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Side Effects of Iron Tablets

author image Erin Coleman, R.D., L.D.
Erin Coleman is a registered and licensed dietitian. She also holds a Bachelor of Science in dietetics and has extensive experience working as a health writer and health educator. Her articles are published on various health, nutrition and fitness websites.
Side Effects of Iron Tablets
A bottle lid with dark gray capsules in it. Photo Credit: JoyTasa/iStock/Getty Images

Although iron supplementation is sometimes necessary, getting too much iron from tablets causes side effects and can be dangerous. Even taking iron in recommended amounts can create problems. If iron levels in your body are low or you’re at risk of developing an iron deficiency, talk with your healthcare provider about the type of iron tablet that is right for you, and the proper dosage.

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Side Effects

Common side effects of taking iron supplements include constipation, diarrhea, nausea, vomiting and black stools, according to MedlinePlus. A benefit of taking iron tablets instead of liquid iron supplements is that they don’t stain your teeth the way liquid iron supplements can. If constipation occurs from ingesting iron tablets, ask your doctor about using a stool softener. Taking iron tablets with food can help prevent nausea and vomiting.

Symptoms of Overdose

Ingesting too much iron from tablets can lead to iron toxicity, which causes dangerous side effects. An iron overdose can cause liver damage, a metallic taste in your mouth, vomiting blood, bloody stools, dehydration, low blood pressure, a weak pulse, dizziness, chills, fatigue, fever and headache, according to MedlinePlus. Iron toxicity can even cause you to go into shock or a coma.

Recommended Amounts

Many adults can meet their recommended dietary allowance, or RDA, for iron by following a well-balanced diet. The daily RDA for iron is 8 milligrams for men and women over 50, 18 milligrams for women 50 and younger, 27 milligrams for women who are pregnant, and 9 milligrams for breast-feeding women. It’s unlikely that you will ingest too much iron from eating iron-rich foods, but excess iron supplementation can lead to iron toxicity. The tolerable upper intake level, or maximum safe daily dosage, is 45 milligrams of iron.


Some population groups may require iron supplements, including tablets. The Office of Dietary Supplements reports that groups with increased iron needs who may benefit from iron supplementation include pregnant women, teenage girls, women with heavy menstrual losses, people with renal failure, and individuals who don’t absorb iron properly. If you have iron-deficiency anemia, taking iron tablets can bring your iron levels back to normal and get rid of anemia-related side effects, such a fatigue.

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