You may take iron pills to treat iron-deficiency anemia or to supplement low iron in your diet. The recommended maximum iron intake is 45 milligrams per day in healthy adults, and taking more than that can cause side effects or an overdose.
Most healthy adults can safely take 45 milligrams per day of elemental iron.
Why Take Iron Pills?
Iron is a necessary mineral that helps your body create hemoglobin, a substance inside red blood cells that aids with storing and transporting oxygen around your body. Iron is also used for creating DNA, energy production and cell growth.
- 11 milligrams for men ages 14 to 18
- 15 milligrams for women ages 14 to 18
- 8 milligrams for men ages 19 to 50
- 18 milligrams for women ages 19 to 50
- 27 milligrams for pregnant people
- 9 to 10 milligrams for breastfeeding people* 8 milligrams for adults over 51 years of age
Your doctor may recommend iron pills if you have iron-deficiency anemia, a condition where a lack of iron affects the ability of your red blood cells to transport oxygen. You typically have to take iron pills for weeks or months to restore your iron levels, and common side effects of iron supplements include diarrhea, nausea and constipation.
According to the American Society of Hematology, people at an increased risk for iron-deficiency anemia include:
- Anyone pregnant or breastfeeding, or who has recently given birth
- People with heavy menstrual periods
- Vegetarians or vegans who don't eat enough iron-rich foods
- Anyone who has undergone major surgery or a physical trauma
- People with gastrointestinal conditions that affect nutrient absorption, such as celiac disease, Crohn's disease, peptic ulcer disease and ulcerative colitis
- People who have undergone bariatric procedures like a gastric bypass operation
There are a number of symptoms of iron-deficiency anemia, including:
- Shortness of breath
- Looking pale or having "sallow" skin
- An increased heart rate
- Pica, characterized by craving nonfood items like ice or dirt
- A sore or swollen tongue
- Generally feeling weak
- Brittle nails
- Hair loss
Your doctor can check you for iron-deficiency anemia through a blood test. If you do have the condition, treatment options include increasing your dietary iron intake, taking high-dose iron tablets or taking intravenous iron.
Iron in Food
You may be able to increase your iron levels through your diet rather than by taking iron pills, depending on what your doctor recommends. Iron-rich foods contain heme or nonheme iron. Heme iron, found in animal foods, is more easily absorbed by your body than the nonheme iron found in plant foods. That explains why vegetarians and vegans are at a higher risk of iron deficiency than people who eat meat.
The Mayo Clinic lists eggs, meat, leafy green vegetables and iron-fortified foods as examples of iron-rich foods.
Foods that inhibit iron absorption include caffeine, antacids and calcium supplements.
Maximum Iron Intake
The tolerable upper intake level (UL) for iron is 45 milligrams per day in adults over age 19. The UL is also 45 milligrams per day for lactating or breastfeeding people. In children and adolescents, the UL is 40 milligrams per day for ages 0 to 13, and 45 milligrams per day for ages 14 to 18. Intake levels higher than that can result in side effects or an iron overdose.
However, these numbers don't apply to everyone. In its series on dietary reference intakes, the National Academy of Sciences explains that certain conditions make people "susceptible to the adverse effects of excess iron intake," including trouble processing iron, chronic alcoholism, alcoholic cirrhosis, liver diseases, genetic iron overload and blood disorders like thalassemia that affect hemoglobin levels.
The maximum iron intake of those individuals will be lower, and anyone with those conditions should consult his doctor before taking high dose iron tablets or supplemental iron pills of any kind.
High-Dose Iron Tablets
Some iron supplements may contain numbers higher than the recommended maximum amount of iron per day. That's because your body doesn't absorb 100 percent of the iron contained in a supplement or food.
The amount of iron your body absorbs from a supplement, known as "elemental iron," depends on the form of iron. As outlined by the National Institutes of Health Office of Dietary Supplements:
- Ferrous fumarate supplements contain 33 percent elemental iron
- Ferrous sulfate supplements contain 20 percent elemental iron
- Ferrous gluconate supplements contain 12 percent elemental iron
Symptoms of Iron Toxicity
If you take too many high-dose iron tablets in a short period of time, you may experience an iron overdose. Iron overdoses are especially serious in children, who might be tempted by bright-colored iron pills or gummy vitamins containing iron.
- Stage 1 symptoms, within six hours of the overdose, include vomiting, diarrhea, stomach pain, vomiting blood, drowsiness and feeling irritable. In serious overdose cases, you might also see symptoms of low blood pressure, increased heart rate, fast breathing, seizures, unconsciousness and coma.
- Stage 2, at six to 48 hours after the overdose, might look like a person's condition is improving.
- Stage 3 symptoms, 12 to 48 hours after the overdose, can include bleeding, going into shock (very low blood pressure), seizures, jaundice, fever, liver failure and metabolic acidosis (an abnormally low blood pH).
- Stage 4, which is two to five days after the overdose, involves symptoms that include liver failure, decreased blood sugar levels, confusion, lethargy and coma. "People may die from shock, bleeding, and blood-clotting abnormalities," Merck says.
- Stage 5, two to five weeks after the overdose, can show scarring, blocking the stomach or intestines, which may cause vomiting and abdominal pain. Later on, scarring of the liver (cirrhosis) can develop.
- MedLinePlus: "Iron Overdose"
- Merck Manual: "Iron Poisoning"
- National Academy of Sciences: "Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc"
- National Institutes of Health: Office of Dietary Supplements: "Iron"
- American Society of Hematology: "Iron-Deficiency Anemia"
- Mayo Clinic: "Iron Deficiency Anemia"
- USDA: "Cereals Ready-to-eat, Ralston Enriched Wheat Bran Flakes"
- USDA National Nutrients Database: "Chicken, Liver, All Classes, Cooked, Pan-fried"
- USDA National Nutrient Database: "Beef, Variety Meats and By-products, Liver, Cooked, Braised"
- USDA National Nutrient Database: "Spinach, Raw"
- Oregon State University: Linus Pauling Institute: "Iron"