How Much Is Too Much Iron Supplement?

The Iron Disorders Institute indicates that even a mild case of iron toxicity may increase your risk for heart attack, diabetes and cirrhosis of the liver. If left untreated, an iron overload can be fatal. However, your body requires minimum levels of iron to maintain red blood cell production and oxygen transport and to prevent anemia.

Talk to your doctor about the amount of supplemental iron you should be taking. (Image: Seksak Kerdkanno / EyeEm/EyeEm/GettyImages)

For these reasons, it's essential to meet your daily needs for iron and also to stay within the recommended guidelines for iron supplementation to prevent iron toxicity.


Whether there's too much iron in a supplement depends on the type of iron supplement you're taking. The tolerable upper limit set by the Institute of Medicine recommends that you take no more than 45 milligrams of elemental iron a day.

Upper Limits of Iron Intake

According to the Institute of Medicine, most adults can consume up to 45 milligrams of elemental iron daily without toxicity occurring. Your health care provider may recommend a higher dosage, such as 50 to 60 milligrams of iron, to treat iron-deficiency anemia, according to the Office of Dietary Supplements.

Your requirement for iron may also increase slightly if you've recently had surgery or lost blood; if you have a condition that causes malabsorption of nutrients or inflammation in the digestive tract, such as celiac disease or Crohn's disease; or if you have kidney failure. Consult your doctor for proper dosing of iron supplements.

Dosage Based on Type of Iron Supplement

The Office of Dietary Supplements notes that different types of iron supplements contain varying percentages of elemental iron. For this reason, the total milligrams or dosage of an iron supplement you can take before toxicity occurs depends on the form of iron in your supplement. Talk with your heath care provider prior to taking any of these supplements:

Ferrous fumarate supplements contain 33 percent elemental iron. The upper limit of intake for these supplements without a doctor's supervision is 136 milligrams per day, which gives you only 45 milligrams of elemental iron.

Ferrous sulfate supplements contain 20 percent elemental iron, meaning you can take 225 milligrams per day of this form.

Ferrous gluconate contains 12 percent elemental iron, so you can take up to 375 milligrams of this supplement.

Symptoms of Iron Toxicity

Risk for toxicity from iron is relatively high because little iron is excreted from the body. Iron begins to accumulate in body tissues and organs, such as the heart and liver.

Taking iron supplements may cause side effects, such as nausea, vomiting, constipation, diarrhea or abdominal pain, which may or may not be indicators of toxicity. Taking your supplement with food may help to prevent these symptoms.

In addition to gastrointestinal side effects, symptoms of iron toxicity include fluid in your lungs, bloody stool, a metallic taste in your mouth, vomiting blood, dehydration, low blood pressure, chills, coma, convulsions, dizziness, drowsiness, fever, headache, flushing and loss of color in skin.

Go to your local emergency care center if you're experiencing any of these symptoms as iron overload can be fatal.

High Risk for Iron Toxicity

Although iron toxicity can occur in anyone who consumes too many iron supplements or is given too many iron injections, certain people are at higher risk for developing an iron overload.

The Iron Disorders Institute suggests that genetic conditions, such as hemochromatosis and sickle cell disease, may increase your risk of developing iron toxicity. You should also use caution with iron supplements if you're an alcoholic or have a liver disorder.

In addition, most adult men and postmenopausal women require significantly less iron per day than women with menstrual cycles, putting them at risk for toxicity.

If you're on dialysis for kidney failure, your health care provider should monitor your serum iron level and adjust your dosage of iron supplements as needed.

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