.
To diagnose anemia, a health care provider may order a complete blood count, which measures the type and number of blood cells in the body. A blood test involves drawing a patient’s blood at a health care provider’s office or a commercial facility. A health care provider will carefully monitor the amount of hemoglobin in the patient’s blood, one of the measurements in a complete blood count.
The Kidney Disease: Improving Global Outcomes Anemia Work Group recommends that health care providers diagnose anemia in males older than age 15 when their hemoglobin falls below 13 grams per deciliter (g/dL) and in females older than 15 when it falls below 12 g/dL.2 If someone has lost at least half of normal kidney function and has low hemoglobin, the cause of anemia may be decreased EPO production.
Two other blood tests help measure iron levels:
- The ferritin level helps assess the amount of iron stored in the body. A ferritin score below 200 nanograms (ng) per milliliter may mean a person has iron deficiency that requires treatment.2
- The transferrin saturation score indicates how much iron is available to make red blood cells. A transferrin saturation score below 30 percent can also mean low iron levels that require treatment.2
In addition to blood tests, the health care provider may order other tests, such as tests for blood loss in stool, to look for other causes of anemia.
How is anemia in chronic kidney disease treated?
Depending on the cause, a health care provider treats anemia with one or more of the following treatments:
The first step in treating anemia is raising low iron levels. Iron pills may help improve iron and hemoglobin levels. However, for patients on hemodialysis, many studies show pills do not work as well as iron given intravenously.2
If blood tests indicate kidney disease as the most likely cause of anemia, treatment can include injections of a genetically engineered form of EPO. A health care provider, often a nurse, injects the patient with EPO subcutaneously, or under the skin, as needed. Some patients learn how to inject the EPO themselves. Patients on hemodialysis may receive EPO intravenously during hemodialysis.
Studies have shown the use of EPO increases the chance of cardiovascular events, such as heart attack and stroke, in people with CKD. The health care provider will carefully review the medical history of the patient and determine if EPO is the best treatment for the patient’s anemia. Experts recommend using the lowest dose of EPO that will reduce the need for red blood cell transfusions. Additionally, health care providers should consider the use of EPO only when a patient’s hemoglobin level is below 10 g/dL. Health care providers should not use EPO to maintain a patient’s hemoglobin level above 11.5 g/dL.2 Patients who receive EPO should have regular blood tests to monitor their hemoglobin so the health care provider can adjust the EPO dose when the level is too high or too low.2 Health care providers should discuss the benefits and risks of EPO with their patients.
Many people with kidney disease need iron supplements and EPO to raise their red blood cell count to a level that will reduce the need for red blood cell transfusions. In some people, iron supplements and EPO will improve the symptoms of anemia.
Red Blood Cell Transfusions
If a patient’s hemoglobin falls too low, a health care provider may prescribe a red blood cell transfusion. Transfusing red blood cells into the patient’s vein raises the percentage of the patient’s blood that consists of red blood cells, increasing the amount of oxygen available to the body.
Vitamin B12 and Folic Acid Supplements
A health care provider may suggest vitamin B12 and folic acid supplements for some people with CKD and anemia. Using vitamin supplements can treat low levels of vitamin B12 or folic acid and help treat anemia. To help ensure coordinated and safe care, people should discuss their use of complementary and alternative medical practices, including their use of dietary supplements, with their health care provider.
Read more about vitamin B12 and folic acid on the MedlinePlus website at www.nlm.nih.gov/medlineplus. Read more about complementary and alternative medicine at www.nccam.nih.gov.
Eating, Diet, and Nutrition
A health care provider may advise people with kidney disease who have anemia caused by iron, vitamin B12, or folic acid deficiencies to include sources of these nutrients in their diets. Some of these foods are high in sodium or phosphorus, which people with CKD should limit in their diet. Before making any dietary changes, people with CKD should talk with their health care provider or with a dietitian who specializes in helping people with kidney disease. A dietitian can help a person plan healthy meals.
Read more about nutrition for people with CKD on the National Kidney Disease Education Program website.
The following chart illustrates some good dietary sources of iron, vitamin B12, and folic acid.
|Recommended Daily Value
|100 percent fortified breakfast cereal
||¾ cup (1 oz)
||1 cup (8 oz)
||1 cup (3 oz)
||1 cup (1 oz)
Points to Remember
- Anemia is a condition in which the body has fewer red blood cells than normal. Red blood cells carry oxygen to tissues and organs throughout the body and enable them to use energy from food.
- Anemia commonly occurs in people with chronic kidney disease (CKD)—the permanent, partial loss of kidney function. Most people who have total loss of kidney function, or kidney failure, have anemia.
- When kidneys are diseased or damaged, they do not make enough erythropoietin (EPO). As a result, the bone marrow makes fewer red blood cells, causing anemia.
- Other common causes of anemia in people with kidney disease include blood loss from hemodialysis and low levels of the following nutrients found in food:
- vitamin B12
- folic acid
- The first step in treating anemia is raising low iron levels.
- If blood tests indicate kidney disease as the most likely cause of anemia, treatment can include injections of a genetically engineered form of EPO.
- Many people with kidney disease need iron supplements and EPO to raise their red blood cell count to a level that will reduce the need for red blood cell transfusions.
- A health care provider may suggest vitamin B12 and folic acid supplements for some people with CKD and anemia.
- A health care provider may advise people with kidney disease who have anemia caused by iron, vitamin B12, or folic acid deficiencies to include sources of these nutrients in their diets.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and other components of the National Institutes of Health (NIH) conduct and support research into many diseases and conditions.
What are clinical trials, and are they right for you?
Clinical trials are part of clinical research and at the heart of all medical advances. Clinical trials look at new ways to prevent, detect, or treat disease. Researchers also use clinical trials to look at other aspects of care, such as improving the quality of life for people with chronic illnesses. Find out if clinical trials are right for you.
What clinical trials are open?
Clinical trials that are currently open and are recruiting can be viewed at www.ClinicalTrials.gov.
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About the Kidney Failure Series
You and your doctor will work together to choose a treatment that's best for you. The publications of the NIDDK Kidney Failure Series can help you learn about the specific issues you will face.
Learning as much as you can about your treatment will help make you an important member of your health care team.
This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.
The NIDDK would like to thank:
John C. Stivelman, M.D., Emory University School of Medicine; Kerri Cavanaugh, M.D., M.H.S., Vanderbilt University
This information is not copyrighted. The NIDDK encourages people to share this content freely.