Should I take heme or non-heme iron for better absorption?

December 24, 2025 •

3 min read

Iron deficiency remains the most common nutritional deficiency worldwide, affecting over 2 billion people. For those seeking to boost their iron levels through diet or supplements, a critical question is whether they should take heme or non-heme iron. The optimal choice depends largely on absorption rates, dietary considerations, and your body’s unique needs.

Quick Summary

Heme iron from animal products is more readily absorbed by the body than non-heme iron from plants and supplements. The best option depends on dietary choices, absorption inhibitors, and individual needs, as non-heme absorption can be maximized with the right food pairings.

Key Points

Bioavailability Varies: Heme iron from animal products is absorbed much more efficiently by the body (15-35%) than non-heme iron from plants and supplements (2-20%).
Absorption Can Be Controlled: Non-heme iron absorption is enhanced by pairing with vitamin C but inhibited by compounds in coffee, tea, and dairy.
Heme is a Fast-Track: Heme iron is often recommended for individuals with severe iron deficiency or anemia due to its high and predictable absorption rate.
Non-Heme is Necessary for Plant-Based Diets: Vegetarians and vegans must rely on non-heme iron from plant sources and fortified foods, requiring careful planning to maximize intake and absorption.
Side Effects Differ: Heme iron supplements generally cause fewer gastrointestinal side effects than common non-heme iron supplements like ferrous sulfate, which can improve compliance.

Understanding the Two Types of Iron

Dietary iron comes in two fundamental forms: heme and non-heme iron. Heme iron is found exclusively in animal flesh, such as meat, poultry, and seafood, while non-heme iron is present in plant-based foods, fortified products, and also in animal flesh. The body absorbs and processes these types differently.

The Superiority of Heme Iron Absorption

Heme iron is absorbed as an intact molecule, leading to efficient absorption that is less affected by other dietary components. Absorption rates for heme iron can range from 15% to 35%, making it effective for increasing iron levels quickly. Heme iron supplements may also cause fewer gastrointestinal issues compared to some non-heme supplements. The presence of heme iron in a meal can even enhance the absorption of non-heme iron from other foods.

The Complexity of Non-Heme Iron Absorption

Non-heme iron absorption is more variable (2% to 20%) and depends heavily on meal composition. It needs to be converted before the body can absorb it. Consuming non-heme iron with vitamin C sources, such as citrus fruits or bell peppers, can significantly boost absorption. However, certain substances can hinder non-heme iron absorption, including phytates in grains and legumes, polyphenols in coffee and tea, and calcium from dairy and supplements.

Who Should Take Which Type?

Heme Iron is a strong consideration for:

Individuals with severe iron deficiency anemia needing rapid level increases.
Those experiencing gastrointestinal discomfort with other iron supplements.
People who consume and tolerate animal products.

Non-Heme Iron is the primary choice for:

Vegetarians and vegans, as it's the main form in plant foods.
Individuals with adequate iron stores, as the body can better regulate its absorption.
People with health concerns related to high red meat consumption.

Making Your Decision: Heme vs. Non-Heme Supplements

Most common iron supplements contain non-heme iron. While effective, they can cause side effects like constipation. Heme iron polypeptide supplements are available but may be more costly and less standardized. Consider your tolerance and diet when choosing a supplement.


Feature	Heme Iron	Non-Heme Iron
Primary Sources	Meat, poultry, seafood	Plant foods, fortified products, supplements
Bioavailability	High (15-35%)	Low and variable (2-20%)
Absorption Factors	Minimally affected by other foods	Enhanced by vitamin C; inhibited by phytates, polyphenols, and calcium
Best For	Quickly restoring iron levels, individuals with significant deficiency	Vegetarians, vegans, or those with less severe deficiency managed through diet
Potential GI Issues	Less likely to cause side effects	More likely to cause constipation and nausea
Cost	Generally more expensive in supplement form	More affordable and widely available in supplements

Heme and Non-Heme Food Sources

Heme Iron Sources:

Red meat (beef, lamb, organ meats like liver)
Seafood (oysters, clams, mussels, sardines, tuna)
Poultry (chicken, turkey)

Non-Heme Iron Sources:

Legumes: Lentils, beans, chickpeas
Nuts and Seeds: Pumpkin seeds, cashews
Dark Leafy Greens: Spinach, kale
Grains: Fortified breakfast cereals, oats, enriched rice
Dried Fruits: Apricots, raisins

Maximizing Non-Heme Absorption

To maximize non-heme iron absorption, combine non-heme sources with foods rich in vitamin C. Also, try to avoid consuming non-heme iron alongside inhibitors like coffee, tea, and calcium supplements. Consuming small amounts of heme iron with non-heme sources can also help.

Conclusion

Choosing between heme and non-heme iron depends on individual needs, dietary habits, and iron status. Heme iron is highly absorbable and has fewer side effects, beneficial for those with severe deficiencies who consume animal products. Non-heme iron, though less readily absorbed, is crucial for vegetarians and vegans and can be effectively managed with dietary strategies. Always consult a healthcare provider to determine the best approach for your specific situation. For detailed information on iron supplements, refer to the NIH Office of Dietary Supplements fact sheet.

Frequently Asked Questions

Heme iron, found in animal products, is significantly better absorbed by the body than non-heme iron, which comes from plants, fortified foods, and most supplements. The absorption rate for heme iron is much higher and less affected by other dietary factors.

Yes, it is possible to get enough iron from a plant-based diet, but it requires careful meal planning. Because the non-heme iron from plants is less bioavailable, strategies like pairing iron-rich foods with vitamin C are essential for maximizing absorption.

To increase non-heme iron absorption, pair iron-rich plant foods with sources of vitamin C, such as citrus fruits, bell peppers, tomatoes, and leafy greens. Also, eating meat, fish, or poultry (heme iron) with non-heme sources can improve absorption.

To avoid inhibiting non-heme iron absorption, it is best to avoid consuming coffee, tea, large amounts of milk, and calcium supplements with your iron-rich meals. For best results, consume these items a few hours before or after.

Most conventional over-the-counter iron supplements contain non-heme iron in various forms (e.g., ferrous sulfate, ferrous fumarate). Heme iron polypeptide supplements are also available but are less common and typically more expensive.

Heme iron is generally associated with fewer gastrointestinal side effects, such as constipation and nausea, compared to common non-heme iron supplements like ferrous sulfate. This is often due to its more efficient absorption pathway.

Pregnant women have a higher iron requirement and should discuss their needs with a healthcare provider. While both forms can be beneficial, many standard prenatal vitamins contain non-heme iron. In some cases, a doctor might recommend heme iron or a specific supplement based on the severity of any iron deficiency.