Is it okay if fish is a little undercooked?

November 8, 2025 •

4 min read

According to the Centers for Disease Control and Prevention (CDC), around 48 million Americans get sick from foodborne illnesses each year, and seafood can be a source if not prepared correctly. The answer to "is it okay if fish is a little undercooked?" is unequivocally no, as even slightly undercooked seafood can harbor harmful pathogens.

Quick Summary

Eating slightly undercooked fish poses significant health risks from bacteria and parasites. Proper cooking to 145°F is crucial for safety, with visual checks like opaqueness and flaking serving as indicators of doneness. Certain groups, including pregnant women and the elderly, face heightened danger.

Key Points

Foodborne Illness Risk: Eating slightly undercooked fish exposes you to dangerous bacteria (like Vibrio and Salmonella) and parasites (like Anisakis), which can cause severe food poisoning.
Safe Internal Temperature: The U.S. FDA recommends cooking fish to an internal temperature of 145°F (63°C) to ensure it is safe to eat.
Visual and Texture Cues: Fish that is fully cooked will turn opaque throughout its flesh and flake easily when prodded with a fork.
At-Risk Groups: Pregnant women, the elderly, young children, and immunocompromised individuals are at a much higher risk for severe complications from foodborne pathogens in undercooked seafood.
Source and Handling Matter: Proper handling, starting from a trusted seafood source and maintaining cold temperatures, is as critical as the cooking process itself.
Flavor vs. Safety: While some prefer the texture of less cooked fish, the safety risks for improperly sourced or handled fish outweigh any perceived flavor benefits for the average consumer.

The Dangers Lurking in Undercooked Fish

Consuming fish that is not thoroughly cooked can expose you to a host of dangerous microorganisms. The primary culprits are bacteria and parasites that thrive in uncooked flesh and can lead to severe foodborne illnesses. This is why public health organizations like the Food and Drug Administration (FDA) and CDC stress the importance of cooking seafood to a safe internal temperature of 145°F. Many people enjoy raw fish dishes like sushi and sashimi, but these carry risks, and reputable establishments mitigate these dangers through careful sourcing and freezing practices. However, for home cooks, any deviation from a fully cooked state is a gamble with your health.

Common Bacteria and Parasites in Raw Fish

Several types of pathogens are commonly associated with raw or undercooked fish:

Vibrio spp.: These bacteria live in coastal waters and are often found in raw or undercooked seafood like shellfish and fish. A Vibrio infection can cause watery diarrhea, abdominal cramps, nausea, and vomiting. Severe cases can lead to dangerous blood infections, particularly in immunocompromised individuals.
Anisakid Nematodes (Worms): These parasites, such as Anisakis simplex, are roundworms that can be ingested when eating raw or undercooked fish or squid. If ingested, they can embed themselves in the stomach or intestinal wall, causing severe abdominal pain, nausea, and vomiting. In some cases, the worms may even be coughed up.
Tapeworms: Certain fish, including wild-caught varieties, can carry tapeworm larvae. Once ingested, these larvae can grow into adult tapeworms inside the human intestine, causing symptoms such as abdominal pain, diarrhea, and weight loss.
Salmonella: A common cause of food poisoning, Salmonella bacteria can contaminate fish during harvesting or handling. Symptoms of a Salmonella infection typically include fever, diarrhea, and stomach cramps.

Who Is Most at Risk?

While anyone can get sick from eating undercooked fish, some groups are at a higher risk of developing severe complications. These sensitive populations include:

Pregnant women: Foodborne illnesses can harm both the mother and the developing fetus.
Young children and older adults: Their immune systems are weaker and may struggle to fight off infections effectively.
Immunocompromised individuals: Those with compromised immune systems due to underlying health conditions are more susceptible to severe and potentially life-threatening infections.

How to Ensure Fish is Cooked Safely

The best way to prevent foodborne illness is to cook fish thoroughly. The FDA's recommended internal temperature of 145°F serves as a critical safety benchmark. While a food thermometer is the most reliable tool, several visual cues can also indicate doneness.

Flaking Test: A classic method is to insert a fork into the thickest part of the fish and twist gently. The fish is done when the flesh flakes easily along its natural lines.

Opaque Appearance: As fish cooks, its flesh transitions from a translucent, shiny color to a solid, opaque one. For example, salmon will turn from deep red to light pink, while cod will become pearly white.

Proper Handling: Safe handling begins before cooking. Purchase fish from a reputable source, ensuring it is properly refrigerated or displayed on ice. Keep raw seafood separate from cooked food and other produce to avoid cross-contamination.

Raw vs. Cooked: A Comparison

To highlight the safety and quality differences, here is a comparison of raw and fully cooked fish.


Feature	Raw (excluding sushi-grade)	Fully Cooked (to 145°F)
Food Safety	High risk of bacterial, parasitic, and viral infections.	Virtually eliminates bacteria and parasites, greatly reducing foodborne illness risk.
Nutrient Absorption	Slightly higher omega-3 content preserved due to lack of heat.	Slightly reduced omega-3 content, but improves protein digestibility for some.
Texture	Soft, tender, and potentially translucent.	Firm, flaky, and opaque throughout the flesh.
Flavor	Delicate, clean, and ocean-like flavor, which can be masked by bacteria.	More robust and developed flavor profile, depending on cooking method and seasoning.
For at-home cooking	Highly risky unless properly sourced and frozen to kill parasites.	The safest and most recommended method for home cooks to prevent illness.

Conclusion: The Risk Is Not Worth the Reward

While a perfectly seared, medium-rare salmon may be a culinary delight, the potential health risks associated with slightly undercooked fish are too significant to ignore for most home cooks. Pathogens like Vibrio and Anisakis can lead to unpleasant and dangerous foodborne illnesses. The only way to guarantee safety is to cook fish to an internal temperature of 145°F. Relying on visual and texture cues like opaqueness and flaking can also help ensure your fish is properly prepared. For at-risk individuals, the elderly, and pregnant women, there is no exception to the 145°F rule. Always prioritize food safety to enjoy delicious seafood without the worry of getting sick. For more guidance on safe food handling, refer to resources like FoodSafety.gov.

Essential Steps for Safe Fish Preparation

Buy fish from a reputable fishmonger or market to ensure proper handling and freshness.
Keep raw fish properly chilled in your refrigerator at 40°F or below, or freeze it promptly.
Use a separate cutting board and utensils for raw fish to prevent cross-contamination.
Use a food thermometer to check that the thickest part of the fish reaches 145°F.
Wash your hands thoroughly with soap and water after handling raw seafood.
When in doubt, throw it out. If a raw or cooked fish has a foul odor, it is best to discard it.
Thaw frozen fish slowly in the refrigerator overnight, rather than at room temperature.

Frequently Asked Questions

If you eat slightly undercooked fish, you are at risk of food poisoning from bacteria like Vibrio or Salmonella, or a parasitic infection from organisms such as Anisakid nematodes or tapeworms. Symptoms can range from mild gastrointestinal distress to severe illness.

Without a thermometer, you can check for doneness by observing if the fish's flesh has turned opaque and if it flakes easily when tested with a fork at its thickest point. If it is still translucent or resists flaking, it needs more cooking time.

While some chefs aim for a medium-rare finish on high-quality salmon, the FDA-recommended safe temperature is 145°F. Eating it below this temperature carries a risk of foodborne illness unless you are certain it is sushi-grade and has been properly frozen to kill parasites.

Symptoms vary but can include nausea, vomiting, diarrhea, abdominal cramps, and fever. Symptoms might appear within hours of eating or be delayed by several days, depending on the specific pathogen involved.

Freezing fish at a certain low temperature for a specific duration can kill parasites. However, it does not kill all bacteria, which is why proper cooking is still necessary for complete safety.

Keep fresh fish properly chilled at 40°F or below, use separate utensils and cutting boards for raw and cooked foods, and wash your hands thoroughly after handling to prevent cross-contamination.

No, cooking does not destroy certain naturally occurring marine toxins, such as ciguatoxins and scombrotoxins. The best prevention is to avoid fish known to carry these toxins and to ensure proper refrigeration from the time of catch.