ABOUT IRON SUPPLEMENTS

Iron supplements may be taken as capsules, tablets, chewable tablets, and liquids. The most common tablet size is 325 mg (ferrous sulfate). Other common chemical forms are ferrous gluconate and ferrous fumarate.

Have your health care provider tell you how many pills you should take each day and when you should take them. Taking more iron than your body needs can cause serious medical problems.

Blood counts return to normal after 2 months of iron therapy for most people. You may need to continue taking supplements for another 6 to 12 months to build up the body's iron stores in the bone marrow.

TIPS FOR TAKING IRON

Iron is best absorbed on an empty stomach. Yet, iron supplements can cause stomach cramps, nausea, and diarrhea in some people. You may need to take iron with a small amount of food to avoid this problem.

Milk, calcium and antacids should NOT be taken at the same time as iron supplements. You should wait at least 2 hours after having these foods before taking your iron supplements.

Foods that you should NOT eat at the same time as you take your iron include:

• High fiber foods, such as whole grains, raw vegetables, and bran
• Foods or drinks with caffeine

Some doctors suggest taking a vitamin C supplement or drinking orange juice with your iron pill. This can help the iron absorb into your body. Drinking 8 ounces (240 milliliters) of fluid with an iron pill is also OK.

Tell your provider about all the medicines you are taking.

• Iron tablets may cause other drugs you are taking to not work as well. Some of these include tetracycline, penicillin, and ciprofloxacin and drugs used for hypothyroidism, Parkinson disease, and seizures.
• Medicines that reduce stomach acid will impair iron absorption. Your provider may suggest changing these.
• Wait at least 2 hours between doses of these drugs and iron supplements.

SIDE EFFECTS

Constipation and diarrhea are very common. If constipation becomes a problem, take a stool softener such as docusate sodium (Colace).

Nausea and vomiting may occur with higher doses, but they can be controlled by taking the iron in smaller amounts. Ask your provider about switching to another form of iron rather than just stopping.

Black stools are normal when taking iron tablets. In fact, this is felt to be a sign that the tablets are working correctly. Talk to your provider right away if:

• The stools are tarry-looking as well as black
• If they have red streaks
• Cramps, sharp pains, or soreness in the stomach occur

Liquid forms of iron may stain your teeth.

• Try mixing the iron with water or other liquids (such as fruit juice or tomato juice) and drinking the medicine with a straw.
• Iron stains can be removed by brushing your teeth with baking soda or peroxide.

Keep tablets in a cool place. (Bathroom medicine cabinets may be too warm and humid, which may cause the pills to fall apart.)

Keep iron supplements out of the reach of children. If your child swallows an iron pill, contact a poison control center right away.

Brittenham GM. Disorders of iron homeostasis: iron deficiency and overload. In: Hoffman R, Benz EJ Jr, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 36.

Ginder GD. Microcytic and hypochromic anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 159.

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.