7 mins read

Iron supplements are taken to increase your iron levels. Common side effects include stomach pain or discomfort, nausea, constipation, diarrhea, or black poop. Accidental iron overdoses can lead to death, especially in children younger than 6 years old. Keep iron supplements out of the reach of children. Before taking an iron supplement, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

Uses

What are iron supplements used for?

Iron supplements are commonly taken to help with the following. 

These uses may vary depending on the specific iron supplement used. Iron supplements may also be taken for other conditions as determined by your health care provider.

How do iron supplements work (mechanism of action)?

Iron is a mineral. Your body uses it to make two proteins called hemoglobin and myoglobin. Hemoglobin helps in carrying oxygen from the lungs to all parts of your body. Myoglobin helps in getting oxygen to your muscles. Iron supplements work by increasing the iron levels in your body so that it can make hemoglobin and myoglobin to get oxygen where it is needed.

How are iron supplements supplied (dosage forms)?

Brands and other names

  • Fer-in-sol
  • Ferosul
  • Slow Fe

Iron supplements are available as a dietary supplement in various strengths and dosage forms. 

How should I store iron supplements?

Iron supplements should usually be stored at room temperature, between 68 F and 77 F (20 C and 25 C). They can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting them. Store in a cool, dry place. Follow the directions for your product or ask your pharmacist if you are not sure how to store your medicine.

Side Effects

What are the most common side effects of iron supplements?

The most common side effects of iron supplements are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Stomach pain or discomfort
  • Nausea or vomiting
  • Constipation
  • Diarrhea
  • Dark or black poop
  • Teeth staining (liquid iron supplements)

There may be other side effects of iron supplements that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of iron supplements?

While less common, the most serious side effects of iron supplements are described below, along with what to do if they happen.

Severe Allergic Reactions. Iron supplements may cause allergic reactions, which can be serious. Stop taking iron supplements and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use iron supplements?

Allergies to Ingredients. People who are allergic to any of the following should not take iron supplements.

  • Carbonyl iron
  • Fer-in-sol
  • Ferosul
  • Ferrous fumarate
  • Ferrous gluconate
  • Ferrous sulfate
  • Iron polysaccharide
  • Slow Fe
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the iron supplement products they stock.

High Iron Levels. If you have a condition where your body has too much iron, you should not take iron supplements. Examples of these conditions include hemochromatosis or hemolytic anemia. Tell your health care provider if you have either of these. 

What should I know about iron supplements before using one?

There are multiple forms of iron supplements available. Follow the instructions from your health care provider or those that come with the product. Do not take more than the recommended amount. If you have any questions, talk to your health care provider. 

Accidental iron overdoses can lead to death, especially in children younger than 6 years old. Keep iron supplements out of the reach of children.

Iron supplements come in a variety of iron salts. Each salt has a different percentage of actual iron in it, so not all iron supplements are the same. If you need to switch from one iron supplement to another, talk to your pharmacist or another health care provider about which one may be best and how much you should take. 

Iron supplements may commonly cause dark or black poop as a side effect. Talk to your health care provider if you have concerns.

If you are taking iron supplement tablets, do not chew, crush, or break them. You should swallow them whole. 

Some liquid iron supplements may be mixed with water or juice to reduce the chance of staining your teeth. They should not be mixed with milk or drinks fortified with calcium. Calcium may affect how well your body absorbs iron.

Use an accurate measuring device to measure your dose of liquid iron supplements. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist if you have questions or are not sure which measuring device to use.

Some liquid iron supplements need to be shaken well prior to measuring each dose. Follow the instructions on the package labeling. If you are not sure if you should shake an iron supplement, ask your pharmacist. 

What should I tell my health care provider before using iron supplements?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if an iron supplement is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have or have had any of the following.

Other Medicines and Supplements. Iron supplements may interact with other medicines and supplements. Before taking iron supplements, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take iron supplements while you are pregnant or trying to get pregnant.

Breastfeeding. Iron supplements pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take iron supplements while breastfeeding.

Interactions

Do iron supplements interact with foods or drinks?

Taking iron supplements with food can decrease the amount of iron your body absorbs. For best absorption, you should take iron supplements one hour before or two hours after eating. 

If iron supplements upset your stomach or cause nausea, then it may be helpful to take them with a small amount of food. If you do take them with food, avoid foods and drinks that are high in fiber or contain calcium (such as milk) or caffeine (such as coffee or tea). 

It is unknown if drinking alcohol will affect iron supplements, but both iron supplements and alcohol can upset your stomach.

Do iron supplements interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking iron supplements.

  • A tetracycline, such as doxycycline, minocycline, omadacycline (Nuzyra), sarecycline (Seysara), or tetracycline, which is a medicine used to treat infections or other conditions
  • A fluoroquinolone, such as ciprofloxacin (Cipro, Cipro XR, others), levofloxacin (Levaquin), moxifloxacin (Avelox), or ofloxacin (Floxin), which is a medicine used to treat certain infections
  • Levodopa, which is a medicine for Parkinson’s disease
  • A thyroid medicine, such as levothyroxine, which is used to raise thyroid hormone levels 
  • A proton pump inhibitor (PPI), such as esomeprazole (Nexium), lansoprazole (Prevacid), omeprazole (Prilosec), pantoprazole (Protonix), or rabeprazole (Aciphex)
  • An antacid, supplement, or laxative containing calcium
  • A bisphosphonate, such as alendronate (Binosto, Fosamax), ibandronate, or risedronate (Actonel, Atelvia), which is a medicine commonly used for osteoporosis

Iron supplements may affect the absorption of some other medicines. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with iron supplements. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much of an iron supplement?

If you or someone else has taken too much of an iron supplement, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of an iron supplement?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.