Anemia occurs when your red blood cells are in short supply. It can lead to symptoms such as fatigue.

Anemia is a common problem in people with chronic kidney disease (CKD). Anemia becomes more common with increasing severity of CKD. It occurs in less than one in five people with mild CKD, but almost two-thirds of those with advanced CKD experience anemia.

Anemia is easily diagnosed using a blood test that measures hemoglobin. If you have mild CKD, you should have your blood screened for anemia every year. Your blood work should be checked more frequently if you have advanced CKD or if you’ve already been diagnosed with anemia.

After an anemia diagnosis, your doctor should perform a thorough evaluation to identify what’s causing it. This includes a complete blood count, studies of iron levels, and other tests, depending on the clinical situation.

Iron deficiency is a common and treatable cause of anemia in CKD. About half of those with CKD have low iron levels on their blood tests. People with CKD also require slightly higher iron levels to make red blood cells.

People with CKD are at an increased risk for anemia because they’re unable to produce the hormone erythropoietin that stimulates production of red blood cells.

People with CKD also tend to experience blood loss and have difficulty absorbing iron from their gut. In addition, those with advanced CKD who require hemodialysis also lose blood during their dialysis treatment.

If your blood work shows that you have iron deficiency, your doctor will prescribe a trial of iron supplements either through pills or injection.

Iron pills are inexpensive and easy to take, but they’re limited by gastrointestinal side effects and poor absorption.

If iron pills fail to improve your hemoglobin levels, your doctor might prescribe iron through an injection.

Iron injections are safe and well tolerated. Some older forms of iron injection (called “iron dextran”) came with an increased risk for allergic reactions. But this happens very rarely with the newer forms currently used.

If you’re already on dialysis, you’re usually prescribed iron through an injection. In fact, more than half of those on hemodialysis require regular iron injections.

If iron supplements (either by pills or injection) don’t sufficiently increase your hemoglobin levels, your doctor will prescribe injectable hormones to stimulate red blood cell production. That includes drugs such as darbepoetin and epoetin.

These therapies are generally not started until the hemoglobin falls below 10 grams per deciliter (g/dL). Most people with CKD are given these injections under their skin. If you’re receiving hemodialysis, these drugs are administered during dialysis treatment.

Iron supplementation is continued during treatment with these hormones.

The biggest risk of using hormones to treat anemia is that they might lead to an increased risk for stroke.

This risk increases with higher levels of hemoglobin — even at levels considered normal in people without CKD. Therefore, hormones are used to maintain a level of just enough hemoglobin to avoid the need for blood transfusions and minimize symptoms.

The second risk is in people with cancer, as these drugs could worsen their cancer. In those cases, these drugs are either avoided or used very carefully, particularly if a cure is anticipated.

Anemia treatment can improve symptoms such as fatigue. It can also reduce the need for blood transfusions. Repeated blood transfusions can make it difficult to find a match for kidney transplantation.

With good anemia management, the majority of people with CKD don’t require blood transfusions except in pressing situations such as blood loss, urgent heart issues, or during surgery.

Many people are surprised to learn that they have kidney disease even though they’re still producing urine. In fact, people with CKD and even those on dialysis often continue to make a lot of urine.

There’s a difference between producing urine and having optimal kidney function. Even people with advanced CKD continue to make urine. But their kidneys can’t perform other crucial functions such as clearing waste products, balancing electrolytes, and producing the hormone needed to make red blood cells.

In fact, since people with CKD often require water pills to maintain a healthy blood pressure, they may even experience increased urine output.

Dennis Moledina, MBBS, PhD, a Yale Medicine nephrologist and assistant professor at Yale School of Medicine, is a board-certified nephrologist and clinical researcher at the Clinical and Translational Research Accelerator in the Department of Internal Medicine. He completed a clinical and post-doctoral fellowship in Nephrology at Yale and earned his doctorate degree from the Yale Graduate School of Arts and Sciences (Investigative Medicine Program). He is currently evaluating biomarkers for acute interstitial nephritis and acute kidney injury, enrolling patients in NIH-funded cohorts including Kidney Precision Medicine Program, and directs the Yale Kidney BioBank.