Fish is one of the lowest-carb foods you can eat. A 3-ounce serving of plain cod, salmon, tuna, or tilapia contains zero grams of carbohydrates. This applies to virtually all fresh, unprocessed fish, making it an ideal protein source for keto, low-carb, and other carbohydrate-restricted diets.
Carb Counts for Common Fish
According to FDA nutrition data, the following fish all contain 0 grams of total carbohydrate per 3-ounce cooked serving:
- Cod: 0g carbs
- Atlantic, coho, sockeye, and chinook salmon: 0g carbs
- Chum and pink salmon: 0g carbs
- Tuna: 0g carbs
- Tilapia: 0g carbs
This pattern holds across nearly every fin fish species. Whether you’re eating halibut, trout, sardines, catfish, or pollock, plain fish is essentially a zero-carb food. The FDA notes that seafood provides “negligible amounts” of dietary fiber and sugars as well, so there are no hidden carbs to worry about.
How Cooking Methods Change the Carb Count
Plain fish has zero carbs, but what you coat it in can change that dramatically. A 100-gram portion of steamed fish contains 0 grams of carbohydrates. That same portion deep-fried in batter jumps to 18 grams of carbs. The flour, breadcrumbs, and beer batter used in frying are the source of those carbs, not the fish itself.
To keep fish low-carb, stick with grilling, baking, broiling, poaching, or steaming. Season with herbs, lemon, butter, olive oil, or spices. All of these add flavor without adding carbohydrates. If you want a crispy coating, almond flour or crushed pork rinds are common low-carb substitutes for traditional breading.
Processed Fish Products to Watch
Not everything that looks like fish at the grocery store is zero-carb. Imitation crab (surimi) is one of the biggest surprises for low-carb shoppers. It’s made from processed white fish blended with starches and sugars, and a single 3-ounce serving contains about 10 grams of carbohydrates. If you’re tracking carbs closely, always check the label on any surimi-based product, including many “crab” sticks, seafood salads, and sushi rolls labeled as California rolls.
Canned fish can also carry hidden carbs depending on the sauce. Plain canned tuna or sardines packed in water or oil remain zero or near-zero carb. But sardines in tomato sauce contain around 3 grams of carbohydrate per serving, with about 2 grams coming from sugar (1 gram of that added sugar). Teriyaki-glazed, honey-smoked, or mustard-packed varieties will be higher. The simplest rule: the plainer the can, the fewer the carbs.
Why Fish Works Well on a Low-Carb Diet
Beyond being carb-free, fish delivers high-quality protein and healthy fats that complement a low-carb eating pattern. Fatty fish like salmon, sardines, trout, herring, and mackerel are rich in omega-3 fatty acids (EPA and DHA), which support heart and brain health. These happen to also be among the fish lowest in mercury, making them a smart choice on multiple levels.
The Dietary Guidelines for Americans recommend eating about 8 ounces of seafood per week for a standard 2,000-calorie diet. That’s roughly two meals. Pregnant and breastfeeding women are encouraged to eat 8 to 12 ounces weekly, choosing varieties lower in mercury such as salmon, shrimp, pollock, canned light tuna, and farmed catfish.
Best Low-Carb, Low-Mercury Fish Choices
If you’re eating fish regularly on a low-carb diet, mercury exposure is worth considering. The good news is that many of the healthiest, most omega-3-rich fish are also the lowest in mercury. California’s Office of Environmental Health Hazard Assessment identifies these as lower-mercury options:
- Salmon
- Trout
- Sardines
- Cod
- Tilapia
- Sole
- Pollock
- Farmed catfish
- Shrimp
Every one of these is zero-carb when prepared without breading or sugary sauces. For the best combination of omega-3 content and low mercury, salmon, trout, sardines, and herring stand out. Rotating among several types gives you nutritional variety while keeping mercury intake low.