Medically Reviewed by Carol DerSarkissian, MD on November 14, 2022
Written by Stephanie WatsonHave you felt exhausted lately? Can you barely make it up the stairs without getting winded even though you're physically fit? If so, you might be lacking in iron -- especially if you're a woman.
Although many people don't think of iron as being a nutrient, you might be surprised to learn that low iron is the most common nutritional deficiency in the U.S. Almost 10% of women are iron deficient, according to figures from the Centers for Disease Control and Prevention.
Let's look at why iron is so important to your body, what can happen if you're not getting enough of it, and when you need to take an iron supplement.
Iron is an essential mineral. "The major reason we need it is that it helps to transport oxygen throughout the body," says Paul Thomas, EdD, RD, a scientific consultant to the National Institutes of Health, Office of Dietary Supplements.
Iron is an important component of hemoglobin, the substance in red blood cells that carries oxygen from your lungs to transport it throughout your body. Hemoglobin represents about two-thirds of the body’s iron. If you don't have enough iron, your body can't make enough healthy oxygen-carrying red blood cells. A lack of red blood cells is called iron deficiency anemia.
Without healthy red blood cells, your body can't get enough oxygen. "If you're not getting sufficient oxygen in the body, you're going to become fatigued," Thomas says. That exhaustion can affect everything from your brain function to your immune system's ability to fight off infections. If you're pregnant, severe iron deficiency may increase your baby's risk of being born too early, or smaller than normal.
Iron has other important functions, too. "Iron is also necessary to maintain healthy cells, skin, hair, and nails," says Elaine Chottiner, MD, clinical assistant professor and director of General Hematology Clinics at the University of Michigan Medical Center said in an email interview.
How much iron you need each day depends on your age, gender, and overall health.
Infants and toddlers need more iron than adults, in general, because their bodies are growing so quickly. In childhood, boys and girls need the same amount of iron -- 10 milligrams daily from ages 4 to 8, and 8 mg daily from ages 9 to 13.
Starting at adolescence, a woman's daily iron needs increase. Women need more iron because they lose blood each month during their period. That's why women from ages 19 to 50 need to get 18 mg of iron each day, while men the same age can get away with just 8 mg.
After menopause, a woman's iron needs drop as their menstrual cycle ends. After a woman begins menopause, both men and women need the same amount of iron -- 8 mg each day.
You might need more iron, either from dietary sources or from an iron supplement, if you:
If you are a vegetarian or vegan, you may also need to take an iron supplement, because the body doesn't absorb the type of iron found in plants as well as it absorbs the iron from meat.
"People often don't know they have anemia until they have signs or symptoms -- they appear pale or 'sallow,' are fatigued, or have difficulty exercising," Chottiner says.
If you're low in iron, you may also:
If you're tired and dragging, see your doctor. "It's fairly easy to detect and diagnose the different stages of iron deficiency with a simple blood test," Thomas says. Women who are pregnant and people with a gastrointestinal disorder such as Crohn's, ulcerative colitis, or celiac disease should have their iron tested on a regular basis.
If your iron is low, eating a diet that is high in iron-rich foods such as fortified cereals, red meat, dried fruit, and beans may not be enough to give you what you need. Your doctor might recommend that you take an iron supplement.
Prenatal vitamins usually include iron, but not all prenatal vitamins contain the recommended amount. Check with your doctor before taking any supplement.
While you are taking iron supplements, your doctor should test your blood to see if your iron levels have improved.
Iron supplements can cause side effects, usually stomach upset such as nausea, vomiting, diarrhea, dark stools, or constipation. Pregnant women are especially susceptible to constipation. Adding extra fiber to your diet can help relieve this symptom. A stool softener may also make you feel better.
Starting with a low dose of iron and then gradually increasing the dose to the daily recommended amount may help minimize side effects. If your iron supplements are bothering your stomach, your doctor can adjust the dose or form of iron you use. You can also try taking the supplements with food.
Unlike some supplements, when the subject is iron, more is definitely not better. Adults shouldn't take any more than 45 mg of iron a day unless they are being treated with iron under close medical supervision.
For children, iron overdose can be especially toxic. "Iron supplements have killed young children because their needs for iron compared to an adult's are relatively low," Thomas says. If you take iron supplements, it is very important to keep them in a high, locked cabinet, far out of your children's reach. Symptoms of iron poisoning include severe vomiting, diarrhea, abdominal pain, dehydration, and bloody stool in children.
It's difficult for adults to overdose on iron just from food and supplements, because an adult body has systems in place to regulate the amount of iron it absorbs. However, people with the inherited condition hemochromatosis have trouble regulating their iron absorption.
Although most people only absorb about 10% of the iron they consume, people with hemochromatosis absorb up to 30%. As a result, the iron in their body can build up to dangerous levels. That excess iron can deposit in organs such as the liver, heart, and pancreas, which can lead to conditions like cirrhosis, heart failure, and diabetes. For that reason, people with hemochromatosis should not take iron supplements.
