What kind of fish has the most iron in it?

December 25, 2025 •

4 min read

Shellfish, particularly clams and oysters, stand out as an exceptional source of heme iron, a form that the body absorbs more efficiently than plant-based iron. Knowing which seafood is richest in this vital mineral is essential for anyone looking to boost their intake through diet.

Quick Summary

Clams and oysters contain the highest iron content among seafood, providing an easily absorbed form of the mineral. Other notable options include sardines, anchovies, and mackerel.

Key Points

Clams and Oysters: Shellfish like clams and oysters are the richest seafood sources of highly absorbable heme iron, far surpassing finfish.
Heme vs. Non-Heme Iron: The iron in fish and shellfish is heme iron, which is absorbed more efficiently by the body compared to the non-heme iron found in plants.
Sardines and Anchovies: These small, oily fish are also excellent sources of iron, omega-3s, and are typically lower in mercury.
Boosting Absorption: Pairing iron-rich foods with vitamin C (like bell peppers or tomatoes) can enhance absorption, particularly for non-heme sources.
Dietary Considerations: Avoid drinking tea or coffee with iron-rich meals, as the tannins can inhibit absorption.
Cooking Methods: Cooking fish in cast iron can slightly increase its iron content, but standard methods do not significantly impact levels.

The Highest Iron Seafood: It’s Not a Fish

While many people focus on finfish when considering seafood, the real iron champions of the ocean are a type of shellfish known as bivalves. Specifically, clams and oysters contain significantly higher levels of iron than most finfish, making them a potent dietary choice for increasing your mineral intake. The type of iron found in seafood is heme iron, which is absorbed far more effectively by the body than the non-heme iron found in plant sources. This makes clams and oysters exceptionally valuable for those with iron deficiency or anemia.

Clams

Clams are nutritional powerhouses, topping the charts for iron content. A 3.5-ounce (100-gram) serving of cooked clams can contain a remarkable amount of iron. Beyond their high iron levels, clams also provide an excellent source of protein, vitamin B12, and omega-3 fatty acids, offering a comprehensive health boost in a single serving. They can be enjoyed in a variety of ways, from steamed and served with broth to added to pastas and soups.

Oysters

Oysters are another premier source of iron from the sea. Just six medium oysters can provide a significant portion of the daily recommended iron intake. They are also famous for being rich in zinc and vitamin B12. While often eaten raw, oysters can also be steamed, baked, or fried, offering diverse culinary applications to suit different palates.

Top Finfish Sources for Iron

Although shellfish lead the pack, several types of finfish still provide a very good dose of dietary iron. These are often easier to incorporate into daily meals and come with their own unique nutritional profiles.

Sardines: These small, oily fish are typically canned and consumed with their soft, edible bones, which also provide a dose of calcium. A canned serving offers a solid amount of heme iron along with an abundance of omega-3 fatty acids and vitamin B12. Their low position on the food chain means they have low mercury levels, making them a safe choice for regular consumption.
Anchovies: Smaller than sardines, anchovies also pack a significant punch of iron, protein, and omega-3s. They are often sold canned or in paste form and provide a savory umami flavor to a variety of dishes, including pastas and pizzas.
Mackerel: Oily fish like mackerel are prized for their high omega-3 fatty acid content, but they are also a respectable source of iron. Spanish mackerel, in particular, offers a good amount of iron per serving. It is often grilled or pan-seared.
Canned Tuna: Canned light tuna contains iron, making it a convenient option. While fresh tuna also provides iron, the canning process makes it a readily available and shelf-stable source.

Comparison of Iron in Common Seafood


Seafood Type (per 100g)	Heme Iron (mg)	Serving Size	Notes
Clams	~24 mg	3.5 oz (100g)	Exceptionally high iron content
Oysters	7-9 mg	3.5 oz (100g)	Also rich in zinc and B12
Octopus	9.5 mg	3.5 oz (100g)	Another high-iron mollusk
Anchovies	4.6 mg	3.5 oz (100g)	Great source of omega-3s
Sardines (canned)	2.9 mg	3.5 oz (100g)	Includes calcium from bones
Mackerel	1.6 mg	3.5 oz (100g)	Also high in omega-3s
Canned Tuna (in brine)	1.0 mg	3.5 oz (100g)	Convenient and affordable
Salmon (wild Atlantic)	1.03 mg	3.5 oz (100g)	Excellent for omega-3s
Salmon (farmed Atlantic)	0.34 mg	3.5 oz (100g)	Lower in iron than wild

Boosting Iron Absorption and Dietary Considerations

To get the most out of your iron-rich fish, it's important to understand how to maximize absorption. Heme iron is already highly bioavailable, but certain practices can help even more.

Pair with Vitamin C: For non-heme iron sources in your diet, vitamin C significantly enhances absorption. While fish contain heme iron, pairing your seafood with vitamin C-rich vegetables like tomatoes or bell peppers is still beneficial for overall iron intake.
Avoid Inhibitors: Certain substances can hinder iron absorption, such as tannins in tea and coffee and phytates in some nuts and legumes. Consuming these separately from your main iron-rich meal can be helpful.
Cooking Methods: Overcooking red meat can reduce its heme iron content, but for fish, standard cooking methods do not significantly impact the iron levels. However, preparing fish in cast iron cookware can slightly increase its iron content.
Sustainability: Choosing sustainably sourced seafood, especially smaller fish like sardines, is an environmentally conscious decision. Many seafood certification programs, like the Marine Stewardship Council, help identify responsibly harvested options.

Conclusion

When asking "what kind of fish has the most iron in it," the clear answer is that certain types of shellfish, particularly clams and oysters, hold the top spot. While technically not fish, their dense heme iron content makes them a superior choice for addressing iron deficiencies. Several finfish, including sardines, mackerel, and anchovies, also provide good amounts of easily absorbed iron. By incorporating a variety of these seafood options into a balanced diet and being mindful of factors that influence absorption, you can effectively boost your iron levels for better health and energy.

For further reading on nutrient recommendations, consult the U.S. Dietary Guidelines.

Frequently Asked Questions

Yes, tuna can be a good source of iron, especially canned light tuna, though it contains less iron per serving compared to clams or oysters.

Tuna, especially canned, generally has more iron than salmon. For example, some sources show canned tuna with about 1mg per 100g, while farmed salmon has less.

Yes, eating canned sardines with their soft, edible bones provides a higher amount of calcium, but the fish's flesh is where the high heme iron content is primarily found.

Standard cooking methods like grilling or baking do not significantly impact the iron content of fish. To increase the iron, you can cook with cast iron pans.

While iron-rich fish and shellfish can be a valuable part of a diet to combat anemia, it is best to consult a healthcare professional. In some cases of severe iron deficiency, dietary changes alone may not be sufficient, and supplements might be needed.

To maximize iron absorption, pair your fish with foods high in vitamin C, such as bell peppers, citrus fruits, or tomatoes. This is particularly helpful for enhancing the absorption of non-heme iron from other foods in your meal.

Sardines and anchovies are excellent choices for high iron and low mercury. Their small size and position on the food chain mean they accumulate far less mercury than larger fish like tuna.

Yes, all fish contain heme iron, which is found in animal proteins. However, the quantity varies significantly by species.