What Happens If You Eat Fish with Mercury? The Health Risks Explained

December 11, 2025 •

4 min read

According to the World Health Organization, mercury is one of the top ten chemicals of major public health concern. Therefore, understanding what happens if you eat fish with mercury is crucial for minimizing risks and protecting your health, especially for sensitive populations.

Quick Summary

Consuming fish with high levels of methylmercury can cause significant health problems, particularly neurological and developmental damage in vulnerable populations. It is important to know which fish to choose and which to limit to reduce health risks and safely enjoy the nutritional benefits of seafood. Knowing the symptoms of mercury exposure and seeking medical advice when concerned is also essential.

Key Points

Methylmercury Dangers: High levels of methylmercury, a neurotoxin found in fish, can cause serious harm to the central nervous system.
Vulnerable Populations: Pregnant women, nursing mothers, and young children are most at risk due to the impact on the developing brain.
Key Symptoms: Signs of poisoning include numbness or tingling, coordination problems, vision issues, and emotional changes.
Choose Low-Mercury Fish: Opt for 'Best Choices' like salmon, sardines, and tilapia to minimize exposure while still gaining nutritional benefits.
Avoid High-Mercury Fish: Limit or avoid 'Choices to Avoid' fish such as swordfish, shark, and king mackerel.
Seek Medical Advice: If you suspect mercury poisoning, consult a doctor immediately, as treatment like chelation therapy may be necessary.

The Silent Accumulation of Methylmercury in Fish

Methylmercury is the primary form of mercury that builds up in fish, and it is a potent neurotoxin. The journey of mercury into your seafood starts with industrial pollution and natural sources that release elemental mercury into the environment. Bacteria in water and soil then convert this mercury into its more dangerous, organic form: methylmercury. This compound is then absorbed by small organisms, which are in turn eaten by larger fish. As you move up the food chain, the concentration of methylmercury increases in a process known as bioaccumulation. Larger, predatory fish like shark, swordfish, and certain types of tuna accumulate the highest levels of mercury because they eat many smaller fish over their longer lifespans.

Immediate and Long-Term Symptoms of Mercury Poisoning

While low-level exposure may not cause noticeable symptoms, high or prolonged consumption of mercury-contaminated fish can lead to a range of serious health issues. Symptoms of methylmercury poisoning can be delayed, sometimes taking weeks or decades to appear, depending on the exposure level. The effects primarily target the central nervous system, and may include:

Neurological problems: Sensations of 'pins and needles' or numbness in the hands, feet, and around the mouth are early indicators.
Impaired coordination: Difficulty with walking, muscle weakness, and tremors (uncontrollable shaking) can develop over time.
Sensory disturbances: Loss of peripheral vision, impairment of speech, and hearing problems are potential effects.
Cognitive and emotional changes: Memory loss, mood swings, irritability, insomnia, and other mental disturbances have been linked to high mercury levels.

Effects on Vulnerable Populations

Unborn infants and young children are particularly susceptible to the effects of methylmercury. Their developing brains and nervous systems are more sensitive to mercury’s neurotoxic effects. Exposure in the womb can impact a child's:

Cognitive thinking
Memory
Attention span
Language and fine motor skills

For this reason, specific guidelines exist for how much fish these populations can safely consume. In severe cases, very high prenatal exposure can lead to profound developmental delays, cerebral palsy, and blindness.

Managing Your Risk: A Guide to Safe Fish Consumption

Balancing the nutritional benefits of fish, such as omega-3 fatty acids, with the risks of mercury exposure is key. The best strategy involves making informed choices about the types and amounts of fish you eat. The FDA and EPA provide guidance on selecting fish with lower mercury levels.

Comparison of Fish by Mercury Level


Best Choices (Lowest Mercury)	Good Choices (More Mercury)	Choices to Avoid (Highest Mercury)
Anchovy	Bluefish	King Mackerel
Catfish	Carp	Marlin
Cod	Halibut	Orange Roughy
Flounder	Mahi-mahi	Shark
Salmon	Snapper	Swordfish
Sardines	Spanish Mackerel	Tilefish (Gulf of Mexico)
Tilapia	Tuna, Albacore (canned/fresh)	Tuna, Bigeye
Shrimp	Tuna, Yellowfin

Here are some tips for safer fish consumption:

Eat a variety: Vary the types of fish you eat to avoid consistently ingesting mercury from a single source.
Choose smaller species: Younger, smaller fish tend to have lower mercury levels as they have had less time to accumulate the neurotoxin.
Follow advisories: Check local advisories for fish caught in specific areas, as contamination levels can vary by location.
Limit high-mercury options: Reserve high-mercury fish for special, infrequent occasions, or avoid them entirely, especially if pregnant or breastfeeding.

What to Do in Case of Mercury Exposure

If you suspect you have been exposed to high levels of mercury from fish or have symptoms of poisoning, it is essential to seek medical attention. A healthcare provider can assess your exposure and determine the best course of action. In severe cases, treatment may involve chelation therapy, where medication is used to bind to heavy metals in the bloodstream and help remove them from the body. Early intervention is crucial for a better prognosis, as the extent of recovery can depend on the severity of exposure and overall health. More information on safe fish consumption can be found on the FDA's official advice page.

Conclusion: Making Informed Choices for Health

Eating fish can be a nutritious part of a balanced diet, offering vital omega-3 fatty acids and other nutrients. However, the potential for mercury contamination requires careful consideration, especially for developing children and fetuses. By understanding which fish are highest in mercury and choosing low-mercury alternatives, you can significantly reduce your risk of mercury poisoning. Making informed choices and following recommended consumption guidelines ensures you and your family can enjoy the health benefits of seafood with minimized risk. Regular monitoring and seeking professional medical advice for any concerns related to mercury exposure are also important steps in maintaining good health.

Frequently Asked Questions

Fish with the lowest mercury levels, categorized as 'Best Choices' by the FDA and EPA, are generally the safest. This list includes salmon, sardines, anchovies, cod, tilapia, and shrimp.

No, cooking does not remove mercury from fish. Mercury is bound to the fish's tissue and is not affected by heat. The only way to reduce exposure is to limit or avoid consumption of high-mercury species.

Early signs of methylmercury poisoning often involve neurological symptoms, such as tingling or numbness in the hands, feet, or around the mouth, and vision changes.

Canned 'light' tuna (skipjack or tongol) typically contains lower mercury levels than canned 'white' or albacore tuna. It is generally considered a 'Best Choice', but consumption guidelines for albacore tuna differ based on age and pregnancy status.

For most healthy adults, 2 to 3 servings (about 8-12 ounces) of low-mercury fish per week is recommended. Vulnerable groups, like pregnant women, have more stringent guidelines to follow.

Yes, chronic, high-level exposure to methylmercury can lead to permanent neurological damage, affecting motor skills, cognition, and sensory functions.

Pregnant women should strictly avoid high-mercury fish and limit low-mercury fish intake to specific amounts recommended by health authorities to protect the developing fetus's brain and nervous system.