Iron Pills: Side Effects and Benefits of Supplements

Iron supplements, also known as iron pills, are commonly used to treat or prevent iron deficiency anemia. While beneficial in relieving iron deficiency, iron pills can cause side effects like constipation, diarrhea, nausea, vomiting, dark stools, stomach cramps, and a metallic taste. Iron overload (a.k.a. "iron poisoning") is possible if taken in excess.

Iron pills are available over the counter and by prescription as capsules, tablets, chewables, gummies, and liquid solutions. Your healthcare provider can help you decide which iron supplement is best for you.

This article explains when iron supplements are used and how to use them safely. It also describes iron pill side effects and ways to avoid them.

Symptoms of Iron Deficiency

Iron is one of the minerals your body needs to function normally. The body uses iron to make hemoglobin, the molecule in red blood cells that "carries" oxygen to cells. When you don't have enough iron, you can develop a type of anemia known as iron deficiency anemia.

Symptoms of iron deficiency include:

• Persistent fatigue
• Weakness
• Headaches
• Dizziness
• Heart palpitations (skipped beats)
• Problems concentrating or thinking

If allowed to persist, iron deficiency can lead to more concerning symptoms like:

• Lightheadedness when standing
• Mouth ulcers
• Sore tongue
• Shortness of breath
• Pallor (pale skin color)
• Brittle nails
• Restless leg syndrome (uncontrollable leg movements)
• A bluish color to the whites of your eye
• Hair loss
• Pica (the desire to eat non-food things)
• Orthostatic hypotension (feeling lightheaded when you stand up)

Who Is at Risk for Iron Deficiency? 

Iron is an important mineral that you can only get from food. Iron deficiency occurs when the iron stores in your body run below what is needed to function normally.

The four main reasons for low blood iron include:

• You lose more blood faster than your body can replace.
• Your body is unable to properly absorb iron from food (called iron malabsorption).
• You are not eating enough iron-rich foods.
• You have a greater-than-normal need for iron (such as being pregnant or breastfeeding).

People at Risk of Iron Deficiency

There are groups of people who are vulnerable to iron deficiency for different reasons.

Iron deficiency due to blood loss can affect people with:

• Heavy, long, or frequent menstrual periods
• Peptic ulcer (stomach ulcers)
• Gastrointestinal bleeding from the overuse of nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin, Advil (ibuprofen), or Aleve (naproxen)
• Cancer of the esophagus (windpipe), stomach, or colon
• Liver cirrhosis (which can cause esophageal bleeding)

Iron deficiency due to iron malabsorption can be caused by:

• Celiac disease
• Crohn disease
• Ulcerative colitis
• Gastric bypass surgery
• Excessive antacid use

Iron deficiency due to diet can affect those with:

• A strictly vegan or vegetarian diet
• Malnutrition

Childhood and Pregnancy

Children and pregnant people are especially vulnerable to iron deficiency for different reasons:

• Preterm babies: Infants born prematurely are often deficient because they have lower iron stores than full-term babies. Most iron is transferred from mother to child during the third trimester.
• Toddlers: Children under 2 years can become iron deficient if they drink too much cow's milk (more than 24 ounces per day) and/or do not eat enough iron-rich foods like leafy vegetables and red meat. Their smaller body size puts them at risk.
• Pregnancy: During pregnancy, the volume of blood in the body increases, along with the amount of iron needed to function normally. Unless you supplement your normal, iron deficiency can occur.
• Breastfeeding: During lactation, mothers are susceptible to anemia because of iron depletion and blood loss during childbirth.
  

Benefits of Iron Pills

Iron pills are used to treat 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 amount of iron you need each day depends on your age, sex, and pregnancy status. If you eat a healthy, balanced diet, you probably get enough iron from your food. Supplements can be used if you are not getting enough.

The National Institutes of Health (NIH) recommends the following daily intake of iron from all sources for the following groups:

• Birth to 6 months: 0.27 mg
• Children ages 7–12 months: 11 mg
• Children ages 1–3 years: 7 mg
• Children ages 4–8 years: 10 mg
• Children ages 9–13 years: 8 mg
• Males 14–18 years: 11 mg
• Females 14–18 years: 15 mg
• Males 19–50 years: 8 mg
• Females 19–50 years: 18 mg
• Adults 51 years and older: 8 mg
• Pregnant teens: 27 mg
• Pregnant adults: 27 mg
• Breastfeeding teens: 10 mg
• Breastfeeding adults: 9 mg
  

Iron Pills Side Effects

As with any supplement or medication you take, side effects can occur with iron pills. Most tend to be mild but can become severe if you overuse them.

Common Side Effects

Iron supplements are generally safe and well-tolerated if taken at the recommended dose. The most common side effects include:

• Upset stomach
• Dark or black stools
• Bloating
• Constipation
• Diarrhea
• Gas
• Nausea
• Stomach cramps
• Vomiting
• Metallic taste
• Teeth staining (when using a liquid iron supplement)

Less Common Side Effects

Other potential side effects of iron supplements include:

• Backache
• Chest pain 
• Chills
• Dizziness
• Fainting
• Flushing or red skin
• Groin pain
• Headache
  
• Muscle soreness
• Numbness, pain, or tingling of hands or feet
• An overall feeling of weakness
• Rapid heart rate
• Double vision

Rare Side Effects

In rare cases, a serious allergic reaction known as anaphylaxis can occur when taking iron supplements. Seek immediate emergency care if you experience the following signs and symptoms:

• Sudden hives or ash
• 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
• Wheezing
• A feeling of impending doom

Managing Side Effects

Iron supplement side effects can make it difficult for people to take them as prescribed. It often helps to start taking them with a lower dose and gradually increase the dose as tolerated.

There are several other tips and tricks that can help:

• Take iron pills with food to avoid gastrointestinal side effects.
• Drink plenty of water to prevent constipation.
• Eat more vegetables and fiber-rich foods to prevent or treat constipation.
• Eat soluble fiber-rich foods like bananas and sweet potatoes if you have diarrhea.
• Mix liquid iron with water or juice and drink it through a straw to avoid teeth staining.
• Brush your teeth and rinse thoroughly after drinking a liquid iron supplement.
  
• Sip ginger tea or suck on a ginger candy if you have nausea.

Iron Poisoning

Taking too much iron can lead to iron overload, also known as iron poisoning. Unlike some minerals, iron is not easily excreted from the body. Once the body's iron stores are full, it can accumulate in the liver, heart, joints, and pancreas and cause organ damage. Heart failure, liver cirrhosis, and hypothyroidism are just some of the possible complications.

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.

Signs of iron poisoning include:

• Joint pain
• Abdominal pain
• Loss of sex drive
• Erectile dysfunction
• Pale, clammy skin
• Unusual tiredness or weakness
• Depression
  

Late symptoms of iron overdose include:

• Bluish-colored lips, fingernails, and palms of hands
• Gray or bronze discoloration of the skin
• Weak, rapid heartbeats
• Shallow, rapid breathing
• Convulsions and seizures

Contact your healthcare provider immediately if you have iron poisoning symptoms.

Dosage and Preparation

Iron supplements are taken by mouth and formulated with one of several different types of iron known as:

• Ferrous sulfate (the most common type)
• Ferrous gluconate
• Ferrous fumarate
• Ferric citrate
• Ferric sulfate

Most iron pills sold in drugstores contain anywhere from 18 to 65 mg of iron. Depending on how much you take, you may meet or exceed the daily value (DV) recommended by the NIH.

According to the Office of Dietary Supplements:

• Multivitamin supplements with iron for women typically provide 18 mg of iron (100% of DV).
• Multivitamin supplements for men or seniors frequently contain less or no iron.
• Iron-only supplements usually deliver 65 mg of iron (360% of the DV).

While iron is best absorbed on an empty stomach, you should eat a small amount of food to avoid stomach upset. Drink a full 8-ounce glass of water or orange juice with each dose. The vitamin C in orange juice is said to boost absorption.

Vegetarians typically need twice as much iron as people who eat meat as the body doesn't absorb iron from plants (non-heme iron) as well as iron from animal-based foods (heme iron).

Interactions

Calcium and antacids can block the absorption of iron and should not be taken at the same time as an iron supplement. This includes taking an iron supplement with cow's milk. If you use antacids or calcium supplements, avoid taking them two hours before or after an iron supplement dose.

Iron supplements may also interact with the following drugs:

• Antibiotics like tetracycline, penicillin, and ciprofloxacin
• Levodopa used to treat Parkinson's disease
• Proton pump inhibitors used to treat acid reflux
• Synthroid (levothyroxine) used to treat thyroid disease
• Zinc supplements used to treat zinc deficiency

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 take iron supplements with these or any other chronic medication.

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 direct sunlight. 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.

Summary

Available over the counter and by prescription, iron supplements are mainly used to treat or prevent iron deficiency anemia. Side effects include dark stools, stomach cramps, nausea, diarrhea, constipation, and metallic taste. The dose varies by a person's age, sex, and pregnancy status as well as the cause and severity of the deficiency.