Mercury Poisoning From Fish: Is It Really Possible?

It’s pretty much common knowledge that too much fish can result in mercury poisoning. But what is mercury poisoning, and are you really at risk?
Updated 8 December 2022
Mercury Poisoning From Fish: Is It Really Possible?
Sections on this page
  1. Symptoms of Mercury Poisoning
  2. Can You Really Get Mercury Poisoning From Fish?
  3. How Much Fish Can Give You Mercury Poisoning?
  4. Treatment for Mercury Poisoning from Fish
  5. How to Prevent Mercury Poisoning from Fish
  6. Frequently Asked Questions

Mercury poisoning usually happens when you ingest too much natural mercury (specifically, methylmercury, which is found in fish), causing various health issues. Although mercury is not found in many different foods, it is common to get mercury poisoning from fish. 

It has also been suggested that mercury poisoning can also be caused by various skin products containing mercury, such as anti-aging creams. 

Symptoms of Mercury Poisoning

According to the Agency for Toxic Substances and Disease Registry (ATSDR), mercury poisoning can lead to:

  • Permanent brain damage
  • Permanent kidney damage
  • Personality changes (e.g., irritability, increased shyness)
  • Tremors
  • Vision problems
  • Hearing problems
  • Muscle weakness and coordination issues
  • Loss of sensation in various parts of the body
  • Loss of memory
  • Depression
  • Anxiety
  • Troubles breathing

It’s common for mercury poisoning to result from eating fish and shellfish with high levels of mercury over time vs. happening in a short amount of time. 

Signs of Mercury Poisoning in Children 

Mercury poisoning is especially dangerous for young children, including unborn babies. If this group is exposed to too much mercury, they may have problems with:

  • Speech and language development
  • Cognition
  • The development of their fine motor skills
  • Visual-spatial awareness

Can You Really Get Mercury Poisoning From Fish?

Mercury is both naturally occurring and a result of human pollution. As a result, it can be found almost anywhere but is most common in areas of high pollution. The mercury in the air is not what we’re talking about here, but it does play a part in mercury poisoning. 

The mercury found in the air eventually falls, making its way into our oceans, rivers, and lakes. From there, organisms living in these bodies of water end up ingesting the mercury. Larger sea creatures then eat these organisms (and the mercury within them), and we continue up the food chain. 

As each organism gets eaten, more mercury is contained, leaving the larger predators like tuna and sharks with the highest mercury concentrations. 

So, yes. You really can get mercury poisoning from overeating fish, but it does depend on the type of fish and how much you consume.

How Much Fish Can Give You Mercury Poisoning?

We’re not saying you need to give up fish entirely here. On the contrary, fish and other types of seafood contain beneficial omega-3 fatty acids, vitamins, and other nutrients, so you shouldn’t avoid them altogether in fear of mercury poisoning.

You should, however, limit your intake to eating seafood that is high in mercury to only one or two meals per week. If you want to eat seafood more regularly, choose those containing little or no mercury. 

To get technical, you should keep your mercury levels to 1 part per million (ppm) per week. See the table below for a guide on the amount of mercury found in different types of fish. 

Mercury Toxicity in Commonly Eaten Seafood 

Seafood Average Mercury Level (ppm) Max. Servings Per Week
Swordfish 0.995 1
Mackerel (king) 0.730 1
Grouper 0.448 1
Tuna 0.391 1-2
Tuna (albacore) 0.358 1-2
Tuna (yellowfin) 0.354 1-2
Croaker white 0.287 2-3
Halibut 0.241 2-3
Snapper 0.166 3-4
Bass 0.152 3-4
Canned Tuna 0.128 3-4
Cod 0.111 3-4
Lobster 0.107 3-4
Whitefish 0.089 n/a
Herring 0.084 n/a
Trout 0.071 n/a
Crab 0.065 n/a
Catfish 0.025 n/a
Squid 0.023 n/a
Salmon 0.022 n/a
Sardine 0.013 n/a
Tilapia 0.013 n/a
Oyster 0.012 n/a
Clam 0.009 n/a
Shrimp 0.009 n/a
Scallop 0.003 n/a

Treatment for Mercury Poisoning from Fish

If you end up with mercury poisoning from consuming too much seafood, your doctor may prescribe medication to help you rid your body of the mercury. Alternatively, the only other “cure” is to stop eating seafood and wait to recover naturally. Drinking water and eating more fiber may help you to recover faster.

If your poisoning is so severe that it results in long-term damage, you’ll need specific medical care to treat those conditions. 

Since there’s essentially no treatment other than to detox your body from the mercury, the best thing to do is prevent mercury poisoning from occurring in the first place. 

Expectant Mothers Should Avoid Mercury Altogether

If you’re pregnant, the safest thing to do is avoid seafood with high levels of mercury altogether. This will keep your fetus safe from any potential development issues caused by mercury. 

How to Prevent Mercury Poisoning from Fish

  • Stay away from seafood containing high levels of mercury. 
  • Eat foods high in mercury only once or twice a week. 
  • Limit your consumption of large fish (these contain higher levels of mercury). 

Frequently Asked Questions

How much salmon causes mercury poisoning?

Salmon is relatively low in mercury compared to other types of fish, so most people can eat 2-3 servings of salmon a week without experiencing harmful effects. 

How much tuna causes mercury poisoning?

There are varying ranges of mercury in different types of tuna, so there isn’t a straight answer for this. Large tuna, such as fresh bluefin or yellowfin tuna contain very high levels of mercury, so it’s generally recommended to only have one serving a week (or to avoid them completely if you’re pregnant). 

Tuna with lower levels of mercury, including canned tuna can be eaten 3-4 times a week for most people. 

Can you die from mercury poisoning from fish?

It’s rare for mercury poisoning from consuming fish to lead to death. However, it can result in fetal death if pregnant women eat too much fish with high levels of mercury. 

When death is a result of mercury poisoning, it’s usually due to inhaling mercury vapor. 

Can cats get mercury poisoning?

Yes, cats can get mercury poisoning from overeating fish. The best practice is to limit fish products to 10% of your cat’s diet to avoid mercury poisoning.

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