Why Does My Pee Smell Like Fish

Trimethylaminuria, better known as fish odor syndrome, is a rare disorder that causes a person’s bodily emissions to smell like fish. The odor can arise from the saliva, sweat, or urine. A person develops this condition when they are not able to break down TMA.

Why does my urine smell like fish?

The smell of urine often changes based on a person’s diet or fluid intake. However, a strong fishy odor may be the first sign of a severe medical issue.

If fishy-smelling urine is the only symptom, a person may want to wait for a couple of days to see if it clears up. If other symptoms are present and include pain in the lower back or difficulty urinating, a person should contact their doctor.

In this article, we look at the causes, symptoms, and treatments for urine that smells like fish.

Urine sample to determine why urine smells like fish

A fishy smell is uncommon in urine. Many of the causes are not serious, but it can sometimes indicate a severe condition, such as damage to the kidneys or liver.

In many cases, the culprit responsible for the smell of fish is a chemical called trimethylamine oxide. When a fish dies and bacteria begin to decompose the tissue, this chemical is released and converted to trimethylamine (TMA), which causes the fishy odor.

A fishy smell in urine may be caused by the presence of bacteria, TMA, or an interaction between them.

According to a study from 2013 , most healthy people produce chemicals that break down TMA, which stops them from smelling like fish, even when they have eaten fish recently or have a lot of bacteria in their systems.

If a person suspects that any of the following causes are responsible for the fishy smell, it is usually safe to wait a few days and see if the smell clears up without treatment.


Pregnancy can make the urine more concentrated. This can lead to a stronger smell, and it may make a fishy smell more noticeable. See a doctor if the smell does not disappear in a day or two.

Dehydration during pregnancy can make the urine look darker or smell worse. A person who is pregnant and noticing these symptoms should ensure that they are drinking enough water.

Vitamins and supplements

Some of these can make the urine smell fishy, especially supplements of calcium, vitamin B6, and vitamin D. The odor may be more noticeable when a person is dehydrated. If an individual stops taking these supplements and their urine still smells fishy, they should contact a doctor.


Certain foods, including asparagus and fish, can make the urine smell. If foods are responsible, the smell should go away after a few hours.

Fishy-smelling urine may be the first indication of a mild or severe health problem. Some people may have no other symptoms or several. In either case, a person should contact a doctor if they cannot identify the cause of a fishy odor.

The following causes often require medical attention:

Urinary tract infections (UTIs)

A UTI occurs when too much harmful bacteria grow in the urinary tract. This can make the urine smell. In some people, a UTI causes no symptoms. When symptoms are present, they often include:

  • pain when urinating
  • an intense need to urinate
  • frequently needing to urinate, even immediately after using the bathroom
  • blood in the urine

Most UTIs can be treated with antibiotics. If left untreated, a UTI may spread to the kidneys.

Anyone who suspects that they have a UTI should see a doctor.

Bacterial vaginosis (BV)

This bacterial infection in the vagina causes fishy, foul-smelling discharge. While it does not affect the urine, a person may notice the odor while using the bathroom.

The smell and other symptoms may get worse immediately after sex. Women with BV may believe that they have a yeast infection, but the smell is a distinguishing factor. Some other symptoms include:

  • burning in or around the vagina
  • pain during sexual intercourse
  • gray or frothy vaginal discharge

BV is common in sexually active women. Some sexually transmitted infections may also cause an unusual odor, and it is important to see a doctor for testing.

Fish odor syndrome

Trimethylaminuria, better known as fish odor syndrome, is a rare disorder that causes a person’s bodily emissions to smell like fish. The odor can arise from the saliva, sweat, or urine. A person develops this condition when they are not able to break down TMA.

In many cases , the disorder is passed genetically and causes no other symptoms. Less often, a person who has a diet very high in TMA and unusual bacteria in the gut can develop the syndrome.

A person emitting a fishy odor that persists, in spite of good hygiene, should see a doctor. Dietary changes, antibiotics, and nutritional supplements may help.

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Kidney problems

Share on Pinterest Pain in the lower back may be a symptom of a kidney infection.

The kidneys filter the urine, which helps to remove toxins from the body. When the urine smells, it may indicate that the kidneys are not functioning correctly, often due to infections or kidney stones.

Symptoms of a kidney infection may include:

  • difficulty urinating, or painful urination
  • a UTI that gets worse
  • pain in the lower back
  • a high fever
  • blood in the urine

Kidney infections may require hospitalization, though some can be managed at home with antibiotics. Anyone with symptoms of a kidney infection should see a doctor right away.

Kidney stones are mineral deposits that collect in the kidneys. They can be as small as a grain of rice or grow to resemble pebbles and small rocks.

Passing a kidney stone can be painful. Sometimes they become stuck. A person who is first experiencing symptoms, or who notices bleeding when trying to pass a kidney stone, should see a doctor. Drinking plenty of water can help the stone to pass more quickly.


Prostatitis describes swelling and inflammation of the prostate, and it is often the result of an infection. People with prostatitis may notice changes in urination, including a fishy smell.

Symptoms of prostatitis are similar to those of a UTI. People with prostatitis may also experience:

  • pain in the anus, perineum, or scrotum
  • lower back pain
  • chills and body aches
  • a weak urine stream

Treatment depends on the cause of the inflammation. A doctor may prescribe medication, such as antibiotics and pain relievers, or they may recommend surgery. Warm sitz baths can help with managing the pain at home.

Liver failure

Like the kidneys, the liver helps the body to filter out toxins. When the liver is not functioning correctly, it releases more of a substance called bilirubin into the blood. This can pass into the urine, making it smell bad.

Symptoms of liver failure include:

  • unexplained nausea or vomiting
  • loss of appetite
  • yellow skin, nails, or eyes
  • itching
  • retaining fluid
  • swollen ankles
  • exhaustion
  • diarrhea

Some people are more susceptible to liver failure than others. Anyone with one or more of the following conditions should contact a doctor immediately if they suspect that their liver is failing:

  • hepatitis
  • fatty liver disease
  • any autoimmune disease
  • cirrhosis
  • bile duct disease
  • metabolic disorders

Treatment will depend on the extent of the liver failure, but it may include medication, hospitalization, or a liver transplant.

Fishy-smelling urine is not often a medical emergency. However, people who experience pain, a fever, or signs of kidney or liver problems should call a doctor or visit the emergency room.

When no other symptoms are present, the smell may disappear without treatment in a few days. If this does not happen, a person should consult a doctor.

It is easy to overlook urine as an indicator of health, but it can provide important information about how well the body is functioning.

While fishy-smelling urine may be alarming, the causes are usually minor. A doctor can provide a diagnosis and recommend the quickest path to recovery.

A fishy smell in the urine will often go away without treatment in a few days. If the smell does not improve, seek medical attention. Serious conditions can occasionally be responsible for this odor, and prompt treatment can be vital.

Last medically reviewed on April 12, 2018

  • Urinary Tract Infection
  • Nutrition / Diet
  • Pregnancy / Obstetrics
  • Urology / Nephrology
  • Cat 1
  • urinaryhealth

How we reviewed this article:

Medical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

  • Herrine, S. K. (n.d.). Liver failure
  • Imam, T. H. (2016, May). Bacterial urinary tract infections (UTIs)
  • Is fish smelly? (2011, August 24)
  • Kidney stones. (n.d.)
  • McKenzie, A. L., Munoz, C. X., Ellis, L. A., Perrier, E. T., Guelinckx, I., Klein, A., . . . Armstrong, L. E. (2015, November 16). Urine color as an indicator of urine concentration in pregnant and lactating women. European Journal of Nutrition, 56(1), 355–362
  • Messenger, J., Clark, S., Massick, S., & Bechtel, M. (2013, November). A review of trimethylaminuria: (Fish odor syndrome). The Journal of Clinical and Aesthetic Dermatology, 6(11), 45–48
  • Prostatitis: Inflammation of the prostate. (2014, July)
  • Schulz, L., Hoffman, R. J., Pothof, J., & Fox, B. (2016, July). Top ten myths regarding the diagnosis and treatment of urinary tract infections [Abstract]. The Journal of Emergency Medicine, 51(1), 25–30
  • Smelly urine. (2017, October 16)
  • Soper, D. E. (2015, January). Bacterial vaginosis (BV)
  • Symptoms of liver failure. (n.d.)

What the Smell of Your Pee Can Tell You About Your Health

Four cylinder of air freshener in a row.

Urine smells are normally different from person to person, but a few specific smells can tip you off that something’s going on with your health.

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Image Credit: Mihailgrey/iStock/GettyImages

Sometimes it smells like nothing. Other times, like when you wake up in the morning, your pee has that, well, “strong pee smell.” Or it might smell fruity, sour or even fishy. So, what’s going on?

“Urine will have a characteristic odor that may be different in each person,” Piyush Agarwal, MD, professor of surgery and urology and director of the Bladder Cancer Program at The University of Chicago Medicine, tells LIVESTRONG.com.

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But when there’s something funky going on — your urine does not smell “normal” to you — you probably have questions. Before you rely on your pee smell to self-diagnose, though, keep in mind that smells can be up for interpretation. What you’d describe as pee that smells sweet, another person might say smells fruity.

What’s more, while odor is important, it’s often not as telling as other signs, including urine color.

So pay attention to the stink and report any concerns to your doctor, but don’t assume the worst if the aroma you’re producing is a little off.

Now, let’s get on with it. If your urine smells like the following, here’s what may be going on:

1. If Your Urine Smells Like Ammonia.

You may be dehydrated.

Urine is mostly made up of water, with the addition of waste products like urea. If you have foul-smelling or pungent urine that has a strong ammonia scent, then it’s likely you’re dehydrated, leading to more concentrated urine.

Where doctors worry is when you have additional symptoms. For instance, an ammonia smell to your urine along with burning, pain with urination and fever may point to a urinary tract infection (UTI), Dr. Agarwal says.

Fix it:​ Drinking more water will dilute your urine, which will tame the smell. You’ll know you’re properly hydrated if your pee is somewhere between clear and a light yellow color, per the Cleveland Clinic.

If you have additional symptoms, make an appointment with your doctor.

2. If Your Pee Smells Fishy.

You might have an infection.

Trichomoniasis is a sexually transmitted disease (STD) that can affect people of any sex. People assigned male at birth often have no symptoms, but those assigned female can have a fishy-smelling vaginal discharge. While discharge is distinctly different than urine, that may be the scent you’re smelling when in the bathroom.

Along with the odor, discharge may be greenish-yellow, and you may experience vaginal irritation, notes the Centers for Disease Control and Prevention.

Fix it:​ This infection is cured with a single dose of antibiotics.

3. If You Have Sweet-Smelling Urine.

It might be an infection, or it could be diabetes.

Some patients who have UTIs actually describe the smell of their urine as sweet, Dr. Agarwal says.

More commonly, this might be a sign of diabetes. If you have uncontrolled diabetes, sugar is being eliminated in your urine, which can add a sweet smell.

“This would be accompanied by going to the bathroom more frequently and an increased urge to go,” Dr. Agarwal says.

4. If Your Pee Smells Strong.

It could be dehydration, or maybe it’s the supplement you’re taking.

As we noted before, your pee is more concentrated when you’re dehydrated, so it has that strong pee smell.

Another cause behind that smell, though, can be B-6 vitamins, according to the Cleveland Clinic. The vitamin is water-soluble, meaning it is eliminated in the urine. Check your supplements and multivitamin: How much B6 do they contain?

Fix it:​ Drink more water if you’re dehydrated. If it’s your supplement, consider switching to a vitamin with lower levels of B-6.

5. If Your Urine Smells Really Bad.

You may have a structural problem.

Sometimes the GI tract can form an abnormal connection to the urinary tract, called a fistula. “That causes some stool contents to be eliminated in the urine,” Dr. Agarwal says.

Your urine may take on a really nasty smell because of these fecal particles, may have a brownish color and you may hear air passing through your urethra as you’re peeing. However, foul-smelling urine might be the first sign, he says.

Fix it:​ This warrants a call to your doctor, who will look for the underlying cause of the fistula (such as colon cancer or an inflammatory disorder) and recommend surgery, according to the Urology Care Foundation.

6. If Your Pee Smells Like Sulfur.

Did you just eat asparagus, perhaps?

“Foods will change the smell of urine,” Dr. Agarwal says. Asparagus is by far the most famous for doing this, and that’s because sulfur byproducts of the veggie are being eliminated in the urine.

Fun fact: Lots of people can’t smell “asparagus pee” because of certain genetic variants that make them unable to detect this odor. In one study published in ​The BMJ​ in 2016, about 60 percent of people claimed they didn’t have smelly pee after eating asparagus. (They really did, but their noses were none the wiser.)

Other foods that are known to change your urine odor include garlic, salmon, Brussels sprouts and curries, Dr. Agarwal says.

Fix it:​ Not much you can do here, really — the smell will go away on its own.

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Alex Koliada, PhD

Alex Koliada, PhD

Alex Koliada, PhD, is a well-known doctor. He is famous for his studies of ageing, genetics and other medical conditions. He works at the Institute of Food Biotechnology and Genomics NAS of Ukraine. His scientific researches are printed by the most reputable international magazines. Some of his works are: Differences in the gut Firmicutes to Bacteroidetes ratio across age groups in healthy Ukrainian population [BiomedCentral.com]; Mating status affects Drosophila lifespan, metabolism and antioxidant system [Science Direct]; Anise Hyssop Agastache foeniculum Increases Lifespan, Stress Resistance, and Metabolism by Affecting Free Radical Processes in Drosophila [Frontiersin].
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