Yes, is any fish low in potassium? Low-Potassium Seafood Options and Diet Tips

December 8, 2025 •

3 min read

According to the National Kidney Foundation, the amount of potassium and phosphorus in fish varies by type. This means that while some fish, like wild salmon and halibut, are naturally higher in potassium, other types like flounder, cod, and specific preparations of tuna offer lower-potassium alternatives.

Quick Summary

Several fish varieties, such as flounder, sole, catfish, and canned light tuna packed in water, have low potassium levels. Cooking methods like boiling and draining can further reduce potassium content in seafood and other foods for those on restricted diets.

Key Points

Low-Potassium Choices: Opt for flounder, cod, catfish, sole, and canned light tuna (in water) for lower potassium content.
Avoid High-Potassium Fish: Be mindful of fish like wild salmon, halibut, and mackerel, which naturally contain higher levels of potassium.
Cooking Methods Matter: Boiling fish in excess water and then draining it can effectively reduce its potassium content.
Canned Tuna Strategy: Always drain and rinse canned light tuna packed in water to lower both potassium and sodium levels.
Portion Control: Even with low-potassium options, proper portion sizes are important for managing dietary intake, especially on a restricted diet.

Understanding Potassium in Fish

Potassium is a crucial mineral for nerve function, muscle contraction, and maintaining a normal heart rhythm. However, for individuals with compromised kidney function or those on a low-potassium diet, managing intake is vital to prevent a condition called hyperkalemia, or high blood potassium. While many healthy foods, including some fish, contain potassium, careful selection and preparation can allow seafood to remain a part of a balanced diet.

Low-Potassium Fish Options

When aiming for a low-potassium diet, prioritizing certain fish is key. The following fish are known to have lower potassium content per serving, making them excellent choices:

Canned Light Tuna (in water): A 3-ounce portion can contain around 201 mg of potassium, a considerably lower amount than many other fish. Rinsing it before use can further reduce sodium levels.
Flounder and Sole: Cooked flounder or sole typically provides a low-potassium count, with a 3-ounce serving having approximately 167 mg.
Cod: Cooked Atlantic cod is another good choice, offering around 207 mg of potassium per 3-ounce serving.
Catfish: This fish is also noted as being among the lower-potassium options available.
Shrimp: This shellfish can be a suitable low-potassium choice, with a 3-ounce serving of cooked shrimp containing roughly 220 mg.
Orange Roughy and Sea Bass: These fish are also considered lower-potassium options.

Cooking Methods to Reduce Potassium

For those needing to strictly limit potassium, preparation methods can further decrease the mineral's levels in fish and other foods.

Soaking: For some foods, cutting them into small pieces and soaking them in a large volume of water for at least four hours can remove a significant amount of potassium. While most applicable to vegetables, the principle of soaking can be considered for some fish, though not universally required for the low-potassium varieties.
Boiling and Draining: Boiling fish in plenty of water and then draining the liquid is another effective method. The minerals, including potassium, leach out into the cooking water. It is crucial to discard this liquid and not use it in sauces or gravies.
Rinsing Canned Fish: For canned light tuna packed in water, draining and rinsing the fish for a minute or two can significantly reduce both potassium and sodium levels.

Comparison of Fish Potassium Content

This table illustrates the difference in potassium levels between low-potassium fish and some higher-potassium counterparts, based on approximate values for a 100g (3.5oz) cooked serving.


Fish Type (Cooked)	Approximate Potassium (mg/100g)	Notes
Flounder	197	Excellent low-potassium choice.
Canned Light Tuna (in water, drained)	179	One of the lowest options; good for convenience.
Shrimp	259	A good low-potassium shellfish option.
Cod	207	Solid low-potassium choice, versatile for recipes.
Wild Salmon	400-500	Higher in potassium, requires portion control.
Halibut	~480	High potassium, best to avoid on a strict renal diet.
Mackerel	558	High potassium, high in omega-3s but needs careful monitoring.

Integrating Low-Potassium Fish into Your Diet

Including low-potassium fish in your meal plan can be simple and delicious.

Baked Cod with Herbs: A simple recipe involves baking a cod fillet with olive oil, lemon zest, garlic, and herbs like dill or parsley. This enhances flavor without adding high-potassium ingredients.
Flounder Stir-Fry: Quickly stir-fry small pieces of flounder with low-potassium vegetables like onions and bell peppers, adding a low-sodium soy sauce for flavor.
Tuna Salad: Prepare a classic tuna salad using rinsed, canned light tuna, low-sodium mayonnaise, and diced celery. Serve on a low-potassium bread or with lettuce wraps.

Conclusion

While it's a common misconception that all fish are high in potassium, many excellent low-potassium options exist. Choices like flounder, cod, and canned light tuna can be safely included in a renal or low-potassium diet. Furthermore, employing specific cooking techniques like boiling and draining can help manage potassium levels in food. By selecting the right types of fish and preparing them appropriately, individuals can enjoy the nutritional benefits of seafood without compromising their dietary restrictions. Always consult a healthcare professional or registered dietitian for personalized dietary advice. For more detailed information on managing a renal diet, you can visit the DaVita website for helpful resources and recipes.

Frequently Asked Questions

Among the commonly available fish, flounder and canned light tuna (packed in water) are often cited as some of the lowest in potassium. For example, a 3-ounce serving of cooked flounder has about 167 mg of potassium, and rinsed canned light tuna has around 201 mg for the same portion.

No, not all canned fish are high in potassium. The potassium content depends on the type of fish and how it is packed. Canned light tuna packed in water tends to be lower in potassium than fresh tuna. However, some canned fish with bones, like sardines, can be very high in phosphorus.

No, wild salmon is a potassium-rich food. A 3.5-ounce serving of wild salmon can contain more potassium than a banana. It can still be included in a low-potassium diet with careful portion control and in conjunction with other low-potassium foods.

Yes, cooking methods can help. Boiling fish in a generous amount of water and discarding the cooking liquid will cause some of the potassium to leach out, effectively reducing the mineral content.

There is a notable difference. Wild salmon contains more potassium than farmed salmon. For example, a 3.5-ounce serving of wild salmon offers 13% of the Daily Value (DV) for potassium, while the same amount of farmed salmon contains 8% of the DV.

Yes, shrimp is a suitable option for those on a low-potassium diet. A 3-ounce serving of cooked shrimp has approximately 220 mg of potassium, making it a viable and tasty protein source.

For a low-potassium diet, opt for canned light tuna packed in water. Be sure to drain and rinse it thoroughly to reduce both potassium and sodium levels.