Iron is an essential mineral present in:

• Hemoglobin: This protein transports oxygen from your lungs to your tissues.
• Myoglobin: This is another protein that carries and stores oxygen for your muscles.

Iron is also essential for:

• brain cell development
• physical growth
• hormone synthesis
• muscle metabolism

To support these important processes, your body needs a steady supply of iron from your diet.

Iron exists in two forms in nature:

• Heme iron: This iron is found in animal-derived foods. The human body readily absorbs it.
• Non-heme iron: This form is found in plant-based and iron-fortified foods. The body doesn’t absorb it as well as it does heme iron.

You can also take iron supplements. Iron supplements may be necessary for people who don’t get enough iron in their diet and those with increased iron needs.

Types of iron

For people who need an iron supplement, choosing the right one can feel overwhelming. There are so many options, not to mention different forms and doses.

Supplemental iron comes in different forms, including:

• ferrous sulfate
• ferrous fumarate
• ferrous bisglycinate
• ferrous gluconate

While all these forms can effectively raise iron levels, some are a bit harder on your digestive system.

For example, ferrous sulfate is one of the most common forms of iron. But it’s more likely to cause gastrointestinal side effects like nausea and constipation.

Meanwhile, ferrous bisglycinate is highly absorbable and unlikely to cause side effects. Ferrous bisgycinate chelate is often considered one of the best tolerated iron supplements.

Additionally, iron supplements come in various doses, which can increase the risk of side effects.

Taking higher doses of iron — 45 mg or more per day — is more likely to cause more gastrointestinal side effects than lower doses.

Here’s a more in-depth overview of the types of iron you might find in popular supplements, including their bioavailability, affordability, and side effects:

Who should take iron supplements?

People with adequate iron stores should aim to meet their iron needs through foods rather than supplements. However, you might need an iron supplement if you:

• are treating an existing iron deficiency
• have low iron stores
• are trying to maintain healthy iron levels

People at risk of developing an iron deficiency who may benefit from an iron supplement include:

• infants and kids
• pregnant people
• people with heavy menstrual bleeding
• people with certain forms of cancer, such as colon cancer
• people with gastrointestinal disorders, such as celiac disease and Crohn’s disease
• people with heart failure
• people who frequently donate blood
• athletes

Some people with iron deficiency anemia may need iron infusions if:

• oral iron supplementation does not work
• their bodies can’t properly absorb iron
• their iron losses are too great to be treated with oral supplements

Overall, it’s wise to talk with a healthcare professional to find out whether an iron supplement is right for you.

How to take iron supplements

The typical treatment for iron deficiency anemia is taking daily oral iron supplements for at least 3 months to replenish iron stores.

Healthcare professionals may recommend some people continue to take iron supplements even after their hemoglobin levels return to normal.

For these people, taking an iron-only supplement is a good idea because other nutrients commonly found in multivitamins, such as calcium, may inhibit iron absorption.

Additionally, it’s recommended to take iron supplements between meals and avoid pairing them with foods or beverages that may inhibit iron absorption, such as:

• tea
• coffee
• milk

Instead, take iron with a source of vitamin C, such as orange juice or bell peppers. Vitamin C can help enhance iron absorption.

In terms of supplement forms, one of the best iron supplements for anemia that’s unlikely to cause constipation is ferrous bisglycinate chelate. It’s highly absorbable and gentle on the digestive system, making it a smart choice for those with sensitive stomachs.

Potential side effects and safety concerns

Certain iron supplements are more likely to cause side effects than others.

Potential side effects of taking iron supplements include:

• constipation
• diarrhea
• nausea
• abdominal pain

Iron can be toxic if taken in very high doses. To reduce the risk of side effects and toxicity, avoid exceeding the established tolerable upper intake levels for iron supplements unless a healthcare professional recommends it.

These levels are as follows:

• 40 mg per day for babies and kids
• 45 mg per day for teens and adults

Finally, it’s important to keep iron supplements out of reach of children because they are more susceptible to iron toxicity than adults.

Children may mistake iron supplements for candy and ingest large amounts, which can be fatal.

Drug interactions

Iron supplements may reduce the absorption of medications used to treat Parkinson’s disease.

Iron supplements may lower the effectiveness of levothyroxine, a common drug used to treat:

• hypothyroidism, also called an underactive thyroid
• goiter
• thyroid cancer

On the other hand, some medications — such as proton pump inhibitors, which treat acid reflux or stomach ulcers — can reduce iron absorption because they lower gastric acid secretion, which plays a key role in iron uptake.

When to contact a doctor

Having too little iron in your body can cause symptoms such as:

• fatigue
• weakness
• difficulty concentrating
• shortness of breath

Some people are more at risk of developing iron deficiency anemia, including:

• people with heavy periods
• pregnant people
• people with health conditions that cause nutrient malabsorption

If you think you may have an iron deficiency, visit a healthcare professional. They can check your iron levels with a blood test.

Do not try to treat an iron deficiency on your own. Even though most people respond well to oral iron supplements, some may need iron infusions to effectively increase their iron levels.