Why Your Poop Smells Like Fish: Causes & How to Fix

Key takeaways:

• Characteristics of your poop, including the consistency, color, volume, and smell, provide clues about the health of your gut and gastrointestinal tract.
• Irritable bowel syndrome, food sensitivities, malabsorption, and infections are a few common causes of fishy-smelling poop.
• Other symptoms that accompany your fishy-smelling poop may suggest a more serious condition that requires further evaluation.

While poop may not have a pleasant smell at its baseline, sudden changes to your poop can be frustrating and concerning. This may be especially true if you notice a strange, fish-like odor. Your poop is an important indicator of the health of your gastrointestinal tract.

Any changes to the consistency, color, volume, and smell of your poop can be reflective of an underlying condition. If your symptoms persist, worsen, or fail to respond to home treatment, you should speak with your doctor to evaluate the underlying cause of your fishy-smelling poop.

Fishy-smelling poop defined

Although going to the bathroom every day may not be something you look forward to, your bowel movements are an important aspect of your health. Because stool is a result of the digestive process, these changes in your stools and associated symptoms may reflect a change in the health of your gut and gastrointestinal tract.

Healthy, normal stool should not cause problems. However, changes like constipation, diarrhea, blood in the stool, or strong and unusual odors might indicate that you’re dealing with a health concern that requires medical care.

Is it normal for your poop to smell like fish?

Stools are not normally a pleasant scent. Even so, they usually do not smell like fish. Still, it’s possible your fishy-smelling stools may be normal. However, other symptoms – including weight loss, blood in your stool, fever, or abdominal pain – may suggest a more serious cause.

If there is a family history of colorectal cancer or irritable bowel disease (IBD), you may be at increased risk of developing a GI-related condition.

Causes of poop that smells like fish

Many things can cause changes in the smell of your stool. Some of these causes are less severe, such as various foods or medications, while others are more severe, such as malabsorptive syndromes or possible infections. Let’s take a closer look at common causes of fish-like odor in poop.

Irritable bowel syndrome (IBS)

Irritable bowel syndrome, also known as IBS, is a common gastrointestinal disorder. IBS can cause multiple GI symptoms, including changes to your stool.

Unlike other causes that are discussed later in this article, IBS is a functional disorder. This means it is not associated with an anatomical or structural, physiological, biochemical, or organic abnormality of your gastrointestinal tract. Even so, given that IBS accounts for 25 to 50% of all referrals to gastroenterologists in the US, its negative impact on patients and the healthcare system is evident.

Most patients with IBS have notable changes to the consistency of their stools. Some people experience constipation, while others experience the opposite and have diarrhea or loose stools. Some patients have episodes where they fluctuate between these two extremes.

Although unusual-smelling stools are not a common symptom in IBS, they are possible in the event of a flare-up, as patients typically experience worsening symptoms during periods of increased stress.

Malabsorptive syndromes

Healthy stools result from your gut’s ability to properly digest and absorb nutrients from the food you eat. Changes in the smell of your stools, including fishy-smelling stools, may reflect changes in your body’s ability to digest and absorb certain foods or groups of food. These conditions are known as malabsorptive syndromes.

One of the most common malabsorptive syndromes is Celiac disease, which affects your body’s ability to digest and absorb gluten-containing foods. Another common malabsorptive disorder is lactose intolerance, which affects your body’s ability to digest and absorb lactose-containing foods, such as dairy products.

Other malabsorptive syndromes can also affect your body’s ability to digest and absorb foods. In addition to fishy-smelling stools or other changes in the smell of your stools, you may experience associated symptoms, like unintentional weight loss, pale, large-volume stools, excessive gas, and hormonal changes.

Infections

Although bacteria are viewed as bad, you have naturally existing bacteria in your gastrointestinal tract that help you digest. Any changes to this natural bacterial environment can affect your digestion and subsequently lead to symptoms, including fishy-smelling stools. Inflammation of the gut, known as gastroenteritis, can reflect an underlying infection.

Numerous bacteria and viruses can cause gastroenteritis (stomach bug or stomach flu). You may experience accompanying symptoms of abdominal pain, nausea, vomiting, and diarrhea in addition to your fishy-smelling stools.

One particular infection that is known to cause changes to the smell of your stool is Giardiasis, a parasitic infection. With more severe infections, you may also notice fevers or bloody stools. You may be at increased risk for these infections if you have recently traveled outside the country, eaten contaminated food or liquids, have a condition that affects your immunity, or have recently been near anyone else with similar symptoms.

Medications, food sensitivities, and other ingestions

Numerous ingestions can also lead to fishy-smelling stools, including medications, food sensitivities, or dietary changes. Some medications, such as antibiotics, diuretics, and diabetes medications, can affect the smell of your stools.

Food sensitivities are not as severe as malabsorptive syndromes. Even if you have previously had no issues with a certain food or group of foods, food sensitivities can develop at any point in your life.

Read our guides on different types of stool and stool colors for more.

Treatment options for poop that smells like fish

Having fishy-smelling stools can be frustrating and concerning. Below are some treatment options you can try at home to help improve your symptoms.

Dietary changes

Dietary changes can drastically affect the quality of your stool. If you notice drastic changes in your stool after eating a specific food or group of foods, try reducing the amount of that food in your diet to see if your symptoms improve.

You can even try a period without that food, but speak with your doctor to see when it may be appropriate to start eating that food again or if you should avoid it altogether.

Stress reduction and other lifestyle modifications

Stress is a natural and important stimulus for the body; however, it can worsen symptoms when not adequately controlled.

By ensuring that you get adequate sleep, hydration, exercise, and take the time to do activities you like, you can help your body more effectively deal with the effects of stress.

Antibiotics and other medications

Your symptoms may result from an infection, which may require a course of antibiotics or other medication that helps clear the infection. Speak with your doctor to see if you need prescription medications to get rid of a possible infection.

When you should see a doctor about poop that smells like fish

Knowing when you should speak with your primary care provider may help prevent any complications from more serious causes.

You should see a doctor if:

• Your symptoms occur more frequently, or you notice increasing stool volumes.
• You notice weight loss or significant changes in appetite.
• You have recently started taking a new medication or had any changes to your current medications.
• You have any of the following features:
  • Symptoms beginning after 50 years of age
  • Pain or diarrhea during the night
  • Persistent fevers greater than 102 degrees Fahrenheit
  • First-degree relative with IBD or colorectal cancer

You should go to the emergency room if:

• You vomit up blood.
• You notice bright red blood in your bowel movements or black, tarry stools.
• You experience chest pain or ongoing palpitations (the sensation of a racing heart) that does not resolve.
• You are unable to keep any food or liquids down.
• You are experiencing significant dizziness or fainting.

Questions to ask your doctor about poop that smells like fish

• What is causing my stool to smell like fish?
• Will blood work, stool studies, or other tests help identify the cause of my symptoms?
• What treatment options or medications may help address my symptoms?
• What steps can I take to avoid fishy-smelling poop in the future?

Frequently asked questions: poop that smells like fish

Here are some frequently asked questions about fishy-smelling poop.

Does having poop that smells like fish a sign of a liver problem?

Not necessarily. However, if you have fishy-smelling stools alongside one or more of the following symptoms, it may be a stronger indication of a liver problem and indicate you should speak to your doctor:

• Jaundice (yellowing of the skin)
• An increase in the size of your belly
• Increased bleeding or bruising
• Increased fluid retention around your stomach

It’s also smart to speak with your provider if you have fishy-smelling poop and have a family history of liver problems.

What if you’re pregnant and your poop smells like fish?

Pregnancy can cause significant hormonal changes, which can affect many things, including the smell of your stools. If you are pregnant, you should speak with your obstetrician about your symptoms to follow up and determine the next steps.

Final thoughts on fishy odors in stool

Fishy-smelling poop is not a fun thing to deal with. Fortunately, many of its causes are easily treatable, whether they require lifestyle changes or medical care. If you have any questions about your symptoms or notice they persist for a long time or worsen despite attempted treatment at home, speak with your primary care provider for further evaluation and guidance.

General Medicine follows a strict editorial process, including using real experts to write our articles, vetted primary sources, fact-checking, a secondary medical review, and updates as necessary. This article was medically reviewed and fact checked by Dr. Poushali Bhattacharjee, MD.

Sources

MedlinePlus. “Irritable Bowel Syndrome.” National Library of Medicine, 5 Apr. 2018, https://medlineplus.gov/irritablebowelsyndrome.html.

MedlinePlus. “Celiac Disease.” National Library of Medicine, 26 Feb. 2024, https://medlineplus.gov/celiacdisease.html.

MedlinePlus. “Lactose Intolerance.” National Library of Medicine, 11 May 2016, https://medlineplus.gov/lactoseintolerance.html.

Everhart, J E, and P F Renault. “Irritable bowel syndrome in office-based practice in the United States.” Gastroenterology vol. 100,4 (1991): 998-1005. doi:10.1016/0016-5085(91)90275-p, https://pubmed.ncbi.nlm.nih.gov/2001837/.

Longstreth, George F, et al. “Functional bowel disorders.” Gastroenterology vol. 130,5 (2006): 1480-91. doi:10.1053/j.gastro.2005.11.061, https://pubmed.ncbi.nlm.nih.gov/16678561/.