Fishy-Smelling Urine: The 14 Most Likely Causes


Are you wondering “why does my pee smell like fish?” We can help you figure out what’s causing your fishy-smelling urine, how to address it, and if you need to go to the doctor. If your pee smells fishy, keep reading.


Help! My Urine Smells Fishy

It can be pretty alarming to have fishy-smelling urine. But is it necessarily a major health issue?

If your urine smells fishy, there are a number of possible causes. The cause could be as benign and common as slight dehydration or as rare as trimethylaminuria.

In the next few sections, we’ll address all the potential causes of a fishy urine smell. First we’ll go over some common and harmless causes. Then we’ll discuss some common causes that require medical attention of some kind. Finally, we’ll wrap up with the most rare and unusual causes of fishy-smelling pee.


Not what you want to smell when you pee.


Fishy-Smelling Urine: Common, Benign Causes

These common causes of fishy-smelling urine are easily remedied at home and don’t typically require medical intervention.


Minor Dehydration

When you’re somewhat dehydrated, your urine becomes more concentrated. This means that the ammonia smell of the compounds in your urine will become stronger. Some people experience this smell as “fishy.”

(Major dehydration, on the other hand, often leads you to pretty much stop urinating).


Other Symptoms

In addition to being smelly, your urine will probably be darker in color than usual and you will produce less of it. You’ll also be thirsty!

You may also experience dry mouth and dry skin, headache and/or dizziness, and fatigue/sleepiness.



A medical professional can usually diagnose dehydration by analyzing a urine sample. However, for minor dehydration, this is typically not necessary. If you suspect you’re a little dehydrated, you can just drink some water and see if you feel better!



Minor dehydration can be treated by drinking more water or electrolyte-rich fluids like Gatorade or Pedialyte. More severe dehydration may require IV administration. The smell in your urine should go away as soon as you’re re-hydrated and your urine becomes more dilute.


Drink more water! Fancy spigots not necessary.


Alcohol or Caffeine

Alcohol and caffeine are both diuretics. This means that they make you pee more. If you aren’t replenishing your body’s water supply as you drink alcohol or caffeine, you will, in simple terms, pee out a lot of your excess body water. Over the next few hours, your urine will become more concentrated with uric acid and other compounds, which will make the smell stronger. This might be a fishy urine smell or even a coffee-like smell for caffeinated beverages.


Other Symptoms

You’re essentially becoming dehydrated when this happens, so you’ll likely notice some of the other symptoms of dehydration, like thirst, headache, dry mouth, and nausea.

If you’re drinking alcohol, you will probably also experience some of the effects of intoxication, like flushed skin, relaxation, reduced inhibitions, sleepiness, and slowed reactions and reflexes.

If you’re drinking coffee, you’ll probably experience some other effects of caffeine, like increased energy and alertness and increased bowel activity. Higher doses may lead to anxiety and a jittery feeling.



If you only notice the fishy-smelling urine after you consume alcohol or coffee, that’s probably the culprit. There’s nothing to worry about if you take steps to address the issue (like drinking more water with your coffee) and the smell goes away.



You could cut down on your alcohol or caffeine intake. However, making an effort to drink more water when you consume alcohol or caffeine should also help address the smell problem as it will make your urine more dilute.


Weird pee smells? Maybe cut back on your coffee.


Your Diet

Eating certain foods (including salmon and foods high in B6, like asparagus, garlic, and beets) can all make your pee smell a little strange, which might smell fishy to you. So if you’re wondering “why does my urine smell fishy after eating fish?” it’s because your urine often ends up having some of the same compounds that make the fish smell like fish in the first place. This is especially true if you are dehydrated and your urine is pretty concentrated.


Other Symptoms

You shouldn’t experience any other notable symptoms if your urine smells fishy because of food. However, some of these foods might also cause some gassiness or bad breath (garlic is a notable breath offender).



You don’t necessarily need an official diagnosis for this. If you only notice the fishy-smelling urine after you eat a particular food, and you don’t have other bothersome symptoms, the food is the likely culprit.



You don’t need treatment because this isn’t a health issue. However, if the odor bothers you, you can cut the offending food(s) out of your diet.


Beware the dreaded asparagus pee!


Fishy-Smelling Urine: Common Causes That Need Medical Attention

These potential causes of fishy-smelling pee may require a consultation with a physician or other medical professional to resolve.


Supplements and Medications

Certain supplements and medications, like vitamin B6 or fish oil, can cause fishy-smelling urine.


Other Symptoms

You may have other symptoms if your supplement or medication has other side effects.



If the strange smell dates to around the same time that you started taking the medication or supplement, it’s probably the culprit. If it’s a prescription medication, you can consult with your prescribing physician as to whether your medication could be causing your symptoms. Otherwise, consult with your primary care physician.



You can discuss with your doctor whether it’s worth it to stay on the medication or supplement, if you need to adjust your dose, or if you should switch to something else.


Fish oil? Could mean fish pee.


Cystitis/Urinary Tract Infection

An inflamed bladder (cystitis), most commonly caused by a bacterial infection or urinary tract infection, can cause unusually strong-smelling urine or urine that smells fishy.


Other Symptoms

Frequent urge to urinate, burning sensation with urination, feeling unable to empty the bladder, cloudy or bloody urine, pain during sex, pain or pressure in the abdomen or pelvis, and a low-grade fever.



Cystitis is diagnosed through a combination of urine analysis and discussion of your symptoms. In some cases, bladder imaging may be necessary.



Cystitis caused by a bacterial infection can be treated with antibiotics. Other forms of cystitis primarily focus on avoiding triggers and managing symptoms. When the infection clears or the inflammation lowers, your pee should go back to normal.


An inflamed bladder can make your pee smell strange.


Bacterial Vaginosis

Bacterial vaginosis is a condition in which there is an imbalance of the good and bad bacteria in the vagina. Because BV can cause a fishy-smelling discharge or smell to the vagina, women with BV may think that their urine smells fishy.


Other Symptoms

The main symptom of BV is a liquidy, gray or whitish discharge that smells fishy. You may also experience itching or burning in the vagina, a fishy odor after sex or during menstruation, and burning during urination.



BV is diagnosed primarily through testing vaginal secretions. Your doctor may also perform a pelvic exam or test your vaginal PH.



BV is typically treated with antibiotics. BV recurs in many women; to help avoid a recurrence, you can use condoms and limit your number of sexual partners. Additionally, avoid practices like douching or cleaning the vagina with soaps or washes, which can upset the balance of bacteria in the vaginal canal.


Gotta keep the bacterial balance.



Certain sexually transmitted infections (especially chlamydia, trichomoniasis, and gonorrhea) can cause a smelly discharge from the genitals. This may be especially noticeable for women. The smell of the discharge may also make it seem like you have fishy-smelling urine.


Other Symptoms

Other common STI symptoms include burning with urination, painful intercourse, and itching around the genital area. Women may have abnormal bleeding and abdominal pain. Men may have pain or swelling in the testicles.



STIs are typically diagnosed with a swab of the genital area or a urine sample.



Chlamydia, gonorrhea, and trichomoniasis can be treated with a course of antibiotics. When the infection clears, your fishy urine smell should go away. However, for chlamydia and gonorrhea, your sexual partner(s) should also be tested and treated with antibiotics so that they do not simply pass the infection (and the fishy-smelling urine) back to you.


Larry the lizard says, “practice safe sex!”


Prostate Infection/Prostatitis

An infection or inflammation of the prostate gland can cause foul-smelling or fishy-smelling urine, especially if it’s caused by a bacterial infection.


Other Symptoms

Difficulty urinating and/or fully emptying the bladder, frequent urge to urinate, painful or burning urination, weak urine stream, cloudy or bloody urine, pain after ejaculation, pain in the lower back, penis, testicles, and/or perineum;  fever, chills, and aches (if caused by a bacterial infection).



Prostatitis may be diagnosed through a combination of tests, including urine analysis, blood tests, imaging, and a digital rectal exam (to feel if the prostate is swollen or tender).



Treatment is different depending on what is causing your prostatitis. Bacterial prostatitis is treated with antibiotics. Other kinds of prostatitis are typically treated with medication to manage symptoms.


Gotta soothe that angry prostate.



Pregnancy isn’t exactly a medical problem in that it’s not an illness per se, but it does require the care of a physician! Two things happen during early pregnancy that can cause you to wonder why your pee smells like fish. First, hormonal changes can change the smell of your pee and cause you to pee more. Both of these things can lend a more pungent aroma to your urine. Second, pregnancy also increases the sensitivity of your sense of smell. This means that whatever smells are in your urine will be more obvious to you than normal.


Other Symptoms

Other symptoms of early pregnancy include a missed period, very light spotting, sore breasts and back, nausea, fatigue, mood swings, bloating, mild abdominal cramping, constipation, headaches, lightheadedness or dizziness, shortness of breath, intense food cravings or distaste for certain foods, and elevated basal body temperature.



If you aren’t sure if you’re pregnant, taking a pregnancy test will shed some light. A doctor can make a final determination if you get mixed results.



Drinking more water can help dilute the fishy-smelling pee, but nothing can really done about the increased sensitivity of your nose! Rest assured, however, that slightly fishy-smelling urine during pregnancy is normal.


Baby on board; fishy pee optional.


Kidney Stones

Kidney stones are small, hard crystalline deposits that form anywhere in the urinary tract (usually the kidneys) when minerals and salts stick together. This typically occurs when urine is not particularly dilute, so there is a high concentration of minerals and salts in the urine. The presence of kidney stones in the urinary tract can cause a strange or fishy urine smell.


Other Symptoms

The main symptom of a kidney stone is intense pain in the urinary tract, often when the stone passes from the kidney into one of the ureters (the tubes that connect the kidneys to the bladder). The pain will typically be localized to one side (at least initially) beneath the ribs. The pain may change in character and location as the kidney stone moves: it may radiate, come in waves, and/or feel sharp or stabbing. You may also notice pain with urination, cloudy or bloody urine, a frequent need to urinate, urinating only small amounts, nausea/vomiting, and a fever (if the kidney stone is coupled with an infection).



The pain of a kidney stone usually sends people to the doctor (or even the ER). There, you will likely undergo urine testing, blood testing, and diagnostic imaging to see if you have a kidney stone. Because kidney stones have a variety of potential causes, including metabolic disorders, you may be asked to catch your kidney stone by urinating through a strainer so that it can be analyzed.



You can aid the passing of smaller stones by drinking lots of water and taking painkillers. Your doctor may also prescribe medication to relax the ureters. Larger stones may require a medical procedure to break them up. This could be as noninvasive as sound wave therapy or as invasive as surgery.


Pass that through my bladder? Yeouch!


Fishy-Smelling Urine: Unusual Causes

These are the most unlikely (but still possible) culprits if your urine smells fishy.


Liver Disease

Liver disease can cause abnormally high levels of bilirubin (a component of liver bile) and protein to build up in the urine, which can cause musty or fishy-smelling urine.

Other Symptoms

Urine will probably also be a dark, almost brown color. Other symptoms of liver disease include yellowish eyes and skin (jaundice), swelling in abdomen, legs, and/or ankles, unusual stool color, diarrhea, nausea/vomiting/loss of appetite, weight loss, fatigue, disorientation and confusion, abdominal pain, bad breath, itchy skin, and easy bruising.



Liver disease is typically diagnosed through a combination of blood tests, imaging like MRIs and CT scans, and, if necessary, a tissue biopsy. The earlier your liver disease is diagnosed, the better your prognosis; if you have brown urine for more than several days running, make a doctor’s appointment.



There are different kinds of treatment depending on what kind of liver disease you have. You may need to make lifestyle adjustments and/or take medications. More severe issues may require surgery or even a liver transplant.


Pee this color? Get your liver checked out.



Trimethylaminuria (also called TMAU or fish odor syndrome) is a rare metabolic disorder. People with trimethylaminuria can’t break down the compound trimethylamine in their bodies because they have a defect in the enzyme that would normally break the compound down. Trimethylamine is very stinky and has a rotting fish smell. As trimethylamine from food builds up in the body, people with fish odor syndrome will start to excrete the compound in their urine, breath, and sweat. This means that not only will they have fishy-smelling urine, but also fishy-smelling sweat and breath.


Other Symptoms

As described above, other than fishy-smelling urine, people with fish odor syndrome will also have fishy sweat and breath, leading to a general fishy odor. The level of odor varies over time with factors like age, hormone levels, diet, and stress levels. There are not really any other trimethylaminuria symptoms.



Fish odor syndrome is diagnosed through urine tests or blood tests.



Trimethylaminuria has no long-term physiological complications. However, the fishy smell can cause isolation, anxiety, and depression in people with trimethylaminuria.

There is no trimethylaminuria cure, but there are several trimethylaminuria treatment modalities that help reduce the smell. Having a restricted trimethylaminuria diet that avoids the odor-producing foods (like red meat, beans and legumes, egg yolks, and fish) can help, as can taking low-dose antibiotics to reduce gut bacteria. Some studies have suggested that supplementation with activated charcoal and copper chlorophyllin may help break down trimethylamine in the body, reducing or even eliminating the smell.


No eggs on a TMAU diet.


Phenylketonuria (PKU)

Phenylketonuria (or PKU) is a rare genetic disorder that causes a defect in the enzyme that breaks down the amino acid phenylalanine. This causes phenylalanine to build up in the system to dangerous levels.

The build-up of phenylalanine in the system causes urine, skin, and breath to smell musty. This may cause a fishy smell in the urine.


Other Symptoms

In addition to the musty smell, the build-up of phenylalanine in the system can cause intellectual disabilities, developmental delays, mental health problems, eczema, neurological issues, weak bones, and microcephaly (a small head).



PKU is normally diagnosed through a simple, standard blood test in infants 1-2 days after birth. If PKU is not diagnosed, infants may develop symptoms including brain damage.



PKU can be managed through a diet that limits the intake of phenylalanine. People with PKU will need to stay on this diet throughout their lives. However, those with more minor cases may not need to be quite as restricted.


Got PKU? Get rid of the beans.



Hypermethioninemia (or MET) is a condition where the amino acid methionine builds up in the body. This is usually caused by a metabolic disorder in which the body cannot break down methionine, but it can also be caused by certain medications or as a side effect of liver disease. People with hypermethioninemia may have a cabbage-y or fishy smell to their sweat, breath, or urine.


Other Symptoms

Many people with MET have no symptoms. However, other potential symptoms include neurological problems, developmental delays, poor motor skills, liver issues, muscle weakness, and fatigue.



Babies are typically screened for hypermethioninemia a few days after birth. Otherwise, MET can be diagnosed with a blood test.



People with MET will need to eat a restricted diet so that methionine does not build up in the body to dangerous levels.


Beef: it’s not for dinner if you have MET.


When to See a Doctor for Fishy Urine Smells

Are you thinking, “My pee smells like fish! Should I go to the doctor?” Here are three signs that you should see a medical professional:


The Smell Doesn’t Go Away

If your urine smells fishy for more than a few days, it could be a sign of an underlying problem. This is especially true if you’ve already implemented some lifestyle changes like drinking more water and cutting down on alcohol and caffeine and there’s still no change.


You’re Having Other Symptoms

If you notice other symptoms accompanying your fishy-smelling urine, that’s another sign of a potential medical issue. So if you notice other changes or discomfort related to your urine, malaise, headaches, fever, nausea, or other signs of illness, see a doctor.

If you are experiencing severe abdominal pain or a high fever, go to the emergency room because these are signs of a medical emergency.


You Think You Might Be Pregnant

If you think your pee smells like fish because you could be pregnant, go to a doctor to confirm. Getting early prenatal care is an important component of healthy pregnancy outcomes. (Finding out earlier is also important if you wish to terminate your pregnancy).


Excuse me, ma’am, but are you old enough to be a doctor?


Why Does My Pee Smell Like Fish? The Bottom Line

You may be really worried if your urine smells fishy. However, many causes of pee that smells like fish are totally harmless. Many other causes are very easily treated.

Benign causes of fishy-smelling pee include minor dehydration, alcohol and caffeine consumption, and your diet.

Some common causes of fishy-smelling pee that may require a consultation with a doctor include supplements or medications, a UTI, bacterial vaginosis, STIs, prostate infection, pregnancy, and kidney stones.

The rarest causes of fishy-smelling pee include liver disease and metabolic disorders like trimethylaminuria, PKU, and MET.

Finally, here are some signs that you should go to a doctor if your pee smells like fish:

  • Your fishy-smelling pee won’t go away even with lifestyle changes like diet and hydration.
  • You are having other symptoms in addition to the fishy-smelling pee, like pain with urination, frequent urge to urinate, abdominal pain, or fever.
  • You suspect you might be pregnant.


What’s Next?

Other worrisome symptoms down there? Learn what white discharge, brown discharge, and bleeding during sex can mean.

Wondering how girls pee? What about how to tell if your hymen is broken? We can also tell you how to put in a tampon, how to masturbate, and how to finger yourself.

Learn how to interpret green poop, pain under your left breast, and pain during ovulation.

If you’re pregnant, learn more about what you’re supposed to expect when you’re 15 weeks pregnant and when you’re 34 weeks pregnant.