Iron is a mineral that plays a key role in many bodily functions, from forming red blood cells to transporting oxygen and supporting our immune system. It's one of the most important nutrients out there, but many people don't get enough of it.
Iron deficiency, which occurs when iron levels are too low, is not uncommon —it may effect up to 40% of young women in the United States, according to a 2024 study published in JAMA.
Although many foods are rich in the mineral, it can still be difficult to get enough iron, especially if you follow a plant-based diet, menstruate, are pregnant, or donate blood.
That's why iron is a popular supplement, but not everyone needs extra, as too much can do more harm than good. How you take iron supplements can also make a big difference.
So, who needs more iron and when is the best time to take iron supplements? TODAY.com spoke with experts about the benefits, risks and how to take iron pills properly.
What is iron?
Iron is an essential mineral the body needs in certain amounts to function properly. Elemental iron (Fe), is iron in its pure metallic form. Iron is also found in foods, added to fortified food products, and available as a dietary supplement, per the National Institutes of Health’s Office of Dietary Supplements.
The iron in food comes in two forms: heme iron and non-heme iron,Dr. Julia Adamian, an internist at NYU Langone Health, tells TODAY.com.
Heme iron is found in animal products like meat and seafood, and it's more bioavailable, or better absorbed by the body, Adamian says. Non-heme iron is found in plants or iron-fortified foods and is less well absorbed.
Iron supplements, also called iron salts, are chemical compounds containing iron — common forms include ferrous sulfate and ferrous fumarate. Iron is also found in many multivitamins, Elisabetta Politi, a dietitian and diabetes educator at Duke Health, tells TODAY.com.
Iron benefits
Iron benefits our health in numerous ways. Getting enough iron helps with:
- Cell growth and development
- Oxygen transport
- Energy production
- Muscle function
- Immune health
Iron is essential for cellular growth and development, which is why so much of it is needed for a healthy pregnancy and early childhood development, especially of the brain, the experts note.
“Iron contributes to many (enzyme) reactions and metabolites in our body,” says Adamian. These include cellular metabolism and energy production.
Iron is crucial for red blood cell production, says Politi. The body uses iron to make hemoglobin, a protein in red blood cells which transports oxygen from our lungs to the rest of the body. Iron is also used to make myoglobin, a protein in skeletal muscles that stores and releases oxygen, per the NIH.
Additionally, iron plays a role in the production of some hormones, per Medline Plus, and it helps regulate our immune system.
How much iron do you need per day?
The amount of iron you need per day will depend on your age, gender, life stage and diet. According to the NIH, the recommended dietary allowances (RDAs) for iron for non-vegetarians are:
- Men ages 18-50: 8 milligrams
- Women ages 18-50: 18 milligrams
- Pregnant women: 27 milligrams
- Adults ages 51 and over: 8 milligrams
The RDAs for iron for vegetarians are 1.8 times higher, per the NIH, because the non-heme iron in plant foods is harder for the body to absorb, so you need more of it to meet your needs.
Iron gets absorbed in the gastrointestinal tract and most of it goes to the blood. The rest is stored in the liver, spleen, bone marrow and muscles, per the NIH, which the body can use when intake is low.
Who needs an iron supplement?
Most people in the U.S. get enough iron. However, some groups are more likely to have trouble getting enough iron or absorbing it properly, and may benefit from a supplement, per Medline Plus.
Factors that can increase the risk of an iron deficiency include:
- Heavy periods
- Pregnancy
- Certain health conditions
- Gastrointestinal disorders
- Bariatric surgery
- Frequently donating blood
- Strenuous exercise
“One of the most common causes of iron deficiency in reproductive-age women is heavy periods,” says Adamian. Iron is lost through blood during menstruation. Not using hormonal birth control, which often lightens periods, increases the risk, she adds.
Pregnancy can also lower iron levels because it increases maternal blood volume, and the growing fetus and placenta require a significant amount of iron, the experts note.
Certain conditions, including kidney disease, heart disease and cancer, may lower iron levels and lead to a deficiency,says Politi.
Gastrointestinal disorders, such as Crohn's, celiac disease and autoimmune gastritis, can reduce the absorption of iron in the gut, says Adamian. People who've had surgery on their GI tract, such as bariatric surgery, may also have trouble absorbing iron, Politi adds.
Every time you donate blood, the body loses 220-250 milligrams of iron, per the American Red Cross. Food alone may not be enough to replenish the lost iron, especially for frequent donors, says Politi.
Other factors that affect iron levels include a poor diet, certain medications and exercise. "We use iron during strenuous exercise, so exercising a lot can naturally reduce our stores," Adamian adds.
If you have normal iron levels and are not at risk of a deficiency, you do not need a supplement, explains Politi.
Signs of iron deficiency
In the short term, not getting enough iron may not cause obvious symptoms, per the NIH. But over time, low iron levels can lead to a deficiency. Signs of an iron deficiency include:
- Fatigue
- Weakness
- Dizziness
- Decreased exercise tolerance
- Pale skin
- Easy bruising
- Cold hands or feet
- Craving ice
- Restless leg syndrome
Iron deficiency can lead to anemia, a condition that occurs when there are not enough red blood cells or hemoglobin in the body. But “people can be iron deficient with or without anemia,” Adamian clarifies.
If left untreated, anemia can cause serious complications. Always consult your doctor if you have symptoms of an iron deficiency, especially if you're in a high-risk group.
"Blood tests can confirm an iron deficiency, then we recommend supplements or treatments," says Adamian. The experts warn against self-treating a suspected deficiency. "It's really important to diagnose and find the cause first," Politi adds.
Iron supplement dosage
The recommended dosage for iron supplements varies from person to person. The tolerable upper limit for iron, from all sources, is 45 milligrams per day for adults, says Politi.
Your health care provider can help you determine which iron supplement and dosage is right for you.
“It’s definitely important not to be deficient, but ... iron is not something that you want to have in excess,” says Politi.
The best time to take iron supplements
The best time of day to take iron supplements depends on the person and their dosing regimen, but the experts agree that the morning is optimal.
It's often easier to remember to take supplements first thing after waking up. "Right before breakfast can be a good idea, because the stomach has natural acids and iron likes acid for absorption," says Adamian.
Depending on the dosage, iron supplements may be taken once a day, or two to three times a day.
It's also important to consider what else you're taking because iron pills can interact with medications and other supplements, says Politi. These include antacids, certain antibiotics and calcium.
“Take these two hours before or four hours after taking the iron,” says Adamian. Always check with your doctor about interactions before taking iron.
Iron supplements may also be taken every other day, says Adamian, which may be better tolerated for some individuals.
Should you take iron supplements with food?
It's generally recommended to take iron on an empty stomach. “It's better to take (iron) without food, because food can decrease the absorption,” says Adamian.
However, this can also increase the risk of side effects, such as stomach upset. Taking iron pills with a small amount of food may help minimize these effects, the experts note.
Vitamin C can improve the absorption of iron, so consider taking supplements with bell peppers, oranges, strawberries or other fruits high in vitamin C. Avoid taking iron with food or drinks containing milk or caffeine, which can interfere with absorption, Politi adds.
Iron supplement risks and side effects
When taken as directed, iron supplements are usually safe, but they can cause side effects, including:
- Constipation
- Stomach pain
- Nausea
- Vomiting
- Dark stools
These side effects are usually temporary and may resolve over time as your body adjusts to the iron supplements.
High doses of supplemental iron can be harmful and lead to iron overload, says Adamian. This can cause serious problems such as liver damage or organ failure.
"For people who are not iron-deficient, there's no need to take extra iron in a supplement. The risks are greater than the benefits," says Politi.
Food sources of iron
Food is the best source of iron, as there’s minimal risk of getting too much iron from food, says Politi.
Foods rich in iron include:
- Oysters
- Fortified cereals
- Soybeans
- Swiss Chard
- Beef
- White beans
- Lentils
- Spinach
- Tofu
Cooking on an iron skillet can also boost the iron content of foods, says Politi.
