Iron Supplements: Side Effects, Uses, and More

Iron supplements, also known as “iron pills,” are commonly used to prevent and treat anemia. Anemia is a condition characterized by the lack of healthy red blood cells or hemoglobin.

Women of childbearing age, premature infants, young children, and people with chronic conditions are at greater risk of anemia.

Iron supplements are sold over-the-counter or by prescription. Common iron supplement side effects include constipation, diarrhea, dark stools, and a metallic taste in your mouth.

This article discusses iron supplements and how to use them. It also details iron supplement side effects and how to manage constipation and stomach upset from taking iron pills.

What Is Iron?

Iron plays a key role in making red blood cells that transport oxygen molecules throughout the body. Iron is also needed to metabolize the nutrients we eat and convert them into energy. Moreover, it contributes to the transmission of nerve signals to and from the brain.

While you will generally get enough iron from the foods you eat, there may be times when you may experience an iron deficiency. This commonly occurs during pregnancy or heavy menstruation.

Certain age groups and chronic illnesses can increase your iron deficiency risk. These include:

  • Celiac disease
  • Chronic heart failure
  • Preterm infants
  • Teenage girls
  • Ulcerative colitis
  • Young children

Iron supplements are also commonly prescribed to women of childbearing age to help prevent anemia.

Health Benefits

Iron supplements are used to treat iron deficiency and iron deficiency anemia. They are not typically used to treat other types of anemia (such as vitamin-deficiency anemia, hemolytic anemia, aplastic anemia, or anemia of chronic disease) unless iron deficiency is diagnosed. The response to oral iron supplements can vary by the underlying cause.

Iron Deficiency

Iron deficiency, also known as sideropenia, is the state in which your body lacks the iron needed to maintain normal function. Iron deficiency is common in the developing world, where more than a quarter of the population may be affected (mostly due to poverty and the lack of nutrition). While this is less common in the United States, it still does occur.

Iron deficiency can also occur due to physiological changes that leave you at a deficit. Iron deficiency can occur in children, for example, because their bodies grow so quickly. Starting in adolescence, a woman's iron need will increase due to her monthly menstrual cycle.

Whatever the cause, iron deficiency can lead to iron-deficiency anemia if left untreated. Iron supplements may not only be used to treat a deficiency but to prevent it from occurring in the first place.

Doing so can help prevent or treat many of the common symptoms of iron deficiency, including:

  • Fatigue
  • Weakness
  • Dizziness
  • Rapid heartbeat
  • Pale skin
  • Hair loss
  • Brittle or grooved nails
  • Sores at the corner of the mouth
  • Sore tongue
  • Twitches
  • Irritability
  • Frequent infections
  • Restless leg syndrome

Iron-Deficiency Anemia

When used to treat iron-deficiency anemia, iron supplements are sometimes effective and well-tolerated and, in other cases not.

Generally speaking, women with postpartum anemia respond best. Those with heavy menstrual bleeding or individuals with gastrointestinal-induced anemia tend to be moderate responders. All other cases are largely hit or miss in their response.

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If iron supplements are unable to provide relief, intravenous (IV) iron therapy or a blood transfusion may be needed.

Verywell / JR Bee

Iron Supplement Side Effects

Iron supplements are generally safe and well-tolerated if taken at the recommended dose. The most common iron supplement side effect is an upset stomach. This includes:

  • Black, green, or dark stools
  • Bloating
  • Constipation
  • Diarrhea
  • Gas
  • Nausea
  • Stomach cramps
  • Vomiting

Other potential side effects of iron supplements include:

  • Backache
  • Chest pain 
  • Chills
  • Cramps
  • Dizziness
  • Fainting
  • Flushing or red skin
  • Groin pain
  • Headache
  • Hives
  • Metallic taste
  • Muscle soreness
  • Numbness, pain, or tingling of hands or feet
  • Overall feeling of weakness
  • Rapid heart rate
  • Skin rash
  • Teeth staining (from liquid iron)

In rare cases, a serious allergic reaction to iron supplements can occur. Seek immediate medical care if you experience a possible anaphylactic reaction to iron. Warning signs of anaphylaxis include:

  • Hives
  • Itching
  • Rash
  • Red, swollen, blistered, or peeling skin 
  • Swelling of the mouth, face, lips, tongue, or throat
  • Tightness in the chest or throat
  • Trouble breathing, swallowing, or talking
  • Unusual hoarseness
  • Wheezing

Gastric bleeding can also occur while taking iron supplements. Call your doctor if you have any of the following: 

  • Black tar-like or bloody stools
  • Fever
  • Vomiting blood or what looks like coffee grounds

Managing Side Effects of Iron Supplements

Side effects from iron supplements can make it difficult for some people to comply with treatment. Avoid taking iron pills on an empty stomach, which increases the risk of gastrointestinal side effects. To reduce the risk of side effects, start with a lower dose and gradually increase the dose as tolerated.

Try the following tips to prevent and manage stomach upset while taking iron supplements:

  • Drink plenty of water to prevent constipation
  • Eat more vegetables and fiber-rich foods to prevent or treat constipation
  • Take a stool softener to treat constipation
  • Take with food to minimize or prevent stomach discomfort

Iron Overload

Taking too much iron can lead to iron overload. Extra iron in your blood can be toxic to the liver, heart, and pancreas and may cause damage to the joints, as well.

Excessive doses of iron can lead to iron poisoning. Even a single high dose (60 milligrams per kilogram of body weight or more) can lead to death. Iron poisoning symptoms usually become apparent within six to 24 hours of a dose.

Signs of iron poisoning include:

  • Abdominal pain
  • Bloody vomit or stools
  • Excessive diarrhea
  • Severe vomiting

Contact your healthcare provider if you have iron overload or iron poisoning symptoms.

Drug Interactions

Taking iron supplements containing 25 milligrams or more of elemental iron can affect the absorption of zinc and lead to a zinc deficiency. (Elemental iron is not the same thing as the iron supplement dose. Check the product label or speak with your pharmacist who can show you the difference.)

Iron supplements may also interact with the following drugs:

  • Levodopa used to treat Parkinson’s disease
  • Proton pump inhibitors, including Prevacid (lansoprazole) and Prilosec (omeprazole)
  • Synthroid (levothyroxine) used to treat thyroid disease

In some cases, separating the doses by two hours may be all that is needed to avoid interactions. In other cases, a dose adjustment may be needed. Speak with your healthcare provider if you intend to use iron supplements and take these or any other chronic medication.

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Dosage and Preparation

Iron supplements come in three main forms. Ferrous sulfate is the most common. Other chemical compounds include ferrous gluconate and ferrous fumarate. Iron supplements are sold as tablets, capsules, and liquid.

The dose can vary based on the level of your deficiency as well as the underlying cause. Your healthcare provider will recommend a dose based largely on the Recommended Dietary Allowance (RDA) for iron for your age, sex, and pregnancy status, as follows:

  • Birth to six months: 0.27 mg
  • Seven to 12 months: 11 mg
  • One to three years: 7 mg
  • Four to eight years: 10 mg
  • Nine to 14 years: 8 mg
  • Boys 14 to 18 years: 11 mg
  • Girls 14 to 18: 15 mg
  • Men 19 to 50: 8 mg
  • Women 19 to 50: 18 mg
  • Pregnant women 14 to 18: 27 mg
  • Breastfeeding women 14 to 18: 10 mg
  • Pregnant women 19 to 50: 27 mg
  • Breastfeeding women 19 to 50: 9 mg

Drink a full glass of water or orange juice with each dose. The vitamin C in orange juice is said to boost absorption. The water helps disperse the iron for better absorption.

When used to treat iron-deficiency anemia, the duration of therapy may be as long as six months. This requires a commitment on your part. Once started, you would need to continue treatment even if you feel better and no longer have symptoms.

What to Look For

Vitamin and mineral supplements are not subject to rigorous testing in the United States and can vary from one brand to the next.

To ensure quality and safety, opt for supplements that have been tested and approved by an independent certifying body like the U.S. Pharmacopeia (USP), ConsumerLab, or NSF International.

Iron supplements can degrade when exposed to excessive temperatures and UV radiation. To avoid this, keep the supplements in their original light-resistance container and store them in a dry, cool room. Always check the use-by date and discard any expired, discolored, or damaged supplements.

— Update: 30-12-2022 — found an additional article Too many iron supplements can poison you — here's how much you should take from the website for the keyword feroglobin side effects.

  • Iron supplements can cause side effects like dizziness, fainting, and hives. 
  • Too many iron supplements can cause long-term side effects like liver damage and heart disease.
  • If you want to take iron supplements, talk to your doctor about finding the proper dosage for you. 

When a person isn’t getting enough iron, they may experience symptoms such as excessive fatigue, shortness of breath, and anemia.

Taking iron supplements may help alleviate these problems but can also come with its own potential side effects when iron is taken in high doses and in excess of your needs.

Medical term: Iron is an essential mineral that helps your body create red blood cells, and is found in foods, such as dark chocolate, spinach, and beef. 

Here’s what you need to know about taking iron supplements and how to lower your risk of unpleasant side effects.

Iron supplement side effects   

Iron supplements can contain more than 100% of your daily iron needs, which means it can be easy to exceed your upper limit for iron and experience side effects as a result.

General advice: The upper limit for iron is 40 mg for people 13 years or younger and 45 mg for people 14 years or older. 

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Ingesting too much iron can corrode tissue in the gastrointestinal tract. “Over time, iron can accumulate in the organs, and cause irreversible damage to organs like the liver and brain,” says DeMasi.  

Initial side effects of iron supplements

  • Chills
  • Gastrointestinal distress
  • Dizziness
  • Fainting
  • Hives
  • Tingling sensation in the feet or hands

Although rare, if you consume too much iron over time it can cause iron toxicity, which can lead to:

  • Liver disease
  • Brittle bones
  • Heart disease 

Visit a doctor immediately if you or children in your care experience any side effects from iron supplements. 

An iron overdose can be deadly for children. Between 1983 and 2000, 43 children died after ingesting high doses of iron. 

“Iron toxicity is extremely dangerous for children and can lead to multi-organ failure or death in severe cases,” says DeMasi. “The first signs of toxicity are nausea, vomiting, diarrhea, and stomach pain.” 

Iron supplement dosage 

Before taking an iron supplement, speak with a doctor to determine the proper dosage. Overall, the amount of iron a person should take per day depends on their age and gender:

  • Children 1 to 3 years: 7 mg
  • Children 4 to 8 years: 10 mg 
  • Children 9 to 13: 8 mg 
  • Adolescent males: 11 mg
  • Adolescent females: 15 mg 
  • Adult males: 8 mg 
  • Adult females: 18 mg 
  • Pregnant people: 27 mg

According to DeMasi, people who are at a high-risk of iron overdose, and therefore, should not supplement, include those with:

Most other individuals do not need to take iron supplements. “Individuals who have normal iron and hemoglobin levels and are not pregnant and of child-bearing age do not generally need iron supplements,” says Bansari Acharya, a registered dietitian-nutritionist. 

General advice: If you think you may have an iron deficiency or are considering taking iron supplements, reach out to your doctor. They can run a hemoglobin test to diagnose you and help you find the proper dosage.

Iron supplements are available in many forms, including: 

  • Powder
  • Chewable tablet 
  • Capsule
  • Extended-release 
  • Liquid
  • Syrup

Tips for taking iron supplements

The body does not absorb iron as well if it’s coming from supplements. However, there are a few ways you can improve your body’s ability to absorb iron. According to DeMasi and Acharya, these include: 

  • Eat more vitamin C-rich foods like citrus fruits, strawberries, bell peppers, and broccoli.
  • Avoid consuming food or beverages high in calcium, like milk or yogurt when you take supplements, as they can limit iron absorption. 
  • Take iron supplements one hour before a meal or two hours after since it’s best absorbed on an empty stomach. 

The form of iron supplements you take can also help mitigate side effects. According to DeMasi, some people find liquid iron and slow-release iron cause fewer gastrointestinal side effects, since they are more readily absorbed.

Insider’s takeaway

Iron supplements can lead to side effects such as gastrointestinal distress and fainting. If you continue to supplement with much more iron than you need, you may experience iron toxicity, which can lead to brittle bones or liver disease.

Unless you are in a high-risk group or have low iron levels, iron supplementation is usually unnecessary. 

If you are considering taking iron supplements, speak with your doctor first as they can help you determine the correct dosage. 


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