3 Fish Parts You Should Never Eat: One May Contain Toxins, Another May Increase the Risk of Kidney Damage

Fish is widely recognized as a nutritious food. It provides high-quality protein, omega-3 fatty acids, vitamin D, selenium, iodine, and other nutrients that can support heart, brain, and overall health.

But there is an important detail that is sometimes overlooked: not every part of a fish is equally suitable for eating.

Certain organs can accumulate environmental contaminants, while some preparation methods can create additional food-safety concerns. Viral posts often describe these parts as foods you should “never eat,” but the real issue is more nuanced. The risk depends on the fish species, where it was caught or farmed, the size and age of the fish, and how frequently a person consumes it.

Here are three fish parts that deserve particular caution.

1. The Fish Liver

The liver performs an important detoxification and storage role in fish. Because of this, it can accumulate certain substances from the environment, including fat-soluble contaminants.

One well-known example is vitamin A.

Some fish livers can contain extremely high concentrations of preformed vitamin A. Eating unusually large quantities can potentially lead to vitamin A toxicity, which may cause symptoms such as nausea, headache, dizziness, skin changes, and—in severe cases—more serious health problems.

The liver can also accumulate environmental contaminants depending on the species and habitat.

This does not mean that every fish liver is poisonous. Fish liver has been consumed traditionally in several cultures, and some fish-liver products are commercially regulated.

The concern is primarily about which species you are eating, how much you consume, and how often you consume it.

People should be particularly cautious about consuming the organs of large, long-lived wild fish from waters where contamination is a known concern.

2. Fish Gallbladder

The gallbladder is another organ that is generally not considered an appropriate food.

It stores bile, a digestive fluid produced by the liver. Accidentally rupturing the gallbladder while preparing fish can release bile into the surrounding tissue and create an extremely bitter taste.

More importantly, consuming gallbladder contents is not a safe practice.

There have been documented cases of poisoning associated with ingestion of raw fish gallbladder, particularly involving certain freshwater fish. Some cases have resulted in severe kidney and liver injury.

This is where the kidney-damage warning commonly seen in viral social-media posts comes from.

The danger isn't simply that “fish is bad for the kidneys.” Rather, certain fish species contain compounds that can cause serious toxicity when their gallbladders are consumed.

Symptoms of serious poisoning may include:

• Nausea and vomiting
• Abdominal discomfort
• Weakness
• Reduced urine output
• Swelling
• Abnormal kidney function
• Acute kidney injury

In severe cases, hospitalization and intensive medical treatment may be required.

For this reason, eating fish gallbladders—especially raw or deliberately consumed as a traditional remedy—is something to avoid.

3. Fish Intestines and Digestive Organs

The digestive tract is another part that requires careful handling.

Fish intestines can contain microorganisms and parasites because they are directly involved in digestion and are exposed to the contents of the gastrointestinal tract.

That doesn't mean eating fish automatically exposes you to dangerous parasites. Proper cleaning and thorough cooking substantially reduce many foodborne risks.

The bigger concern comes when digestive organs are eaten raw, undercooked, improperly cleaned, or prepared using unsafe practices.

Some raw or inadequately cooked freshwater fish can transmit parasites capable of causing human disease.

Depending on the parasite, infection may affect the intestines, liver, bile ducts, or other organs.

Symptoms can include abdominal pain, nausea, diarrhea, fever, fatigue, or other digestive problems.

That's why fish intended for consumption should be handled carefully and cooked according to appropriate food-safety guidance.

What About Fish Skin, Eyes, and Heads?

This is where viral posts can become misleading.

Not every unusual fish part is automatically dangerous.

In many cultures, fish skin, cheeks, heads, and other parts are routinely eaten. Some are excellent sources of protein and other nutrients.

The safety question depends on the species and preparation.

For example, some contaminants such as mercury are distributed throughout fish tissue rather than being limited to one specific organ. Large predatory fish can accumulate more mercury because they consume smaller contaminated fish over their lifetime.

Therefore, simply removing one organ doesn't necessarily eliminate every contaminant concern.

Pregnant people, breastfeeding individuals, young children, and people who eat fish frequently should pay particular attention to official fish-consumption advisories.

Why Large Fish Can Require More Caution

A useful rule when thinking about environmental contaminants is bioaccumulation.

Some pollutants can build up in an individual fish over time.

There is also biomagnification, where concentrations of certain contaminants become higher as you move up the aquatic food chain.

That means large predatory fish can sometimes contain higher levels of contaminants than smaller fish.

Examples of species that may require greater attention to mercury exposure include certain types of shark, swordfish, king mackerel, and bigeye tuna.

This is why health authorities generally recommend eating a variety of fish rather than relying heavily on one species.

How to Eat Fish More Safely

You don't need to stop eating fish.

For most people, fish can be an excellent part of a balanced diet.

A few basic precautions can make a major difference:

Choose a variety of fish.
Rotating species can reduce repeated exposure to contaminants that may be concentrated in particular fish.

Follow local fishing advisories.
If you're eating fish caught from a river, lake, or coastal area, check whether authorities have issued warnings about mercury, PCBs, or other contaminants.

Avoid consuming fish gallbladders.
There is no nutritional reason to deliberately eat this organ, and certain fish gallbladder poisonings can cause severe kidney injury.

Clean fish properly.
Remove the digestive tract and other organs carefully, particularly when preparing whole fish.

Cook fish thoroughly when appropriate.
Cooking reduces the risk from many parasites and foodborne pathogens, although it does not eliminate every environmental contaminant.

Be especially careful with raw freshwater fish.
Some parasites are associated with raw or undercooked freshwater fish.

The Bottom Line

The viral claim that there are “three fish parts you should never eat” is too broad to apply to every fish species worldwide.

However, there is a legitimate food-safety lesson behind the headline.

Fish gallbladders should not be deliberately consumed, because poisoning from certain fish species can cause severe kidney injury.

Fish liver and digestive organs also deserve caution because they can contain concentrated nutrients, environmental contaminants, parasites, or other hazards depending on the species and preparation.

The safest approach isn't to fear fish. It's to understand which species you're eating, which parts you're consuming, where the fish came from, and how it was prepared.

Fish remains an important source of high-quality protein and beneficial nutrients. The goal is simply to enjoy it safely—and to leave questionable organs and risky preparation practices off the menu.