Signs of iron deficiency

According to the American Society of Hematology, more people are low in iron than any other micronutrient. But many live with fatigue, weakness, brain fog and other symptoms for months or years before a deficiency is detected.

In the United States, nearly a third of adults could suffer from iron deficiency, according to a study in 2024. And routine screening of children and pregnant women – who are at high risk – can go unnoticed in more than 70% of cases.

Some people online self-diagnose, citing dark circles under their eyes and pale skin as evidence of low iron. Social media influencers call this look “ferritin face,” named after a protein that stores this element in the body.

Iron deficiency is common, widespread and underestimated, said Dr. Ariela Marshall, associate professor of medicine at the University of Minnesota. New diagnostic recommendations, released by ASH in September, aim to ensure more patients benefit from early treatment.

The difference between iron deficiency and anemia

Anemia is a disease that occurs when there are not enough red blood cells to carry oxygen to the body’s organs and tissues. Patients with anemia may feel tired, dizzy, or short of breath, and they may have heart palpitations, cold hands and feet, pale skin, brittle nails, or hair loss.

Anemia is often caused by a lack of iron, which supports brain and muscle function and is used to make hemoglobin, the molecule that carries oxygen in the blood. Stored in the protein ferritin, iron is recruited to make hemoglobin in new red blood cells. When ferritin is low, it means there is not enough iron available to make red blood cells, which can lead to anemia.

But iron deficiency can cause the same types of symptoms without affecting hemoglobin or red blood cell counts. Low iron levels can also cause restless legs syndrome and pica, cravings for nonfood items like ice cream or clay. (Doctors don’t know why; it may be a sign that the body is seeking iron from the environment.)

It’s a “common misperception” that iron deficiency without anemia cannot cause symptoms, “and that we definitely need to correct,” Marshall said.

Standard blood tests that count a person’s red blood cell count will not detect an iron deficiency that has not progressed to anemia.

“Symptoms of iron deficiency can be very subtle or attributed to many different things,” said Dr. Jacquelyn Powers, section chief of hematology at Texas Children’s Hospital and lead author of the 2026 guidelines. “Providers don’t always think, ‘Oh, I need to check the iron labs.’ » »

The amount of iron in a person’s blood cannot provide an accurate diagnosis of deficiency because it varies depending on what they have eaten and for how long. Ferritin tests are the gold standard for assessing iron levels, Powers said. But until now, there has been no agreed-upon single outcome threshold for determining who is iron deficient.

The World Health Organization recommends using a ferritin concentration below 15 ng/mL to diagnose iron deficiency in school-aged children and adults. But researchers have questioned those calculations, expressing concern that such a low threshold misses many people whose iron stores are higher than that but still insufficient.

Some blood testing labs use even lower cutoffs, meaning that some patients’ lab tests may come back “normal” even if their ferritin levels are very low.

The new ASH guidelines establish 20 ng/mL or less as the appropriate threshold for children, 30 ng/mL for most adults, and 50 ng/mL or less for those with heavy menstrual bleeding or other risk factors such as a vegan diet or long-term use of antacids for reflux. For adults with inflammatory conditions, the new limit is 100 ng/mL, and the group suggests an additional test, called transferrin saturation.

“One of the goals of the guidelines was to highlight why testing for iron deficiency — whether the patient is anemic or not — is important, because there are interventions you can implement to prevent later complications and treat more subtle symptoms,” Powers said.

People with iron deficiency can experience “a whole range of symptoms, from fatigue to brain fog or blurred thoughts to feeling like you want to chew on things like ice,” Marshall said. “Someone can have all of these. They can have one. They can have none.”

Social media posts claim that signs of iron deficiency, including pale complexion, hair loss and dry skin, can be identified by facial ferritin. But Powers and Marshall were skeptical that low iron could be diagnosed via a selfie.

Although some people on restrictive diets may have trouble getting enough iron each day, Marshall said that’s not usually the cause of a deficiency in the United States. The most common causes are blood loss and digestive disorders.

Women are more likely than men to suffer from iron deficiency due to the blood loss that accompanies menstruation. Women who have heavy periods are particularly sensitive.

Children and pregnant people are also at higher risk of iron deficiency because they use a lot of iron for growth and development. Iron deficiency rates among pregnant women are increasing each trimester, Powers said.

People with chronic gastrointestinal illnesses such as irritable bowel syndrome and celiac disease may not be able to absorb enough iron from their diet. A deficiency can also come from gastrointestinal blood loss, which can be an early sign of colon cancer.

Endurance athletes need more iron than most people and are therefore also more likely to suffer from iron deficiencies. One of the signs of deficiency is not being able to exercise as hard as before.

If a person is eating well, sleeping well and “doing all the things you associate with optimal health, but they’re still very tired, then I think it’s very reasonable to check their ferritin,” Powers said. “It’s an easy test, and there’s an easy intervention.”

Taking iron supplements by mouth can relieve symptoms within a few weeks or months. If this helps you, it means that low iron is contributing to your health problems. But it’s important to work with your doctor to understand why your iron levels were low to begin with, Marshall said.

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