What Is the Best Fish for Keto Diet? An In-Depth Guide

November 7, 2025 •

4 min read

According to the Dietary Guidelines for Americans, adults should consume 8 to 10 ounces of seafood per week, making it a healthy protein staple. This raises a key question for those in ketosis: what is the best fish for keto diet, prioritizing healthy fats, high protein, and minimal carbs?

Quick Summary

The ideal fish for a keto diet are either high in healthy fats, particularly omega-3s, or lean sources of high-quality protein with negligible carbs. Top choices include fatty fish like salmon, mackerel, and sardines, as well as leaner options such as cod and mahi-mahi.

Key Points

Wild-caught salmon: Excellent source of omega-3s and vitamin D, perfect for meeting keto fat macros.
Mackerel and sardines: Highly nutritious, affordable fatty fish rich in omega-3s, vitamin D, and selenium.
Lean white fish: Cod, mahi-mahi, and halibut provide high-quality protein with negligible carbs, but require added fats for keto optimization.
Low-carb shellfish: Shrimp, lobster, and crab offer zero-carb protein, while oysters have a minimal but trackable carb count.
Keto-friendly cooking: Avoid breading and sugary marinades; use healthy fats like olive oil, butter, or coconut oil to cook your fish.
Nutrient powerhouse: Fish provides essential nutrients like B vitamins, selenium, and potassium, which are beneficial for overall health.
Mercury awareness: Limit intake of larger predatory fish like swordfish and certain tunas due to potential mercury levels, and opt for smaller species more frequently.

Fish on a Keto Diet: The High-Fat Advantage

Fish and shellfish are excellent for a ketogenic diet because most varieties contain almost zero carbohydrates. However, their macronutrient profile—specifically the ratio of fat to protein—can vary significantly. For a high-fat, low-carb diet like keto, prioritizing fattier fish can help you meet your daily fat intake goals while providing vital omega-3 fatty acids.

The All-Stars: Fatty Fish for Maximum Benefits

Fatty, or oily, fish are dense in omega-3s, which are crucial for brain and heart health, and can even help manage blood sugar levels. These types of fish are perfect for a keto diet as they support ketosis by providing a high concentration of healthy fats.

Salmon: Often considered the gold standard for keto seafood, salmon is rich in heart-healthy omega-3s, B vitamins, and vitamin D. Wild-caught salmon is generally preferred for its potentially higher nutrient content. A 3.5 oz serving of Atlantic salmon can contain around 12g of fat with no carbs.
Mackerel: An underrated and affordable option, mackerel is another oily fish packed with omega-3s, vitamin D, and selenium. Its robust flavor stands up well to marinades and bold seasonings. A 3 oz serving provides an impressive 2990 mg of omega-3.
Sardines and Anchovies: These small, oily fish are nutrient powerhouses and can be eaten whole, providing calcium from the bones. They are excellent sources of omega-3s, B vitamins, and selenium, with minimal environmental toxins. They can be enjoyed straight from the can or added to salads and sauces.
Tuna: Whether fresh or canned in olive oil, tuna is a versatile and low-carb fish. It's a great source of protein, vitamin D, and omega-3s, although larger varieties may have higher mercury levels. It's best to enjoy it in moderation and focus on smaller species or fresh fillets.

Lean Fish: High Protein, Low Fat

While fatty fish are emphasized on keto, leaner white fish still make excellent additions to a meal plan, especially when paired with a separate source of healthy fat like olive oil, avocado, or butter.

Cod: This mild-flavored white fish is high in protein and a good source of B12 and omega-3s. It's low in calories and carbohydrates, making it a versatile choice that absorbs other flavors easily.
Mahi-Mahi: A sweet, firm-textured white fish, mahi-mahi is low in fat but high in protein. It is ideal for grilling or pan-frying and pairs well with rich, keto-friendly sauces.
Halibut and Flounder: These flaky white fish offer a delicate, mild taste with high protein content and very few carbs. They are easily adaptable to various keto-friendly preparations.

Shellfish: Protein-Packed and Mostly Carb-Free

Most shellfish are naturally low in carbohydrates, making them a great keto option. However, it's important to be mindful of the carb content in some types, like oysters and octopus, and to track them if necessary.

Shrimp and Prawns: These are among the most popular and easiest shellfish to prepare, with virtually no carbs. They are high in protein and can be sautéed in butter or olive oil for added healthy fats.
Crab and Lobster: High in protein and almost completely carb-free, these are a delicious keto-friendly indulgence. They are perfect when served with melted butter.
Mussels: These offer a good amount of protein and omega-3s for a low carb count, though they do contain some carbs that should be monitored.

Cooking Fish for the Best Keto Results

Proper preparation is key to ensuring your fish meals stay keto-compliant and nutritious. Avoid high-carb coatings and instead focus on methods that enhance flavor with healthy fats.

Healthy Fats are your Friend: Cook your fish in keto-friendly fats like butter, olive oil, or coconut oil. These add flavor and help you meet your fat macro goals.
Avoid Breading and Sugary Sauces: Traditional flour-based breading is a carb trap and should be avoided. Use almond flour or coconut flour for a keto-friendly breading instead. Also, be mindful of hidden sugars in marinades or sauces.
Low-Temperature Cooking: High-heat cooking can damage the delicate omega-3s in fatty fish. Aim for baking or pan-frying at around 160-175°C (320-350°F) to preserve nutrients.

Comparison of Keto-Friendly Fish


Fish Type	Carbs (per 100g serving)	Fat Content	Omega-3s (Richness)	Notes
Wild Salmon	0g	High (approx. 12g fat)	Excellent	Highest omega-3 content; versatile.
Mackerel	~0g	High	Excellent	Affordable, rich in vitamin D.
Sardines	0g	High (approx. 8g fat)	Excellent	Great for calcium; minimal mercury.
Tuna	0g	Moderate-High (fresh)	Excellent	Versatile; limit due to mercury concerns.
Cod	0g	Very Low (approx. 0.7g fat)	Moderate	Lean protein; best cooked with added fat.
Mahi-Mahi	0g	Very Low	Moderate	Lean protein; great for grilling.
Shrimp	0g	Very Low	Low	Versatile; must be paired with healthy fats.
Oysters	4g (variable)	Low	Moderate	Watch carb count; high in zinc.

Conclusion: Your Keto Fish Strategy

When choosing the best fish for a keto diet, a balanced approach is best. Incorporate fatty fish like salmon and mackerel for their high omega-3 content and fat density. Supplement with leaner, high-protein options like cod and mahi-mahi, ensuring you add healthy fats during cooking. With minimal carbohydrates across the board, seafood provides a delicious and nutrient-rich way to stay in ketosis and add variety to your meals. By focusing on nutrient-dense options and proper preparation, you can easily make fish a healthy and rewarding part of your ketogenic journey. For more guidance on a keto diet and the best food choices, resources like Healthline offer comprehensive information.

Disclaimer: Please consult a healthcare professional before starting any new diet.

Frequently Asked Questions

Most fish and shellfish are very keto-friendly because they contain almost no carbohydrates. However, it's wise to be mindful of certain shellfish, like oysters and octopus, which contain a small number of carbs that should be tracked to stay within your daily limit.

Oily, fatty fish are your best choice for a high-fat keto diet. Salmon, mackerel, and sardines are particularly high in healthy omega-3 fatty acids, which are beneficial for heart and brain health.

To keep your fish keto-friendly, cook it with healthy fats. Bake, grill, or pan-fry with olive oil, coconut oil, or butter. Avoid traditional flour-based breading, opting for low-carb alternatives like almond flour instead.

Yes, canned fish like tuna, salmon, and sardines are great keto options. Canned varieties packed in olive oil can even help increase your healthy fat intake. Just check the label for any added sugars or high-carb ingredients.

Larger, predatory fish like swordfish and some tuna varieties tend to have higher mercury levels. For this reason, it's often recommended to limit their consumption and prioritize smaller, fattier fish like sardines and mackerel.

Shellfish like shrimp, crab, and lobster are virtually carb-free. However, be aware that oysters and mussels contain a small amount of carbohydrates, so you'll need to account for them in your daily macros.

When preparing lean fish, you can increase your fat intake by cooking it in butter or olive oil. Serving it with a keto-friendly sauce, such as a lemon-garlic butter sauce or a creamy avocado dip, is also a great strategy.