Background

Iron is a mineral. Most of the iron in the body is found in red blood cells and muscle cells. Food sources include meat, fish, beans, spinach, and cereal.

Iron helps red blood cells carry oxygen from the lungs to cells all over the body. Iron also plays a role in many important functions in the body.

People commonly use iron for preventing and treating different types of anemia caused by low iron levels. It is also used for ADHD, child development, fatigue, and many other conditions, but there is no good scientific evidence to support most of these other uses.

Safety Safety definitions

When taken by mouth: Iron is likely safe for most people when used in doses below the tolerable upper intake level (UL) of 45 mg elemental iron daily. It can cause side effects such as stomach upset, nausea, and vomiting. Taking iron supplements with food seems to reduce side effects. But food can also reduce how well the body absorbs iron. Doses above the UL should only be used while under medical supervision. Iron is likely unsafe when taken in excessive doses.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Iron is likely safe to use while pregnant and breast-feeding in doses below the UL of 45 mg of elemental iron by mouth daily. But iron is likely unsafe when taken by mouth in high doses. If you do not have iron deficiency, don't take more than 45 mg daily. Higher doses can cause stomach side effects such as nausea and vomiting and may even increase the risk for preterm birth.

Children: Iron is likely safe when taken by mouth in doses below the UL of 40 mg of elemental iron daily. But high doses of iron are likely unsafe for children. Iron is the most common cause of poisoning deaths in children. Doses as low as 60 mg/kg can be fatal.

Diabetes: High iron intake in the diet might increase the risk of heart disease in females with type 2 diabetes. If you have diabetes, discuss your iron intake with your healthcare provider.

Hemodialysis: Iron from supplements might not be absorbed well in people on hemodialysis.

Hemoglobin diseases: Taking iron might cause iron overload in people with these conditions. If you have a hemoglobin disease, do not take iron unless directed by your healthcare provider.

An inherited disorder that affects the formation of blood vessels (hereditary hemorrhagic telangiectasia or HHT): Taking iron might increase the risk of nosebleed in patients with HHT. Use with caution.

Premature infants: Giving iron to premature infants with low blood levels of vitamin E can cause serious problems. Low levels of vitamin E should be treated before giving iron. Talk with your healthcare provider before giving iron to a premature infant.

Physical training: Iron might not be absorbed as well in young females participating in physical training.

A sudden injury that causes damage to the brain (traumatic brain injury): Iron might worsen swelling of the brain in people with recent brain damage due to injury.

Effectiveness

Dosing & administration

Iron is found in many foods, including beef, liver, lamb, pork, ham, chicken, fish, spinach, and beans. The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). For males 19 years and older and females 51 years and older, the RDA is 8 mg. For females 19-50 years of age, the RDA is 18 mg. While pregnant, the RDA is 27 mg. While breast-feeding, the RDA is 10 mg for those 14-18 years of age, and 9 mg for those 19-50 years of age. In children, the RDA depends on age. Don't take more than 45 mg iron daily unless under the supervision of a healthcare provider. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.

Interactions with pharmaceuticals

Antibiotics (Quinolone antibiotics)

Interaction Rating=Moderate Be cautious with this combination.

Iron can decrease how much quinolone antibiotic the body absorbs from the stomach. Taking iron along with these antibiotics might decrease the effects of these antibiotics. To avoid this interaction, take iron 2 hours before or 2 hours after taking antibiotics.

Antibiotics (Tetracycline antibiotics)

Interaction Rating=Moderate Be cautious with this combination.

Iron might decrease how much tetracycline antibiotics the body can absorb from the stomach. Taking iron along with these antibiotics might decrease the effects of these antibiotics. To avoid this interaction, take iron 2 hours before or 4 hours after taking tetracyclines.

Bictegravir/Emtricitabine/Tenofovir Alafenamide (Biktarvy)

Interaction Rating=Moderate Be cautious with this combination.

Iron can decrease how much bictegravir/emtricitabine/tenofovir alafenamide the body absorbs from the stomach. To avoid this interaction, take iron and bictegravir/emtricitabine/tenofovir alafenamide with food. Do not take bictegravir/emtricitabine/tenofovir alafenamide on an empty stomach with, or 2 hours after, iron containing products.

Bisphosphonates

Interaction Rating=Moderate Be cautious with this combination.

Iron can decrease how much bisphosphonate the body absorbs from the stomach. Taking iron along with bisphosphonate can decrease the effects of bisphosphonate. To avoid this interaction, take bisphosphonate at least two hours before iron or later in the day.

Chloramphenicol

Interaction Rating=Minor Be watchful with this combination.

Iron is important for producing new blood cells. Chloramphenicol might decrease new blood cells. Taking chloramphenicol for a long time might decrease the effects of iron on new blood cells. But most people only take chloramphenicol for a short time so this interaction isn't a big problem.

Denosumab (Prolia, others)

Interaction Rating=Moderate Be cautious with this combination.

Denosumab is a drug used for weak and brittle bones (osteoporosis). It is given by IV. Both iron, when given by IV, and denosumab can lower levels of phosphate and calcium in the blood. Use within weeks of each other might cause phosphate and calcium levels to drop too low and cause serious side effects.

Dolutegravir (Tivicay)

Interaction Rating=Moderate Be cautious with this combination.

Dolutegravir is a drug used for HIV infection. Iron can reduce how much dolutegravir the body absorbs from the stomach. To avoid this interaction, take dolutegravir at least 2 hours before or 6 hours after taking iron.

Levodopa

Interaction Rating=Moderate Be cautious with this combination.

Iron might decrease how much levodopa the body absorbs. Taking iron along with levodopa might decrease the effects of levodopa. Do not take iron and levodopa at the same time.

Levothyroxine (Synthroid, others)

Interaction Rating=Moderate Be cautious with this combination.

Levothyroxine is used for low thyroid function. Iron can decrease how much levothyroxine the body absorbs. Taking iron along with levothyroxine might decrease the effects of levothyroxine.

Medications for HIV/AIDS (Integrase inhibitors)

Interaction Rating=Moderate Be cautious with this combination.

Taking iron along with integrase inhibitors might decrease blood levels of these drugs. This might decrease their effects. Talk to your healthcare provider if you are using integrase inhibitors and want to start taking iron.

Methyldopa (Aldomet)

Interaction Rating=Moderate Be cautious with this combination.

Iron can decrease how much methyldopa the body absorbs. Taking iron along with methyldopa might decrease the effects of methyldopa. To prevent this interaction, take iron at least two hours before or after taking methyldopa.

Mycophenolate mofetil (CellCept)

Interaction Rating=Moderate Be cautious with this combination.

Iron might decrease how much mycophenolate mofetil the body absorbs. Taking iron along with mycophenolate mofetil might decrease the effects of mycophenolate mofetil. But it's not clear if this is a big concern. Until more is known, take iron at least 4 hours before, or 2 hours after taking mycophenolate mofetil.

Penicillamine (Cuprimine, Depen)

Interaction Rating=Moderate Be cautious with this combination.

Iron might decrease how much penicillamine the body absorbs. This might decrease the effects of penicillamine. To avoid this interaction, take iron 2 hours before or 2 hours after taking penicillamine.

Interactions with herbs & supplements

Beta-carotene: Beta-carotene may help the body absorb iron from wheat, corn flour, and rice products that contain added iron. But taking extra beta-carotene probably isn't helpful for people who have normal levels of beta-carotene.
Calcium: Calcium makes it harder for the body to absorb iron from food or supplements. In people who have enough stored iron, this isn't a big concern. But if you are iron deficient or might become iron deficient, don't take calcium supplements at mealtime or when you take iron supplements.
Gum Arabic: Gum Arabic forms an insoluble gel with some forms of iron. It isn't known whether this leads to a significant interaction when the two are ingested together.
Lactobacillus: A probiotic species called Lactobacillus plantarum might increase how much iron the body can absorb.
Soy: Soy protein seems to reduce the body's ability to absorb iron. If you have low iron levels, choose fermented soy products like tempeh, which might not have the same effect.
Vitamin A: Taking vitamin A supplements seems to improve iron levels in people whose vitamin A and iron levels are too low. But taking extra vitamin A probably isn't helpful for people who have normal levels of vitamin A.
Vitamin C: Taking vitamin C with iron-containing foods helps the body absorb the iron. It doesn't matter whether the vitamin C comes from food or a supplement. But taking vitamin C doesn't seem to affect how much iron the body absorbs from iron supplements.
Zinc: Iron can interfere with how the body absorbs zinc, and vice versa. But food stops the interaction. To get maximum benefit from zinc or iron supplements, it's a good idea to take them with food.

Interactions with foods

Taking iron with food can decrease how much iron is absorbed by the body by 40% to 75%. For best absorption, iron should be taken on an empty stomach. Some people might not be able to tolerate this because it can cause side effects such as nausea. If iron needs to be taken with food, avoid dairy foods, coffee, tea, and cereals.