Feeling tired and short of breath on the stairs can have many causes. One of the most common, and most fixable, is low iron. In adults, though, iron deficiency is a finding that calls for a second question: why is the iron low?

What iron deficiency anemia is

The body needs iron to make hemoglobin, the protein in red blood cells that carries oxygen. When iron runs low, the body makes fewer and smaller red cells. The National Heart, Lung, and Blood Institute calls iron-deficiency anemia the most common type of anemia.

Mild cases often cause no symptoms. As it worsens, people may notice tiredness, shortness of breath, chest pain, headaches or restless legs. Left untreated, the NHLBI notes, it can cause heart problems and make other chronic conditions harder to manage. Chest pain or severe shortness of breath needs emergency care.

Why it happens

The NHLBI lists three broad causes:

  • Blood loss. Heavy menstrual periods, or bleeding in the digestive tract from ulcers, inflammatory bowel disease, polyps or colon cancer. Regular aspirin or NSAIDs such as ibuprofen and naproxen can cause slow bleeding in the stomach or intestines.
  • Poor absorption. Celiac disease, Crohn’s disease, ulcerative colitis, H. pylori infection, and surgery on the stomach or intestines, including weight-loss surgery.
  • Not enough iron in the diet, which is less often the whole story in adults.

Chronic kidney disease and long-term inflammatory conditions such as heart failure can also cause or worsen anemia by changing how the body makes red cells and handles iron.

Finding the cause

Diagnosis starts with blood tests: a complete blood count, hemoglobin, iron levels and ferritin, which reflects the body’s iron stores. The American Gastroenterological Association’s 2020 guideline recommends using a ferritin cutoff of 45 ng/mL rather than 15 to diagnose iron deficiency in people with anemia, since the lower cutoff misses many cases.

For men and for women after menopause, iron deficiency anemia is not considered normal, even without symptoms. The same guideline recommends looking at both ends of the digestive tract, with an upper endoscopy and a colonoscopy, to search for a source of bleeding. It suggests testing for celiac disease, and testing for and treating H. pylori when no other cause is found. Women who still have periods are evaluated case by case. Black or tarry stools, or blood in the stool or vomit, are reasons to be seen right away.

Treatment

Iron pills are the most common treatment, and the NHLBI notes it often takes three to six months to rebuild iron stores, well after the blood count improves. Side effects include constipation, upset stomach, nausea and a metallic taste. Your doctor may suggest taking iron with food, a lower dose, or a different schedule if it disagrees with you. Intravenous iron is more likely to be used for serious deficiency or in people with long-term conditions, and it often restores iron in one or a few sessions.

Food supports treatment but rarely fixes a true deficiency on its own. Good sources include lean red meat, salmon, eggs, beans, peas, tofu, dried fruit, dark leafy greens and fortified cereals. The NIH Office of Dietary Supplements explains that iron from plants is absorbed better when eaten with vitamin C foods such as citrus, strawberries, peppers and tomatoes, while black tea can reduce absorption.

Be careful with iron supplements

Iron is not a supplement to take “just in case.” The NIH recommends 8 mg a day for men and for women 51 and older, and 18 mg for women 19 to 50, with an upper limit of 45 mg a day for adults unless a doctor prescribes more. Too much can cause stomach problems, and people with hereditary hemochromatosis, an inherited iron overload condition, should avoid iron supplements altogether. Iron also interacts with medicines: it can reduce absorption of levothyroxine, our subject in underactive thyroid and the TSH test, and of levodopa, while acid-reducing PPIs can lower iron absorption from food.

Anemia is one of the places where Internal Medicine and kidney care overlap, and as a board-certified internist and nephrologist, Dr. Shtern looks at both. If you take aspirin or an NSAID regularly, our article on NSAID risks is worth a read. Our labs and tests page explains how blood work is handled, and the first visit is a complimentary meet and greet.

This article is general information, not advice for your situation. Members can call the office with questions about their own care.