Can Eating Disorders Cause Anemia? The Connection Explained

Eating disorders can and frequently do cause anemia, through several overlapping mechanisms that go well beyond simply not eating enough iron-rich foods. A systematic review pooling data from nine studies found that roughly 45% of people with anorexia nervosa had anemia, making it one of the most common blood-related complications of severe restrictive eating.¹ The connection runs deeper than nutrition alone, involving bone marrow changes, paradoxical shifts in iron metabolism, and a refeeding process that can temporarily make blood counts worse before they get better.

How Common Is Anemia Across Different Eating Disorders

The reported rates vary widely depending on the population studied and how anemia is defined. That roughly 45% figure from the meta-analysis reflects a broad global estimate across studies of anorexia nervosa, but individual studies have found much lower numbers. One study of anorexia patients found that about 17% met the criteria for anemia, with the likelihood tied closely to how long a person had been ill and how severely malnourished they were.² These differences partly reflect who gets studied: people hospitalized with very low body weight tend to have worse blood counts than outpatients at earlier stages of illness.

Anorexia nervosa gets the most research attention, but it is not the only eating disorder linked to anemia. In bulimia nervosa, where people may maintain a more typical weight but engage in binge-purge cycles, about one in five showed signs of mild iron deficiency, and roughly 11% had hemoglobin levels below normal.³ Avoidant/restrictive food intake disorder, sometimes called ARFID, can also lead to iron deficiency anemia, particularly in children and adolescents who eat an extremely narrow range of foods.⁴ Disordered eating habits more broadly, including those that fall short of a formal diagnosis, are recognized as putting people at elevated risk for iron deficiency and eventual anemia.⁵

Why Nutrient Deficiency Alone Does Not Explain It

The most intuitive explanation for anemia in eating disorders is straightforward: if you eat far too little, you do not get enough iron, folate, or vitamin B12 to produce healthy red blood cells. That account is partly right. Case reports in ARFID have documented iron deficiency anemia alongside deficiencies in vitamin K and other nutrients, all traced to a severely limited diet.⁶ But the picture in anorexia nervosa is more complicated, and the evidence here is genuinely surprising.

Studies of people with anorexia have consistently found that serum ferritin, a protein that stores iron, is often elevated rather than depleted. In one study, the median ferritin concentration in anorexia patients was roughly four times higher than in healthy controls.⁷ That same study found that hepcidin, a hormone that regulates how the body absorbs and distributes iron, was also significantly elevated. Normally, high hepcidin signals the body to lock iron away inside cells and reduce absorption from food. In anorexia, this appears to happen even without the inflammation that typically drives hepcidin up. The result is a paradox: the body has iron in storage, but it cannot effectively use that iron to make red blood cells. Some patients have been reported with extremely high ferritin levels, representing the most extreme end of this perturbed iron metabolism.⁸

Vitamin B12 tells a similarly counterintuitive story. A cross-sectional study of anorexia patients found that excessively high B12 levels were far more common than deficiency, with elevated concentrations correlating with markers of liver stress.⁹ The likely explanation is that the liver, itself damaged by starvation, releases stored B12 into the bloodstream. This means a clinician who sees a normal or high B12 level might wrongly assume the patient’s nutritional status is fine.

What Starvation Does to Bone Marrow

Beyond nutrient supply, prolonged malnutrition can damage the factory where blood cells are made. In healthy bone marrow, stem cells divide and mature into red blood cells, white blood cells, and platelets. In severe starvation, the fat and cell-producing tissue in bone marrow can be replaced by a gelatinous substance, a condition pathologists call gelatinous transformation of bone marrow, or sometimes “starvation marrow.” This transformation involves the marrow becoming hypoplastic, meaning it produces fewer blood cells, with the normal fat tissue atrophying and being replaced by a gelatinous infiltrate.¹⁰

This marrow change is not specific to eating disorders. It shows up in other conditions involving severe illness and poor nutrition. But eating disorders, especially anorexia nervosa, are among the most commonly reported causes. The practical consequence is that the anemia seen in severe eating disorders is not always the iron-deficiency type that responds to supplements. When the bone marrow itself is compromised, the body cannot produce enough blood cells regardless of whether nutrients are available. Fortunately, this transformation is generally reversible with adequate nutritional rehabilitation, and one study found that 89% of patients with severe anorexia resolved their white blood cell deficiencies by hospital discharge once refeeding was underway.¹¹

The Refeeding Paradox

One of the most unsettling aspects of the eating disorder-anemia connection is that blood counts frequently get worse before they get better when treatment begins. During the early days of refeeding in hospitalized anorexia patients, hemoglobin dropped by about 22%, white blood cell counts fell by roughly a third, and platelet counts declined by about a quarter. All of these reached their lowest points between the fifth and tenth day of hospital refeeding.¹²

Why would feeding someone make their blood counts drop? Part of the explanation involves bone marrow fat. During early weight recovery, the fat in bone marrow may actually increase along with body fat elsewhere, temporarily compressing the space where stem cells need to proliferate. This delays the expected recovery of blood cell production even as overall nutrition improves.¹³ Another factor is dilution: starvation concentrates the blood through dehydration, and once a patient begins receiving fluids and food, the plasma volume expands, making hemoglobin appear to drop even before any true change in red blood cell production.

This refeeding dip is a major reason why eating disorder treatment requires close medical monitoring. The goal is proper nutritional rehabilitation, but clinicians need to watch blood counts carefully during that critical first week or two.

When Lab Values Hide the Problem

Dehydration and starvation conservation mechanisms can create misleadingly normal lab results in people with active eating disorders. When the body is severely dehydrated, the blood becomes more concentrated, which can push hemoglobin readings into what looks like the normal range. Similarly, certain micronutrients may appear adequate on a blood test because the body has shifted to survival-mode distribution, keeping circulating levels up even as true stores are depleted. These artificially maintained values can then crash once rehydration and refeeding begin.¹⁴

The elevated ferritin and hepcidin levels discussed earlier add another layer of confusion. A clinician unfamiliar with this pattern might see high ferritin and conclude the patient has plenty of iron, when in reality the iron is locked away and unavailable for blood cell production. Electrolyte levels need equally close monitoring during treatment, because depleted stores require longer supplementation than a short-term dietary gap would.¹⁴ All of this means that a standard blood panel can falsely reassure both patients and providers, especially early in the course of illness.

Bulimia and Purging Behaviors

The link between anorexia and anemia gets more attention, but bulimia nervosa has its own distinct pathways to low blood counts. People with bulimia may eat substantial amounts during binge episodes, potentially consuming enough iron and other nutrients in those meals. But the compensatory behaviors that follow, including vomiting, laxative misuse, and extended fasting, undermine absorption and increase losses. Repeated vomiting can irritate or tear the esophageal and gastric lining, causing chronic low-grade blood loss that adds up over time.

The study of women with bulimia nervosa found that nearly one in five had elevated transferrin values suggesting mild iron deficiency, and about 5% had low vitamin B12.³ Interestingly, the women who did have low hemoglobin or low B12 were not distinguishable from other bulimia patients by body weight, binge frequency, or vomiting frequency. In other words, you cannot predict who will develop anemia just by looking at their weight or their reported behaviors, which makes screening all the more important.

Pica and the Iron Deficiency Loop

Pica, the persistent craving and consumption of non-food substances like ice, clay, starch, or paper, is classified as a feeding and eating disorder in its own right. It has a well-documented relationship with iron deficiency anemia, though researchers continue to debate which way the causation runs. A meta-analysis covering more than 16,000 individuals found that people with pica had about 2.4 times greater odds of anemia compared to those without it.¹⁵

Some researchers believe that eating non-food substances displaces nutritious food or actively interferes with iron absorption. Others argue the opposite: that iron deficiency itself triggers the cravings, and pica is a symptom rather than a cause. The clinical reality is probably a self-reinforcing cycle. A person with marginal iron status develops pica cravings, the pica further reduces iron intake or absorption, and the worsening deficiency intensifies the cravings. Treating the iron deficiency often resolves the pica behaviors, which supports the idea that the deficiency drives the behavior at least in part.

When Eating Disorders Collide with Pre-Existing Conditions

Eating disorders do not occur in a vacuum. When someone with a pre-existing blood disorder develops an eating disorder, the combination can be dangerous in ways neither condition would produce alone. One reported case involved an adolescent girl with hereditary spherocytosis, a condition where red blood cells are unusually fragile. Her anorexia nervosa and the resulting severe malnutrition triggered life-threatening complications of her inherited anemia, complications that had been manageable before the eating disorder began.¹⁶

This kind of interaction is worth knowing about because eating disorders are underdiagnosed, and patients with chronic conditions sometimes restrict food for reasons that blend medical anxiety with disordered eating. The combination of a hemolytic condition (where red blood cells break down faster than usual) with the impaired blood cell production caused by starvation creates a double hit that can spiral quickly. Anyone managing a known blood disorder who also struggles with eating patterns should be particularly aware of the risks.

Bariatric Surgery and Overlapping Risk

Bariatric surgery and eating disorders share an underappreciated overlap. Some people who undergo weight-loss surgery have pre-existing or develop post-surgical disordered eating patterns, and all bariatric procedures alter the digestive tract in ways that increase vulnerability to nutrient deficiencies. Anemia is one of the most common long-term nutritional complications after bariatric surgery, largely because the surgical changes reduce the body’s ability to absorb iron and other nutrients from food.¹⁷ Adding disordered eating on top of already-reduced absorption capacity compounds the problem. Many patients who are obese already have iron deficiency before surgery, so the starting point is often worse than assumed.

What Recovery Looks Like for Blood Counts

The encouraging part of this picture is that anemia caused by eating disorders is generally reversible. Once nutritional rehabilitation is underway and sustained, the bone marrow recovers its ability to produce blood cells. As mentioned, the majority of hospitalized anorexia patients saw their blood count abnormalities resolve by discharge.¹¹ But “by discharge” can mean weeks, and the initial worsening during refeeding can be alarming for patients and families who expect improvement from day one.

Full bone marrow recovery takes longer than the blood counts alone suggest. Even after hemoglobin normalizes, the underlying marrow architecture may still be rebuilding. Depleted nutrient stores, particularly iron, can take months of adequate intake to fully replenish, and patients with eating disorders are unlikely to immediately maintain the kind of diet that would accomplish this on its own. Supplementation during and after treatment is often necessary, tailored to the specific deficiencies identified through blood work rather than given as a blanket one-size-fits-all approach.¹⁴

The trajectory is not always linear. Setbacks in the eating disorder can reverse hematological gains. Patients who relapse into restriction after partial recovery may see their blood counts deteriorate again, sometimes faster than the first time because their reserves are already thin. Long-term recovery from the anemia ultimately depends on sustained recovery from the eating disorder itself, which is why hematological monitoring is a standard part of ongoing care for people in treatment.