Iron Deficiency Anemia
What iron deficiency anemia is, which blood tests identify it, and why the cause always needs finding.
Last revised
Too little iron to make enough hemoglobin, so the blood carries less oxygen. It causes fatigue, shortness of breath and poor concentration, and it is a finding rather than a diagnosis: the reason for the deficiency always needs to be established.
The two tests
A complete blood count (CBC) shows hemoglobin and red cell size; in iron deficiency the cells are typically small and pale. Ferritin measures stored iron and falls before hemoglobin does, so it identifies deficiency earlier. Ferritin rises with inflammation, so a normal value in someone with an inflammatory condition does not reliably rule out deficiency, and other tests may be needed.
Why the cause matters more than the number
Iron deficiency has a reason. In women of reproductive age, menstrual blood loss is by far the most common. Otherwise the priority is ruling out bleeding from the digestive tract, which can be the first sign of colorectal cancer. Celiac disease impairs absorption and is commonly tested for. In men, and in women past menopause, unexplained iron deficiency anemia is a recognized reason to examine the digestive tract.
Treatment
Usually oral iron, such as ferrous sulfate, ferrous fumarate or ferrous gluconate. Absorption improves when taken on an empty stomach with a source of vitamin C, and is reduced by tea, coffee, calcium and some medicines. Side effects such as constipation, dark stools and nausea are common; taking it every other day can be as effective and easier to tolerate. Treatment usually continues for some months after hemoglobin returns to normal, to refill iron stores, and your doctor will tell you how long.
Diet alone is rarely enough
Once anemia is established, diet usually cannot correct it quickly enough, which is why supplements are prescribed. Diet matters for prevention and maintenance: heme iron from meat, poultry and seafood is far better absorbed than nonheme iron from beans, lentils, fortified cereals, tofu and leafy greens, which benefit from vitamin C eaten alongside.
At a glance
| Term | Detail |
|---|---|
| Test for stored iron | serum ferritin |
| Test for anemia | complete blood count (CBC), hemoglobin |
| Typical red cell picture | small (low MCV) and pale (low MCH) |
| Most common cause, women of reproductive age | menstrual blood loss |
| Always ruled out in men and postmenopausal women | bleeding from the digestive tract |
| Commonly tested alongside | celiac disease |
| Treatment duration | continues after hemoglobin normalizes, to refill stores |
| Improves absorption | vitamin C; every-other-day dosing often better tolerated |
When to get help
See your doctor for unexplained fatigue with shortness of breath or a racing heartbeat. Iron deficiency in a man, or in a woman past menopause, needs investigation of the digestive tract and should never simply be supplemented. Get urgent care for black, tarry stools or visible blood in the stool, and call 911 for vomiting blood, chest pain, fainting, or shortness of breath at rest.
Where this comes from
- National Heart, Lung, and Blood Institute - Iron-Deficiency Anemia
- MedlinePlus - Iron deficiency anemia
- American Society of Hematology - Anemia
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.
