Tuna contains zero carbohydrates. Whether raw, grilled, or canned, plain tuna is purely protein and fat with no carbs at all. A 100-gram serving of raw skipjack tuna has 22 grams of protein, about 1 gram of fat, and 0 grams of carbohydrate. That makes it one of the most carb-free foods you can eat.
The carbs only show up when tuna gets combined with other ingredients, and the differences can be dramatic depending on how it’s prepared.
Plain Tuna Has Zero Carbs in Every Form
Fresh tuna steaks, whether yellowfin, skipjack, or albacore, contain no carbohydrates regardless of how you cook them. Grilling, baking, searing, or eating it raw as sashimi doesn’t change that number. The same applies to canned tuna. Both water-packed and oil-packed canned tuna have 0 grams of carbs per serving. The only real difference between those two options is calories: a 5-ounce can packed in water runs about 120 calories, while the same amount packed in oil jumps to around 280 calories. The carb count stays at zero either way.
Because tuna has no carbohydrates at all, it also has a glycemic index and glycemic load of zero. It produces no measurable blood sugar response, which makes it a reliable protein source for people managing diabetes or following low-carb and ketogenic diets.
Where the Carbs Sneak In
Tuna itself isn’t the problem. It’s everything that tends to come with it. The carb content of a tuna dish can range from zero to well over 40 grams depending on preparation.
Sashimi keeps things simple. Thin slices of raw tuna with soy sauce and wasabi add virtually no carbohydrates.
Nigiri is a different story. Two pieces (about 100 grams) of tuna nigiri contain roughly 12 grams of carbs, all from the pressed rice underneath the fish.
Spicy tuna rolls climb higher. A 100-gram portion (two to three pieces) packs about 16.7 grams of carbs from the sushi rice, and often more if the roll includes sauces with added sugar.
Tuna salad varies widely based on what goes into the bowl. A basic recipe with pickled cucumbers, corn, bell pepper, eggs, and a bit of mayo and yogurt comes out to roughly 10 grams of carbs per serving, mostly from the vegetables and corn. Swap in sweet relish, dried cranberries, or serve it on bread, and you can easily triple that number.
Tuna melts and casseroles bring bread, pasta, crackers, or cheese sauces into the picture, pushing carb counts into the 30 to 50 gram range per serving depending on the recipe.
Why Tuna Works for Low-Carb Diets
Tuna’s nutritional profile is almost entirely protein. At 22 grams of protein and just 1 gram of fat per 100-gram serving (for lean varieties like skipjack), it’s one of the highest protein-to-calorie ratios available in any whole food. Fattier species like bluefin carry more fat and omega-3s but still have zero carbs.
For ketogenic diets, tuna works well as a protein base, though its low fat content means you may need to pair it with added fats like olive oil, avocado, or mayo to hit your macronutrient targets. Healthline lists tuna alongside salmon, anchovies, and sardines as strong additions to a keto diet thanks to its protein quality and omega-3 content.
How Much Tuna You Can Safely Eat
Since tuna fits so neatly into low-carb eating plans, it’s worth knowing the recommended limits. Mercury is the main concern, and the FDA’s current guidance draws a clear line between tuna types.
Canned light tuna (usually skipjack) falls in the “Best Choices” category, meaning you can safely eat two to three servings per week. Albacore or white tuna, both canned and fresh, lands in the “Good Choices” tier, where the recommendation drops to one serving per week. A serving is 4 ounces, roughly the size of your palm.
Rotating between canned light tuna during the week and a fresh tuna steak occasionally gives you the flexibility to enjoy it regularly without exceeding mercury guidelines. Pairing tuna with low-carb sides like leafy greens, cucumbers, or avocado keeps the entire meal close to zero carbs while adding fiber and healthy fats that tuna alone doesn’t provide.