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Thorne, Pure Encapsulations, and MegaFood top our list of best iron supplements. See what else we recommend and what to look for when choosing for yourself.
Your body depends on iron for vital processes, such as oxygen transportation, hormone production, growth, and neurological development.
Most people can get all the iron they need by eating a nutrient-dense, well-rounded diet. But if you have inadequate iron intake, increased need, or impaired absorption, you may be at risk of low iron levels and iron deficiency anemia.
If a healthcare professional recommends supplemental iron, you might consider the following options vetted by Healthline’s medical and nutrition experts.
A note on price
Prices for iron supplements range from $0.04–$0.86 per serving or $10.35–42.99 per container, though this may vary depending on where you shop.
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:
Form
Bioavailability
Affordability
Side effects
Iron bisglycinate chelate
highly absorbable
a bit more expensive than other forms of iron
minimal gastrointestinal side effects compared with ferrous sulfate
Ferrous sulfate
well absorbed
inexpensive
in high doses, may cause gastrointestinal side effects like constipation
Ferric sulfate
less bioavailable than iron bisglycinate chelate and ferrous sulfate
inexpensive
in high doses, may cause gastrointestinal side effects like constipation
Ferrous fumarate
well absorbed
inexpensive
in high doses, may cause gastrointestinal side effects like constipation
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:
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
Warning about iron and children
Health experts do not recommend giving an iron supplement to your child unless a healthcare professional directs you to do so. Children are more susceptible to iron toxicity than adults.
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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.
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.
It’s important to consider several factors when choosing an iron supplement, including the type of iron, provided dose, and product quality and safety.
Keep in mind that if you’re low on iron, you’ll need more iron than most other people need each day.
If you have low iron stores, have a deficiency, or need extra iron for any reason, a healthcare professional can recommend a dosage that fits your needs.
What is the most effective form of iron supplement?
Many forms of supplemental iron are effective for increasing iron levels.
Ferrous forms of iron tend to be more bioavailable than ferric iron, meaning your body more easily absorbs them.
However, some forms of iron, including ferrous sulfate, are more likely to cause gastrointestinal side effects like constipation than other forms, such as iron bisglycinate chelate.
So, iron bisglycinate chelate is a good overall option for raising iron levels that’s also gentle on the stomach.
Meanwhile, iron supplements come in several options, including liquids, capsules, and chewable products. Liquid and chewable iron supplements are a good choice if you cannot tolerate pills or capsules.
Some people, such as those with health conditions that cause nutrient malabsorption, may require iron infusions. These are administered and monitored by a healthcare team.
What is the best iron supplement for anemia?
If you have iron deficiency anemia, ferrous forms of iron, such as ferrous sulfate, tend to be more bioavailable than ferric iron.
Iron bisglycinate chelate is also effective for treating iron deficiency anemia. Plus, it’s gentle on the stomach. It’s often preferred over ferrous and ferric salts because it’s less likely to cause gastrointestinal side effects like constipation.
How much iron should I take?
The amount of iron you should take depends on your iron levels.
For people with iron deficiency, the typical recommendation is to take divided daily doses to reach 100–200 mg of elemental iron per day.
However, research suggests that taking smaller doses of iron once daily and taking iron every other day may help improve absorption and tolerability compared with taking large daily doses of iron.
What iron supplement is best for sensitive stomachs?
Many forms of iron are gentle on the stomach and less likely to cause gastrointestinal side effects.
If you need an iron supplement but are concerned about potential side effects like constipation, it’s best to choose a supplement that contains iron in the form of iron bisglycinate chelate over supplements that contain ferric or ferrous salts, such as ferrous sulfate.
Iron is an important mineral that’s necessary for oxygen transport and the formation of healthy red blood cells.
While it’s always best to fulfill your iron needs through a diet high in iron-rich whole foods, supplements may sometimes be necessary to help you reach your daily iron needs.
Many types of iron supplements are available and contain varying doses and forms of the mineral.
Consult a healthcare professional before taking any new supplement and consider the factors mentioned above to help you choose a high quality product.
Last medically reviewed on October 27, 2023
How we reviewed this article:
Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
Makinen KK. (2016). Gastrointestinal disturbances associated with the consumption of sugar alcohols with special consideration of xylitol: Scientific review and instructions for dentists and other health-care professionals. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5093271/