Iron deficiency is the most common nutritional deficiency in the world. When the body does not have enough iron, it cannot make enough healthy red blood cells, leading to iron deficiency anemia. The result is often tiredness that sleep does not fix. Here is how to recognize the signs, understand your blood tests and restore your iron safely.
Why your body needs iron
Iron is a key part of hemoglobin, the protein in red blood cells that carries oxygen from your lungs to the rest of your body. Iron is also needed for muscle function, brain development and a healthy immune system. When iron stores run low, oxygen delivery suffers.
Symptoms of iron deficiency anemia
Mild iron deficiency may cause no symptoms. As it progresses, you may notice:
- Fatigue and weakness
- Pale skin, or paleness inside the lower eyelids
- Shortness of breath or a racing heart with exercise
- Dizziness or lightheadedness
- Headaches
- Cold hands and feet
- Brittle nails or spoon-shaped nails
- Hair thinning
- A sore or smooth tongue, or cracks at the corners of the mouth
- Restless legs at night
- Pica: unusual cravings for ice, clay, dirt or starch
Common causes
Blood loss
- Heavy menstrual periods, one of the most common causes in women
- Bleeding in the digestive tract, from ulcers, hemorrhoids, polyps, inflammatory bowel disease or colorectal cancer
- Regular use of aspirin or other NSAIDs, which can irritate the stomach
- Frequent blood donation
Not getting enough iron
- Diets low in iron, including some vegetarian and vegan diets that are not well planned
Increased need
- Pregnancy
- Rapid growth in infants, children and teenagers
Poor absorption
- Celiac disease
- Weight-loss surgery
- Long-term use of acid-reducing medicines
In adult men and postmenopausal women, iron deficiency should always prompt a search for a source of blood loss, especially from the digestive tract.
How iron deficiency is diagnosed
A simple set of blood tests usually confirms the diagnosis:
- Complete blood count (CBC): measures hemoglobin and red blood cell size. Iron deficiency typically causes small, pale red cells.
- Ferritin: reflects your iron stores. A low ferritin level is the most specific sign of iron deficiency. Many clinicians use a level below about 30 ng/mL as a sign of low iron stores in adults, although laboratory ranges vary.
- Serum iron, transferrin saturation and total iron-binding capacity add further detail.
The World Health Organization defines anemia in adults as a hemoglobin level below:
| Group | Hemoglobin threshold |
|---|---|
| Men (15 years and older) | 13.0 g/dL |
| Non-pregnant women (15 years and older) | 12.0 g/dL |
| Pregnant women | 11.0 g/dL |
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Ferritin can rise during infection or inflammation, so a “normal” level does not always rule out iron deficiency in those situations.
How much iron do you need?
The Recommended Dietary Allowance for adults in the United States is:
| Group | Daily iron |
|---|---|
| Men 19 and older | 8 mg |
| Women 19–50 | 18 mg |
| Women 51 and older | 8 mg |
| Pregnancy | 27 mg |
| Breastfeeding | 9–10 mg |
Vegetarians may need up to 1.8 times more iron because plant iron is less easily absorbed. See the NIH Office of Dietary Supplements iron fact sheet for details.
Best food sources of iron
Heme iron (more easily absorbed)
- Lean red meat
- Poultry
- Fish and shellfish, such as clams, oysters and sardines
Non-heme iron (from plants and fortified foods)
- Fortified breakfast cereals
- Beans, lentils and chickpeas
- Tofu
- Spinach and other leafy greens
- Pumpkin seeds
- Dried apricots and raisins
Boost absorption
- Pair plant iron with vitamin C: citrus fruits, strawberries, tomatoes, bell peppers or broccoli.
- Avoid drinking tea or coffee with iron-rich meals; they reduce absorption.
- Calcium can also reduce absorption, so separate calcium supplements from iron.
Treatment
Iron supplements
Oral iron, such as ferrous sulfate, is the usual first treatment. Your clinician will suggest a dose. Research shows that taking iron once a day or every other day can be as effective as taking it several times a day and may cause fewer side effects, because the body absorbs less iron immediately after a dose.
Common side effects include constipation, nausea, stomach upset and dark stools. Taking iron with a small amount of food can help, though it slightly lowers absorption.
Hemoglobin often begins to rise within a few weeks. Treatment usually continues for about three months after levels normalize to rebuild iron stores.
Intravenous iron
IV iron may be recommended if you cannot tolerate or absorb oral iron, have ongoing blood loss, have severe anemia, have chronic kidney disease or inflammatory bowel disease, or are in later pregnancy.
Treating the cause
Finding and treating the reason for iron loss, such as heavy periods or a digestive problem, is essential.
Safety warning
Do not take iron supplements without a confirmed need, as too much iron can be harmful. Keep iron tablets out of reach of children; iron overdose is a dangerous cause of poisoning in young children.
Frequently asked questions
How long does it take to feel better?
Many people feel more energetic within a few weeks of starting treatment, but it takes several months to fully rebuild iron stores.
Can you have low iron without anemia?
Yes. Iron stores (ferritin) can be low before hemoglobin falls. This can still cause fatigue and other symptoms.
Is iron deficiency serious?
Untreated, it can cause significant fatigue, heart strain and complications in pregnancy. It can also be a sign of an underlying condition that needs attention.
The bottom line
Iron deficiency anemia is common, especially in women, and often causes persistent tiredness. A blood test that includes ferritin can confirm it. Iron-rich foods, the right supplement and treating the cause usually restore your levels.
This article is for general information and is not a substitute for advice from a qualified healthcare professional.