Iron
Absorbed iron is built into haemoglobin, which red blood cells use to carry oxygen from the lungs to the body.
Full ranking Dose tool Products (3,054)
Key facts
Sources: https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/ · FDA DV 18 mg (https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels); pre-2016 DV [] (https://www.federalregister.gov/documents/2016/05/27/2016-11867/food-labeling-revision-of-the-nutrition-and-supplement-facts-labels); adult UL 45 mg
How it works: How does iron become the ability to carry oxygen?
- Food has two kinds of iron: heme iron in meat is absorbed better; non-heme iron in plants and supplements is absorbed less. Vitamin C increases non-heme iron absorption.
- Iron is absorbed mainly in the duodenum.
- After absorption it binds to transferrin and travels in the blood.
- Most iron is used to make haemoglobin, which carries oxygen from the lungs to tissues.
- Extra iron is stored as ferritin, in the liver and elsewhere.
Schematic only; positions and scale are not anatomical.
Daily dose across products (mg/day)
Label data from official national databases and brand websites, as declared; not lab-verified.
Common forms
Common questions
What is the Daily Value for Iron?
The US FDA Daily Value for adults and children aged 4 and over is 18 mg. It is a labelling reference, not a personal recommendation. [source]
Is there an upper limit for Iron?
The adult Tolerable Upper Intake Level (UL) is 45 mg per day. Going above it long term raises the risk of adverse effects. See the linked source. [source]
How much Iron do products usually contain per day?
As of 2026-11-01, 3,054 products list a comparable daily dose (3,108 dose records; one product can have several). The median is 5 mg per day, and 90% of records fall between 0.43 and 30.9 mg. Figures come from labels and are not lab-tested. [source]
How does iron become the ability to carry oxygen?
Absorbed iron is built into haemoglobin, which red blood cells use to carry oxygen from the lungs to the body. Adult UL: 45 mg per day. Accidental iron overdose can seriously poison children; keep iron products out of their reach. [source]
What are the side effects of Iron?
High-dose iron supplements, especially on an empty stomach, can cause upset stomach, constipation, nausea, abdominal pain, vomiting and diarrhea; large amounts can also inflame the stomach lining, cause ulcers and reduce zinc absorption. (Source: NIH ODS) [source]
What happens if you take too much Iron?
The adult UL is 45 mg a day from all sources. Extremely high doses (hundreds or thousands of mg) can cause organ failure, coma, convulsions and death; accidental overdose of iron products is a leading cause of fatal poisoning in children under 6, so keep them out of reach. People with hereditary hemochromatosis should avoid iron and vitamin C supplements. (Source: NIH ODS) [source]
Is Iron safe during pregnancy and breastfeeding?
The recommended amount in pregnancy is 27 mg a day, with a UL of 45 mg; while breastfeeding it is 10 mg (teens) and 9 mg (women). Too little iron in pregnancy raises the risk of anemia, low birth weight and premature birth; pregnant women should ask their provider and take iron if recommended. (Source: NIH ODS) [source]
Does Iron interact with medications or other supplements?
Iron reduces levodopa absorption and can make levothyroxine less effective. Proton pump inhibitors such as lansoprazole and omeprazole may reduce absorption of nonheme iron from food. Calcium may interfere with iron absorption, so take calcium and iron supplements at different times of day. (Source: NIH ODS) [source]
How and when should you take Iron?
High-dose iron on an empty stomach is more likely to upset the stomach. Eating plant iron with vitamin C foods (citrus, strawberries, sweet peppers, tomatoes, broccoli) or with meat, poultry or seafood improves absorption. Take it at a different time from calcium supplements. (Source: NIH ODS) [source]
Top ranked
| Rank | Brand | Product | Per day | Score |
|---|---|---|---|---|
| 1 | XYMOGEN | Iron Glycinate | 29 mg | 100.0 |
| 2 | The Vitamin Shoppe | Comfort Iron 25 mg | 25 mg | 97.8 |
| 2 | Bayer | Fergon Ferrous Gluconate | 27 mg | 97.8 |
| 2 | The Vitamin Shoppe | Iron 28 mg | 28 mg | 97.8 |
| 5 | Douglas Laboratories | Amino-Iron | 18 mg | 94.4 |