Most healthy adults can safely eat raw fish two to three times per week, as long as they choose low-mercury species and source fish that has been properly handled. The main limiting factor isn’t bacteria or parasites (those are managed through freezing and sourcing), but mercury, which builds up in your body over time. Your weekly budget depends largely on which fish you’re eating.
Mercury Is the Real Frequency Limiter
The form of mercury found in fish, methylmercury, has a half-life of about 80 days in the human body. That means if you eat a high-mercury meal today, half of that mercury is still circulating nearly three months later. Eat high-mercury fish several times a week and levels stack up faster than your body can clear them. This is why frequency matters more for raw fish than for most other foods.
Federal dietary guidelines recommend 8 to 12 ounces of low-mercury seafood per week, which works out to two or three servings. A raw fish serving is about 4 ounces. If you stick to low-mercury options like salmon (0.022 ppm mercury), shrimp (0.009 ppm), or squid (0.024 ppm), three servings a week keeps you well within safe limits while delivering meaningful amounts of omega-3 fatty acids.
Higher-mercury fish tighten that budget fast. Fresh yellowfin tuna averages 0.354 ppm, and bigeye tuna hits 0.689 ppm. Swordfish and shark approach 1.0 ppm. If you eat yellowfin or albacore tuna as sashimi, one 4-ounce serving per week should be your maximum, and that serving replaces your other fish for the week rather than adding to it.
Low-Mercury Fish You Can Eat More Often
Not all sushi is created equal from a mercury standpoint. These species are common in raw preparations and sit at the bottom of the mercury scale:
- Salmon: 0.022 ppm. One of the safest and most omega-3-rich choices. You could eat it three times a week without concern.
- Shrimp: 0.009 ppm. Extremely low mercury, though less commonly eaten raw outside of certain preparations.
- Squid: 0.024 ppm. Very low mercury and widely used in sashimi.
- Scallop: 0.003 ppm. The lowest mercury level of any commonly tested seafood.
By contrast, these popular sushi fish carry enough mercury that you need to limit them:
- Yellowfin tuna (ahi): 0.354 ppm. One serving per week max.
- Bigeye tuna: 0.689 ppm. Limit to occasional consumption.
- Snapper: 0.166 ppm. Moderate range, fine once a week alongside a lower-mercury option.
- Mackerel (king): 0.73 ppm. Best avoided for frequent raw consumption. Atlantic mackerel, at 0.05 ppm, is a much safer choice.
How Parasites Are Controlled
Parasitic worms, particularly Anisakis, are naturally present in many wild ocean fish. In populations that regularly eat raw fish without proper preparation, exposure rates can be strikingly high. A study of raw fish consumers in the Sangihe Islands of Indonesia found that over 52% tested positive for Anisakis antibodies, with certain species of raw tuna carrying a dramatically elevated risk.
In the U.S. and most developed markets, this risk is managed through freezing. The FDA’s guidelines require fish intended for raw consumption to be frozen at -4°F (-20°C) for at least 7 days, or blast-frozen at -31°F (-35°C) until solid and stored for 15 to 24 hours depending on temperature. This kills parasites effectively. Reputable sushi restaurants and fish markets follow these protocols, which is why parasitic infections from sushi are rare in the U.S. despite millions of servings consumed weekly.
“Sushi Grade” Doesn’t Mean What You Think
There is no FDA-regulated definition of “sushi grade” or “sashimi grade.” These are marketing terms. What actually matters is whether the fish was frozen according to the FDA’s parasite-destruction guidelines. A trustworthy fishmonger or restaurant can tell you whether their fish was frozen to the required specifications. If they can’t answer that question, that’s a red flag. When buying fish to eat raw at home, ask specifically about the freezing protocol rather than relying on a label.
Bacterial Risks at Every Serving
Unlike mercury, bacterial contamination isn’t a cumulative problem. It’s a per-serving risk. The most concerning bacteria in raw seafood are Vibrio species, which cause an illness called vibriosis. Most cases come from raw shellfish like oysters rather than fin fish, but the risk applies broadly to any raw seafood. Vibrio vulnificus infections are rare but severe: about 1 in 5 people who contract this particular species die, sometimes within a day or two.
For healthy adults with normal immune function, the bacterial risk from properly handled raw fin fish is low. But frequency does increase your cumulative exposure to that small risk. Eating raw fish twice a week at a reputable restaurant is a very different proposition from eating it daily from inconsistent sources. Freshness, cold-chain handling, and the reputation of where you buy all matter more than any specific number of servings.
Handling Raw Fish at Home
If you prepare raw fish at home, cross-contamination is the most common way things go wrong. Use a dedicated cutting board for raw seafood, separate from the one you use for produce and cooked foods. Wash all surfaces, knives, and utensils with hot soapy water immediately after contact with raw fish. Store raw fish in sealed containers on the lowest shelf of your refrigerator so juices can’t drip onto other foods.
If you marinate raw fish (for poke bowls, for example), never reuse that marinade on anything else unless you boil it first. And if you don’t have two cutting boards, prep your vegetables and other ingredients first, then clean the board thoroughly before handling the fish.
Who Should Avoid Raw Fish Entirely
Pregnant and breastfeeding people should skip raw fish altogether, regardless of species or sourcing. The FDA and major medical organizations are clear on this point: the risk of bacterial and parasitic infection, even if small, is not worth taking during pregnancy. Cooked fish is still recommended, with 8 to 12 ounces of low-mercury seafood per week and a 6-ounce weekly cap on albacore tuna.
Young children, older adults, and anyone with a weakened immune system (from conditions like liver disease, diabetes, cancer treatment, or HIV) face significantly higher risks from Vibrio and other raw-seafood pathogens. For these groups, cooking fish to an internal temperature of 145°F eliminates the bacterial risk while preserving the nutritional benefits.
A Practical Weekly Plan
For a healthy adult who loves sushi and sashimi, a reasonable weekly pattern looks like this: two to three servings of raw fish, each about 4 ounces, totaling 8 to 12 ounces. Lean toward salmon, shrimp, scallops, and squid as your base. If you want tuna, make it one of your servings rather than all of them, and favor skipjack (0.144 ppm) over bigeye (0.689 ppm) when you can.
This approach lands you in the sweet spot where you’re getting the cardiovascular benefits of omega-3 fatty acids, keeping mercury exposure well below concerning levels, and managing your cumulative risk of foodborne illness. The Mayo Clinic puts it simply: for most adults, the benefits of eating fish outweigh the risks of mercury exposure, as long as you’re choosing wisely and not overdoing high-mercury species.