What Fish is the Lowest in Potassium? A Guide to Low-Potassium Seafood

December 1, 2025 •

4 min read

According to nutrition data, some seafood, particularly certain shellfish like clams, contains remarkably low levels of potassium. This guide reveals exactly what fish is the lowest in potassium, providing details on specific species to help you make informed dietary choices for kidney health or other needs.

Quick Summary

This article examines various seafood options to identify the lowest potassium fish. It details specific shellfish like clams and shrimp, highlights low-potassium finfish such as flounder and cod, and provides a comparison table.

Key Points

Clams are exceptionally low in potassium: With only 58 mg per 100g, clams are one of the best seafood choices for managing potassium intake.
Shrimp is another low-potassium shellfish: Containing just 101 mg per 100g, shrimp is a lean, protein-rich option for a restricted diet.
Flounder and sole are top low-potassium finfish: These fish are known for their low potassium content, with flounder at 197 mg per 100g.
Canned light tuna in water is a good option with preparation: Choose low-sodium varieties and rinse the tuna to minimize both sodium and potassium intake.
Cod is a moderate, not extremely low, potassium fish: While a healthy choice, portion control is necessary for cod due to its moderate potassium levels.
Always check for additives in canned fish: Some canned fish, especially those with bones, contain high levels of phosphorus and should be avoided on renal diets.
Preparation is key for managing potassium: Simple cooking methods like baking or steaming are best, and low-sodium seasonings should be used.

Understanding Potassium in Your Diet

For individuals with kidney disease or other medical conditions, managing dietary potassium is a critical component of treatment. While fish is a healthy, high-protein food, its potassium content can vary significantly between species. Knowing which options are the lowest is key to managing a low-potassium diet effectively. Most meats and seafood contain moderate to high levels of potassium, but there are exceptions, especially within the shellfish category. Fresh, unprocessed fish is generally a better choice than processed or canned versions with added preservatives, but even then, careful selection is necessary.

The #1 Contenders: Shellfish with the Lowest Potassium

When aiming for the absolute lowest potassium seafood, certain shellfish consistently rank at the top. Their low-calorie, high-protein profiles make them an excellent choice for a restrictive diet.

Clams

With only 58 milligrams of potassium per 100-gram serving, clams are one of the lowest potassium seafood options available. They are a versatile addition to soups, pasta, and stir-fries, offering a distinct briny flavor without a significant potassium load. When preparing, ensure they are cooked thoroughly and avoid high-sodium broths or seasoning mixes.

Shrimp

Coming in slightly higher than clams but still remarkably low, shrimp contains around 101 milligrams of potassium per 100-gram serving. Shrimp is a popular, lean protein that can be grilled, boiled, or sautéed. However, be cautious with pre-seasoned or frozen varieties, as they may contain higher amounts of sodium or phosphate additives.

Finfish with Surprisingly Low Potassium Levels

Beyond shellfish, several common types of finfish also have a relatively low potassium count, making them suitable for many dietary restrictions. These options provide lean protein and beneficial nutrients.

Flounder and Sole

Both flounder and sole are excellent choices for a low-potassium diet. A 3.5-ounce (100g) serving of cooked flounder contains just 197 milligrams of potassium, while a 3-ounce serving has an even lower 167 milligrams. Their mild flavor and delicate texture make them easy to incorporate into a variety of dishes.

Cod and Haddock

Often grouped with other low-potassium options, cod and haddock offer moderate but manageable potassium levels. A 3.5-ounce serving of cooked haddock contains 351 milligrams of potassium, while a 3-ounce serving of cooked Atlantic cod has 207 milligrams. These are good choices, but serving size must be carefully controlled, especially for those with very strict potassium limits.

Canned Light Tuna in Water

For convenience, canned light tuna can be a surprisingly good option, provided you choose the right kind. A 3.5-ounce (100g) serving of canned light tuna in water contains 176 milligrams of potassium. It is crucial to select low-sodium versions and rinse the tuna thoroughly to remove excess sodium.

Comparison of Potassium in Common Fish and Shellfish


Seafood Type	Potassium (mg per 100g serving)	Notes
Clams	58	Exceptionally low in potassium.
Shrimp	101	A great low-potassium protein source.
Canned Light Tuna (in water)	176	Choose low-sodium and rinse well.
Flounder	197	Excellent finfish choice with a mild flavor.
Oysters	193	Another low-potassium shellfish option.
Atlantic Cod	207 (for 3oz)	Moderately low; good for managed diets.
Haddock	351	Higher than flounder but still manageable with portion control.
Salmon	439	Higher in potassium; requires careful planning on a renal diet.

Considerations for a Low-Potassium Fish Diet

Following a low-potassium diet requires attention to detail beyond just choosing the right fish. Portion control is essential, as even a lower-potassium fish can contribute a significant amount if eaten in large quantities.

Cooking Methods: The preparation of fish can also impact its nutrient content. Steaming, baking, or grilling is generally preferable to frying, as frying can add unnecessary fats and potentially alter nutrient profiles. Always cook fish fresh if possible to avoid additives found in some frozen or processed products.
Canned Fish: When choosing canned fish, always read the labels. High-sodium versions and those packed with bones (like some sardines) should be avoided on a restrictive diet due to high sodium and phosphorus content.
Accompaniments: Pair your low-potassium fish with other low-potassium sides, such as rice, corn, or low-potassium vegetables like carrots or lettuce. This helps balance the meal and keep your overall potassium intake in check.

How to Prepare Low-Potassium Fish

Rinse Canned Fish: For options like canned light tuna, rinse the fish in fresh water for at least a minute to reduce sodium content by a significant amount.
Steam, Don't Boil: When cooking, steaming or baking can help retain flavor and nutrients without adding extra fat or preservatives. Boiling can sometimes leach minerals, but steaming is a gentle and effective method.
Season with Herbs: Use fresh herbs, garlic powder, and mild spices instead of high-sodium salt or pre-made spice blends to add flavor.
Create Simple Marinades: A simple marinade of olive oil, lemon juice, and fresh dill can elevate the flavor of flounder or sole without adding potassium.
Combine with Low-K Sides: Serve your fish alongside low-potassium sides to maintain dietary balance. A simple steamed flounder with a side of white rice and steamed carrots is a delicious and safe meal.

Conclusion

For those needing to reduce potassium intake, knowing what fish is the lowest in potassium is crucial. Shellfish like clams and shrimp are the clear winners, with very low potassium counts. Among finfish, flounder and sole are excellent choices, with canned light tuna in water also being a viable, convenient option when prepared correctly. By understanding the potassium differences between species and practicing mindful preparation and portion control, individuals can continue to enjoy delicious and healthy seafood while adhering to their dietary restrictions. Always consult a healthcare provider or a registered dietitian for personalized advice regarding a low-potassium diet. DaVita provides comprehensive resources for managing kidney health.

Frequently Asked Questions

Among common seafood, clams contain the lowest potassium, with just 58 milligrams per 100-gram serving. Shrimp and canned light tuna in water are also very low in potassium.

Cod is generally considered a low to moderate-potassium fish. While it is a healthy option, it is not as low in potassium as clams or shrimp. Portion control is essential for cod on a very strict low-potassium diet.

Yes, but with caution. Choose canned light tuna packed in water and ensure it is a low-sodium variety. Always rinse it thoroughly to further reduce the sodium and potassium content.

For those with kidney disease, the best fish are typically the ones lowest in potassium and phosphorus, such as flounder, sole, and shellfish like clams and shrimp. Always consult a healthcare provider or a renal dietitian for specific recommendations.

While clams and shrimp are notably low in potassium, not all shellfish have the same levels. For example, lobster has moderate potassium. It is always best to check specific nutritional information.

No, cooking methods typically do not significantly reduce the potassium content in fish. Baking, steaming, or grilling can help avoid adding extra sodium, but the base potassium level of the fish remains largely unchanged.

Look for fresh, unprocessed fish like flounder, sole, or cod. For canned options, choose 'light tuna in water' with 'low sodium' clearly labeled. Avoid fish packed in oil or with high sodium marinades.