The 7 Best Iron Supplements, According to Dietitians

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If your iron levels are low, taking a supplement can help you combat fatigue, cold hands and feet and other symptoms tied to this deficiency.

Reviewed by Dietitian Brierley Horton, M.S., RD

Iron is an essential mineral that helps red blood cells carry oxygen throughout your entire body.  Despite how important it is, iron deficiency is one of the most common nutrient shortfalls, affecting more than a billion people worldwide. If left untreated, iron deficiency can lead to anemia, a condition characterized by chronic fatigue, weakness, and shortness of breath, among other symptoms. "Those who are higher risk for iron-deficiency anemia include menstruating females, endurance athletes, people on a vegetarian or vegan diet, and those on a low-calorie diet," says Jessie Anderson, RD, CSSD, LD, ACSM EP-C, Board-Certified Specialist in Sports Dietetics with Top Nutrition Coaching.

If you find that you're always cold, tired, or winded more easily during exercise, you might want to get a blood test to check your iron status. If your levels are indeed low, your doctor may likely recommend an iron supplement.

To recommend the best iron supplements on the market we researched the most common brands and spoke to dietitians. To help you get your iron levels back up to a healthy range, consider the picks below, and—remember—always check with your doctor before starting a supplement.

Our Iron Supplement Recommendations

• Best Overall: Pure Encapsulations OptiFerin-C

• Also Great: Thorne Iron Bisglycinate

• Best Value: Nature Made Iron

• Best for Anemia: Thorne Ferrasorb

• Best for Pregnancy: Needed

• Best Vegan: MegaFood Blood Builder
  

• Gentlest on the Stomach: GNC Gentlesorb Iron

Related: EatingWell’s Supplement Philosophy & Methodology

When should I consider taking iron supplements?

If your blood test results show your iron levels aren't up to par, your doctor will recommend a supplement—and only then should you take an iron supplement. Once you start taking iron pills, you'll likely notice some of your deficiency symptoms begin to improve. "Generally, the effects of iron supplementation become noticeable within one to three weeks of consistent use," says Kathleen Benson, RDN, CSSD, a dietitian with Top Nutrition Coaching. This can vary depending on individual health conditions and the severity of your iron deficiency, though.

If you haven't undergone lab tests to assess your need for iron supplementation, you should avoid iron supplements, Benson says. People living with hereditary hemochromatosis, hemosiderosis or those who have a history of hemolytic anemia should also avoid iron pills, Anderson says.

Best Overall: Pure Encapsulations OptiFerin-C

$21 at Amazon

$15 at Walmart

What we like: This supplement contains a highly absorbable form of iron plus vitamin C to further increase the iron's absorption; plus, it's third-party-tested and free of unnecessary additives.

What to know: One small pill delivers 156 percent of your daily value for iron.

Pure Encapsulations has a reputation for high-quality, third-party-tested products, and this iron supplement is no exception. Pure Encapsulations OptiFerin-C is formulated with iron bis-glycinate, a type of iron known for its easy digestibility. "This supplement also includes vitamin C for better absorption and a trace amount of calcium, which adds to its gentleness without significantly impacting iron absorption," says Benson.

You'll get 28 milligrams or 156 percent of your daily value (DV) for iron in one small pill. Pure Encapsulations crafts its capsules without unnecessary coatings, bindings, fillers or preservatives, and they're vegan and free of gluten, artificial flavors and colors and other allergens and ingredients. We also love that the brand tests its ingredients in independent labs and holds its ingredient suppliers to high testing and quality criteria to ensure their supplements' purity and potency.

Type: Iron bis-glycinate | Amount per serving: 28 mg (156% DV) | Third-party tested: Yes | Price: $21 | Form: Capsule

Also Great: Thorne Iron Bisglycinate

$13 at Amazon

$14 at Walmart

What we like: They're NSF-Certified for Sport and contain a highly absorbable form of iron that's associated with fewer side effects.

What to know: It doesn't contain vitamin C, which helps to maximize iron absorption.

Thorne's iron supplement is an excellent choice for those who prefer pure iron without additional ingredients. It's NSF Certified, which means this supplement has been tested for and is free of unsafe levels of contaminants and prohibited substances for athletes. "Renowned for its quality, Thorne offers a straightforward, high-quality iron solution," Benson says.

One capsule packs 25 milligrams (139% DV) of iron, helping to build up your blood, fight fatigue and banish other low-iron symptoms. Thorne's pills contain iron bis-glycinate, a form of iron that's easier on the digestive system, which is why Anderson recommends these. While this form of iron is easily absorbed by the body, it's worth noting that this supplement doesn't contain added vitamin C to further help with iron absorption.

Type: Iron bis-glycinate | Amount per serving: 25 mg (139% DV)  | Third-party tested: Yes | Price: $14 | Form: Capsule

Best Value: Nature Made Iron

$13 at Amazon

$7 at Target

What we like: These are very budget-friendly (you get a 6-month supply in a bottle) and contain a high dose of iron to help correct a deficiency.

What to know: They contain a form of iron that may cause gastro issues such as constipation.

Nature Made's iron supplement averages around 5 cents per capsule, making it an economical option for long-term use. Each tablet contains 65 mg of iron—which is a whopping 361 percent of your daily recommended value—so you can further stretch out each bottle by taking these a few times a week rather than daily. "The higher dose may lead to typical iron-related side effects like constipation, so consulting with your physician about an every-other-day regimen could be a practical solution," Benson says.

Just because these are very affordable, doesn't mean you're skimping out on quality. Nature Made's iron supplement is USP-verified, which means it only contains the ingredients listed on the label in the stated amounts, and it's free of unsafe levels of contaminants such as heavy metals, pesticides and microbes. The iron in this supplement is ferrous sulfate, a form that may cause gastrointestinal issues like nausea or constipation. Drinking plenty of water and focusing on fiber can help keep things moving along, but if you're dealing with persistent symptoms, check with your doctor about changing your dosing.

Type: Ferrous sulfate | Amount per serving: 65 mg (361% DV) | Third-party tested: Yes | Price: $18 | Form: Tablet

Best for Anemia: Thorne Ferrasorb

$24 at Amazon

$24 at Walmart

What we like: It contains multiple nutrients for an all-around comprehensive anemia supplement.

What to know: It offers a lower dose of iron than other supplements, so you may have to take up to three capsules daily (under the guidance of your doctor).

When it comes to addressing anemia effectively, a supplement prescribed by a healthcare provider is ideal because it'll be tailored to your needs. But "among over-the-counter options, Thorne's Ferrasorb stands out for its formulation designed for optimal absorption, making it a strong choice in general scenarios," Benson says. Thorne's Ferrasorb is made with bis-glycinate, a chelated form of iron that's highly absorbable, plus vitamin C to boost the iron’s absorption. That's not all—this comprehensive supplement also contains methylated folate (vitamin B9) and vitamin B12, a form that some people need to be able to actually use the B vitamins. Plus, being deficient in these B vitamins can cause anemia as well.

Each easy-to-take capsule packs 36 mg or 200 percent of your iron DV, helping to build your hemoglobin, correct anemia and bust symptoms like fatigue, lack of focus, brittle nails and cold hands and feet with continued use. Plus, Thorne's supplement is NSF-certified and free of unsafe contaminants. The instructions recommend taking one to three capsules daily but check with your doctor for specific recommendations on dosing to correct your anemia before starting a supplement.

Type: Iron bis-glycinate | Amount per serving: 36 mg (200% DV) | Third-party tested: Yes | Price: $24 | Form: Capsule

Best for Pregnancy: Needed

$20 at Amazon

What we like: It contains a lower dose of iron, which allows you to tailor the dosage to your specific pregnancy or prenatal needs.

What to know: If you're on a multivitamin, you'll have to take this iron pill separately as it can interact with other nutrients.

Benson recommends Needed's iron supplement because it's tailored for expectant mothers. "It features the same iron form as Thorne's Iron Bisglycinate but at a lower dose of 13.5 mg," Benson says. "This accounts for half the recommended daily intake during pregnancy, offering the flexibility to double up on the dosage with an additional capsule if necessary, especially if your dietary iron intake is limited due to pregnancy-related food aversions."

Needed offers a handy chart with recommendations for the optimal dosing based on the stage you're in—for example, take one capsule per day during preconception and your first trimester and two capsules per day during your second and third trimester—but always check with your doctor before starting a supplement, especially if you're pregnant or planning to get pregnant. What's more, Needed is third-party-tested and contains a form of iron that's bioavailable and easy on the stomach, which is particularly important if you're already dealing with GI issues during your pregnancy.

Just note that if you take a prenatal multivitamin, you'll have to take this iron supplement separately as iron can interact with other nutrients. For instance, calcium will inhibit iron’s absorption. You should take your iron two hours before or after other supplements and some medications.

Type: Iron bis-glycinate | Amount per serving: 13.5 mg (50% DV) | Third-party tested: Yes | Price: $20 | Form: Capsule

Best Vegan: MegaFood Blood Builder

$15 at Amazon

$15 at Target

What we like: It contains vitamin C for greater iron absorption as well as B vitamins for blood support.

What to know: It's not third-party-tested but the brand tests its supplements for herbicides and pesticides.

Supplements often contain animal-derived ingredients, such as gelatin, so if you're on a vegan diet, you'll have to be extra careful to pick a product that fits your needs. And also, vegans and vegetarians are at a greater risk for iron deficiency because the best food sources of iron are animal proteins.

MegaFood's Blood Builder is a great food-derived vegan supplement ​​that can support red blood cell formation and total-body health without GI-related side effects. "It not only includes a gentle form of iron but also enriches it with a blend of fruits and vegetables, vitamin C for enhanced absorption, and other blood-supportive ingredients like folate and B12," Benson says. The serving size is just one tablet per day, which includes 26 mg (or 144 percent DV) of iron bis-glycinate.

Type: Iron bis-glycinate | Amount per serving: 26 mg (144% DV) | Third-party tested: No (but tested in-house) | Price: $15 | Form: Tablet

Gentlest on the Stomach: GNC Gentlesorb Iron

$15 at Amazon

$15 at gnc.com

What we like: It contains a well-tolerated form of iron at a lower dose to minimize GI side effects.

What to know: It doesn't contain vitamin C for better iron absorption.

GNC Gentlesorb Iron, with its chelated iron formulation, is an excellent choice for those with sensitive stomachs, Benson says. "This type of iron is known for its quick absorption and reduced likelihood of causing gastrointestinal discomfort," she says, adding that the moderate dosage of 18 mg (100% DV) further aids in minimizing any potential stomach upset.

We like that you only have to take one capsule, and these are vegetarian and free of gluten, corn, dairy and artificial colors and sugars. GNC's iron supplement is tested by ConsumerLab, which confirms it contains the amount of iron listed on the label and is free of heavy metals. The only downside is that it’s another iron supplement that doesn't contain vitamin C for optimized iron absorption.

Type: Hydrolyzed protein chelate | Amount per serving: 18 mg (100% DV) | Third-party tested: Yes | Price: $15 | Form: Capsule

The Bottom Line: The Best Iron Supplement

Pure Encapsulations OptiFerin-C (view at Amazon) won the top spot on our list because it's third party-tested and formulated with a highly absorbable form of iron as well as contains vitamin C to maximize iron absorption. Thorne Iron Bisglycinate (view at Amazon) is another solid option because it's NSF-Certified for Sport and contains a highly absorbable form of iron that's less likely to cause GI issues.

Choosing an Iron Supplement

Select your preferred form

Iron supplements most commonly come in capsules, liquids, chewables or gummies, and each type has its pros and cons. Iron capsules offer precise dosing and are well-absorbed by the body but may cause side effects such as GI distress and constipation, Benson says.

Liquid iron supplements are also easily absorbed and not as hard on the gut but come with a higher risk of taking too much since the dosage can be more difficult to measure.

Gummies are easy to take, but most types contain extra ingredients (like added sugar and gelatin) and may require more servings to meet requirements for those with iron-deficiency anemia, Anderson says.

It's also important to consider the type of iron in your supplement. According to Benson, the most common types of supplemental iron include:

• Ferrous Fumarate: Boasts a high iron content but comes with potentially more side effects.

• Ferrous Sulfate: Widely available and cost-effective but may cause gastrointestinal side effects.

• Ferrous Gluconate: Gentler on the stomach but lower in iron content.

• Chelated Iron Forms (such as iron bis-glycinate and hydrolyzed protein chelate): Typically have fewer gastrointestinal side effects but may be more expensive or harder to find.

Look for third-party testing

Unlike medications, supplements aren't approved by the FDA before going to market, which is why we recommend choosing supplements that are third-party-tested as often as possible. Many organizations, such as USP, NSF, Informed Sport and other independent labs test supplements for quality, safety and potency. "Choosing supplements from reputable brands that adhere to quality standards and undergo third-party testing ensures the product's purity and efficacy," Benson says.

Read the ingredients

When shopping for an iron supplement, prioritize those that are primarily composed of iron or include iron combined with vitamin C for enhanced absorption, Benson says. "While supplements with a blend of herbs and other ingredients exist, simpler formulations are often more evidence-based and safer," she says.

You'll also want to be wary of unnecessary additives and fillers that may not contribute to the supplement's effectiveness or could cause adverse reactions. "Reading labels carefully and consulting with a healthcare provider is advisable, particularly for those with specific health concerns or dietary needs," Benson says.

Our Search for the Best Iron Supplements

We researched many different brands of iron supplements and interviewed two registered dietitians for the products they recommend and what to look for in a quality supplement. The products on our list are all recommended by dietitians and are either third-party-tested for purity and potency or tested in-house per rigorous standards.

Common Questions

What are the signs and symptoms of iron deficiency?

Iron-deficiency anemia is a condition characterized by low levels of iron in the blood. Without enough iron, your body can't produce enough hemoglobin, which allows red blood cells to shuttle oxygen throughout your body.

Symptoms of iron deficiency anemia include fatigue, weakness, change in mood or motivation and focus, headache, dizziness, shortness of breath, pale skin, cold hands and feet, brittle nails, fast heartbeat or chest pain, unusual cravings (like for ice or dirt), tongue soreness and poor recovery from exercise.

If you think you're low on iron, visit your doctor for a blood test to check your iron levels.  "Results of the lab work will determine the need and appropriate iron dosage," Anderson says.

How can I get enough iron from food?

Animal proteins, such as red meat, poultry, eggs, and seafood, are the best sources of iron because they contain heme iron, a type that's easily absorbed by the body. Some plant-based foods are also high in iron, including leafy greens, legumes, seeds and nuts. These vegan sources contain non-heme (plant-based) iron, which isn't as well-absorbed by the body, but you can increase their absorption by pairing them with vitamin C-rich foods (fruits and veggies).

When is the best time to take iron supplements?

The optimal time to take iron supplements is usually on an empty stomach, or at least 2 hours after a meal, to enhance absorption, Benson says.

You'll also want to avoid taking your supplement hours after a workout. Hepcidin is a peptide hormone that reduces iron absorption, and it peaks about 3 to 6 hours after exercise, Anderson says. So take iron supplements in the morning to avoid hepcidin and before or as close to the completion of exercise as possible.

But if you get gastrointestinal side effects, it may be helpful to reduce the dose or take the supplement closer to meal times. If you have iron deficiency, avoid consuming coffee, tea, dairy products and calcium supplements one hour before or two hours after taking iron supplements, as these can interfere with iron absorption, Benson says.

Consistency is key, so try to take your supplement at the same time each day, or follow the schedule recommended by your healthcare provider.

Do iron supplements cause constipation?

Iron supplements can cause constipation due to their osmotic effect—e.g., they draw water away from the lower gastrointestinal tract, which can result in harder stools, Benson says.

Taking iron supplements on an empty stomach is recommended, but doing so may increase your risk of getting constipation. If you find that your iron supplement is constipating you and causing GI distress, try taking it with a meal and increase your intake of fiber-rich foods (fruits, whole grains, nuts, veggies, legumes), drink plenty of water, and engage in regular physical activity, Anderson says.

You might also try switching to a different form of iron like iron bis-glycinate, which is associated with fewer gastrointestinal side effects and may help some people avoid constipation.

What are some of the other side effects of iron supplements?

Contact your doctor if you experience severe or persistent symptoms such as constipation, stomach pain, diarrhea, nausea or teeth staining, Benson says. If you're experiencing ongoing side effects, your doctor might switch you to a different supplement, have you take it closer to mealtime, or recommend you take the supplement a few times a week rather than daily.

Iron supplements usually contain more iron than the body can absorb. Because of this, a large amount of iron ends up sticking around in the intestinal tract, and some research shows that this can potentially lead to the production of free radicals and inflammation, Anderson says.

"It’s also important to highlight that accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6 years of age," Benson says. Always keep these supplements out of reach of children. In the event of an accidental overdose, immediately contact a healthcare professional or a poison control center. Ensuring the safe use and storage of iron supplements is crucial for health and safety, especially in households with young children.

Can I take iron supplements with other medications?

Iron supplements interact with many different types of medications, including nonsteroidal anti-inflammatory drugs (NSAIDs), allopurinol (Zyloprim), penicillamine, drugs that treat GERD and other stomach issues and antacids. Aim to take your iron pills at least 2 hours before or 2 hours after taking these medications.

"It's crucial to inform your healthcare provider about all prescription and non-prescription medications, vitamins, supplements, and herbal products you are currently using or planning to use, to avoid any potential adverse interactions," Benson says.

Our Trusted Expertise

April Benshosan has been reporting on nutrition, health, and expert-recommended products from the start of her journalism career. She interviewed two registered dietitians for their top picks and asked them what to look for in a quality supplement:

• Jessie Anderson, RD, CSSD, LD, ACSM EP-C: a board-certified specialist in Sports Dietetics with Top Nutrition Coaching

• Kathleen Benson, RDN, CSSD: also a dietitian with Top Nutrition Coaching

This article was reviewed and edited by Brierley Horton, M.S., RD, a senior commerce editor with over 15 years of experience writing about nutrition, health and food.

Read the original article on Eating Well.