Anemia of chronic disease (ACD) is the most common type of anemia in hospitalized patients, accounting for roughly 46% of anemia cases in that setting. It develops when a long-term illness, usually one involving ongoing inflammation, disrupts how your body handles iron and produces red blood cells. Unlike iron deficiency anemia caused by blood loss or poor diet, the problem here isn’t a lack of iron in your body. It’s that your body locks iron away where it can’t be used.
How Inflammation Disrupts Iron
The central player in ACD is a hormone called hepcidin, produced by the liver. When you have a chronic inflammatory condition, your immune system releases signaling molecules that ramp up hepcidin production. Hepcidin then blocks the only doorway iron has to enter your bloodstream: a transporter protein found on the surface of intestinal cells and immune cells called macrophages.
This creates a two-pronged problem. First, your gut absorbs less iron from food. Second, macrophages, which recycle iron from old red blood cells, can no longer release that iron back into circulation. The result is that your blood iron drops even though your total body iron stores may be normal or even high. Your bone marrow, starved of the iron it needs to build new red blood cells, produces fewer of them.
Inflammation also interferes with red blood cell production more directly. Immune signaling molecules like TNF-alpha and interleukin-1 suppress your kidneys’ ability to make erythropoietin, the hormone that tells your bone marrow to produce red blood cells. Those same molecules also make the bone marrow’s red blood cell precursors less responsive to whatever erythropoietin is available. So even when iron does get through, the production line is running slowly.
Conditions That Cause It
ACD develops alongside illnesses that keep the immune system activated over weeks, months, or years. The most common categories include:
- Autoimmune diseases: rheumatoid arthritis, lupus, Crohn’s disease, and ulcerative colitis
- Chronic infections: HIV/AIDS, hepatitis B or C, bone infections (osteomyelitis), bacterial endocarditis, and lung abscesses
- Cancer: particularly lymphoma and Hodgkin disease
- Chronic kidney disease
- Heart failure
The severity of the anemia generally tracks with the severity and duration of the underlying disease. When the inflammation is controlled or the infection is treated, the anemia often improves on its own.
What It Feels Like
ACD is typically mild to moderate, which means symptoms can be subtle and easy to attribute to the underlying illness. Fatigue is the hallmark, often described as a persistent, heavy tiredness that doesn’t improve much with rest. You may also notice shortness of breath during activities that used to feel easy, pale skin, dizziness, or difficulty concentrating. Because many of these overlap with symptoms of the chronic disease itself, the anemia can go unrecognized for a long time.
How It Shows Up on Blood Tests
On a standard blood count, ACD typically shows up as normocytic anemia, meaning red blood cells are normal in size (MCV between 80 and 100 fL) but there aren’t enough of them. In longer-standing cases, the cells can become smaller than normal (microcytic), which is also what happens in iron deficiency anemia. That overlap is where things get tricky diagnostically.
The key difference between ACD and iron deficiency anemia shows up in a few specific lab values:
- Ferritin is the most telling. In iron deficiency, ferritin is low because iron stores are genuinely depleted. In ACD, ferritin is normal or high because iron is trapped in storage, not missing.
- Iron saturation drops below 15% in both conditions, so it can’t distinguish between them on its own.
- Total iron-binding capacity (TIBC) is high in iron deficiency (your body is desperately trying to grab more iron) but normal or low in ACD.
When Both Conditions Overlap
Here’s the complication that makes diagnosis genuinely difficult: many people with chronic inflammatory conditions also develop true iron deficiency on top of ACD. They may have poor appetite, gastrointestinal bleeding from medications, or nutrient absorption problems. When both conditions coexist, the lab picture gets muddled.
The usual ferritin cutoff for iron deficiency (around 30 μg/L) doesn’t work well in people with active inflammation, because inflammation artificially inflates ferritin levels. A 2020 WHO guideline recommends using a higher ferritin threshold of 70 μg/L in patients with elevated inflammatory markers. Research examining bone marrow iron stores in people with chronic inflammatory conditions found that those with true iron deficiency typically had ferritin levels below 200 μg/L and iron saturation below 20%. In heart failure patients specifically, true iron deficiency showed ferritin levels in the range of 44 to 162 μg/L.
Getting this distinction right matters because the treatments are different. Giving iron supplements to someone with pure ACD won’t help much and could be harmful, while withholding iron from someone who genuinely needs it worsens their anemia and quality of life.
How It’s Treated
The most effective treatment for ACD is treating the underlying disease. When inflammation decreases, hepcidin levels drop, iron flows freely again, and red blood cell production recovers. For someone whose rheumatoid arthritis comes under control with treatment, the anemia often resolves without any direct intervention.
When the underlying condition can’t be fully controlled, or when anemia is severe enough to cause significant symptoms, other options come into play. For people with coexisting iron deficiency, intravenous iron is generally preferred over oral supplements, since the gut’s ability to absorb iron is impaired by high hepcidin levels.
Medications that stimulate red blood cell production (erythropoiesis-stimulating agents, or ESAs) are sometimes used, particularly in chronic kidney disease. These work by compensating for the body’s reduced erythropoietin production. However, they carry real risks. Clinical trials have shown higher rates of cardiovascular events, stroke, and death when ESAs are used to push hemoglobin levels above 11 g/dL. Current FDA guidance recommends starting them only when hemoglobin falls below 10 g/dL and using the lowest dose needed to avoid blood transfusions, not to hit a specific target number.
Blood transfusions remain an option for severe, symptomatic anemia that doesn’t respond to other approaches, but they’re reserved for situations where the benefit clearly outweighs the risks of repeated transfusions, including immune sensitization that can complicate future transfusions or organ transplants.
Why It Matters Beyond the Numbers
ACD is easy to dismiss as a secondary concern, something less important than the disease causing it. But the fatigue and reduced exercise capacity it produces have a real impact on quality of life, particularly for people already dealing with a debilitating chronic illness. In hospitalized patients, ACD is associated with longer stays and worse outcomes compared to patients without anemia. Recognizing and addressing it, whether through better control of the underlying disease or targeted treatment of the anemia itself, can meaningfully improve how people feel day to day.