What Causes Urine to Smell Like Fish and How Is This Treated?

Medically reviewed by Alana Biggers, MD on December 8, 2017Written by Ana Gotter on December 8, 2017

Is this cause for concern?

Urine is made up of water and a small concentration of waste products. Urine typically has a subtle odor of its own, but this can change or fluctuate for a number of reasons. In some cases, your urine may even take on a fishy smell.

Although this is usually temporary and easily remedied, it can sometimes be a sign of an underlying condition that requires more advanced treatment.

Keep reading to find out what may be behind your symptoms, and what you can do to find relief.

1. Diet and dehydration

Your urine contains some of the chemical compounds found in food you’ve recently consumed. These compounds will carry some of the food’s scent into your urine.

With that in mind, it’s unsurprising that eating fish can cause your urine to have a fishy smell.

Other foods and drinks that can cause this include:

  • caffeine, which can act as a diuretic
  • asparagus, which can release of sulfur in the urine
  • Brussel sprouts and cabbage, which release methyl mercaptan that can cause a strong fish or rancid smell

Dehydration can also cause or aggravate the fishy smell in your urine. When you’re dehydrated, there’s less water to dilute the concentrations of chemicals. This will give your urine a stronger smell.

What you can do

You can avoid foods known to cause fishy-smelling urine, but this can be difficult to do. Instead, make sure you drink plenty of water — especially when drinking caffeine — to help dilute the scent and stay hydrated.

2. Urinary tract infection (UTI)

A UTI can cause bacteria from the infection to contaminate the urine, resulting in a distinct fishy smell. UTIs are more common in women than men.

Other symptoms include:

  • urine that is cloudy or bloody
  • pain or burning during urination
  • feeling the need to urinate urgently or frequently
  • lower abdominal or back pain
  • mild fever

What you can do

If your symptoms haven’t disappeared within 24 hours, see your doctor. They’ll prescribe antibiotics to help eradicate the infection before it spreads to the kidneys.

3. Bacterial vaginosis

Bacterial vaginosis occurs when there is too much “bad” bacteria in the vagina, disrupting the balance of “good” and “bad” bacteria. This can cause a grayish, fishy-smelling vaginal discharge that may be noticeable when urinating.

Some women with bacterial vaginosis won’t experience any symptoms.

If symptoms are present, they may include:

  • discharge that is thin or watery
  • pain during intercourse
  • painful urination
  • light vaginal bleeding

What you can do

Sometimes bacterial vaginosis will go away on its own. If your symptoms persist for a week or more, see your doctor. Your doctor can treat it with antibiotics, though it may return after treatment is over.

4. Trimethylaminuria

Trimethylaminuria is a rare metabolic disorder that occurs when the body is unable to break down certain compounds properly. This includes fishy-smelling trimethylamine.

Trimethylamine is produced in the intestines after consuming certain types of food that are high in protein. With trimethylaminuria, trimethylamine is released into the urine instead of being broken down.

What you can do

Trimethylaminuria is inherited, and there is no cure. However, you can reduce your symptoms by avoiding foods that trigger symptoms.

These include:

  • eggs
  • legumes
  • liver
  • fish
  • milk that comes from wheat-fed cows
  • bananas
  • soy
  • different types of seeds

5. Prostatitis

Prostatitis is an acute inflammation of the prostate gland in men. It’s caused by a bacterial infection. It can progress quickly. The bacteria in the urine can cause it to smell like fish.

Other symptoms may include:

  • fever
  • chills
  • body aches
  • burning during urination
  • lower back pain
  • blood in the urine
  • cloudy urine
  • pain in the genital region, including the penis, testicles, and perineum
  • difficulty emptying the bladder completely

What you can do

If you suspect prostatitis, see your doctor. Your doctor will prescribe you antibiotics to treat the infection.

While you’re waiting for the antibiotics to work, your doctor may prescribe you alpha blockers. These relax the bladder neck and reduce painful urination. Anti-inflammatory drugs —including over-the-counter options like ibuprofen (Advil) — can also be effective.

6. Kidney stones

Kidney stones that are moving into or from the kidneys can cause an infection somewhere in the urinary tract. This infection will affect the urine, and can cause urine that smells like fish. It may also cause blood in the urine or cloudy urine.

Kidney stones can cause severe pain that radiates from the side and back down towards the groin. This pain will come in waves and fluctuate in intensity. It may cause vomiting and severe nausea.

If an infection is present, you may also have a fever and chills.

What you can do

Some kidney stones will pass on their own, but if you’re experiencing severe pain you should see your doctor.

Your doctor can prescribe pain medication to make your symptoms more bearable. They can also prescribe an alpha blocker to relax the bladder and make it easier for the stone to pass.

If the stone is larger and at risk to become stuck in the urinary tract, your doctor may do surgery to remove it.

7. Liver problems

Although liver problems usually don’t cause urine that smells like fish, it’s possible.

This is especially true of liver failure. This occurs when the liver isn’t functioning properly, and is unable to process toxins as it should. These toxins are then released in the urine, causing the strong smell.

If liver problems are causing fish-smelling urine, you’re likely to notice other symptoms, too. This includes:

  • thicker, darker urine
  • urination that becomes more difficult, partially because of the thicker urine
  • jaundice
  • nausea
  • loss of appetite
  • diarrhea
  • fatigue

What you can do

If you’re experiencing symptoms like these, see your doctor. They may be a sign of an underlying liver problem or a complication of an already-diagnosed condition.

Your individual treatment plan will depend on the diagnosis. Some liver problems will be treated with lifestyle changes, including a modified diet and potentially losing weight. Others may require treatment, including dialysis, or surgery.

8. Cystitis

Cystitis refers to inflammation of the bladder. It’s often caused by a bacterial infection, such as a UTI. The bacteria from the infection can result in a strong fish smell in the urine.

Other symptoms include:

  • a strong, persistent urge to urinate
  • passing small amounts of urine frequently
  • burning during urination
  • cloudy, bloody, or strong-smelling urine
  • pelvic discomfort
  • pressure in the lower abdomen
  • fever

What you can do

If you suspect you have cystitis, see your doctor. They will likely prescribe you antibiotics to get rid of the infection before it spreads to the kidneys. You can use a heating pad to relieve discomfort. Drinking plenty of water can help flush the infection from your system.

9. Phenylketonuria

Phenylketonuria is an uncommon inherited disorder that raises the number of phenylalanine in the blood. This can cause a build-up of the substance in the body, as well as a high concentration of phenylalanine in the urine. This can cause a fishy odor.

Phenylketonuria usually affects infants. If the gene has been passed on to your child, they will start to display signs of phenylketonuria within the first several months of being born.

Other symptoms include:

  • delayed mental and social skills
  • hyperactivity
  • head size that’s much smaller than usual
  • skin rashes
  • tremors
  • seizures
  • jerking movement of the arms and legs

What you can do

Phenylketonuria can’t be cured, but treatment can be highly effective at managing symptoms. It’s essential to follow a diet low in phenylalanine.

This means avoiding foods containing the substance, such as:

  • milk
  • cheese
  • some artificial sweeteners
  • fish
  • chicken
  • eggs
  • beans

10. Trichomoniasis

Trichomoniasis is a sexually transmitted infection (STI) caused by a protozoan parasite.

Some people with trichomoniasis won’t experience any symptoms. In some women, however, the infection causes vaginal discharge that has a strong fish-like odor. This discharge may be clear, white, yellow, or greenish.

Other symptoms include:

  • genital itching
  • burning near the genitals
  • redness or soreness of the genitals
  • pain or discomfort when urinating

What you can do

If you suspect trichomoniasis, see your doctor. They’ll prescribe oral antibiotics to clear the infection. To prevent reinfection, wait 7 to 10 days after both you and your partner have finished treatment to resume sexual activity.

When to see your doctor

If your urine has started to smell like fish and there isn’t an obvious reason why — like diet or dehydration — make an appointment to see your doctor within the next couple of days.

You should see your doctor as soon as possible if you’re experiencing:

  • painful urination
  • blood in the urine
  • fever

You should seek emergency medical attention if you’re experiencing:

  • severe pain while urinating
  • nausea
  • vomiting
  • severe back or abdominal pain
  • fever of 103°F (39.4°C) or higher

In these cases, you may have a kidney stone, or an infection that is spreading to your kidneys.

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