Trimethylaminuria: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats trimethylaminuria (fish odor syndrome)?
A primary care doctor (family medicine or internal medicine) usually manages trimethylaminuria, also called fish odor syndrome, a condition that makes sweat, breath and urine smell fishy. The doctor can diagnose it with a urine test, suggest diet changes that reduce the smell, and refer patients to a medical geneticist to confirm the inherited cause if needed.
What is trimethylaminuria?
Trimethylaminuria, also called fish odor syndrome, is a disorder. The body cannot break down trimethylamine, a chemical with a strong smell. Trimethylamine has been described as smelling like rotten or decaying fish. As it builds up, it gives off a strong fishy odor in sweat, urine, and breath. It is an uncommon genetic disorder. It is also called TMAU for short.
Symptoms
The main symptom is a strong fishy body odor. The odor can come out in sweat, urine, breath, and reproductive fluids. The strength of the odor can change over time. Some people have a strong odor all the time, but most have a moderate smell that changes in strength. Other than the odor, people with this condition typically appear healthy.
The condition seems to be more common in women than in men. Symptoms can get worse around puberty. In women, they can worsen just before and during periods, after taking birth control pills, and around menopause.
The odor can affect relationships, social life, and work. Some people feel depressed and isolated because of it.
Causes and who gets it
Changes in the FMO3 gene cause most cases. This gene gives instructions for making an enzyme, a protein that speeds up a chemical reaction in the body. Normally, this enzyme turns strong-smelling trimethylamine into a molecule with no odor. If the enzyme is missing or works poorly, trimethylamine builds up in the body.
Gut bacteria make trimethylamine when they digest eggs, liver, soybeans, peas, certain fish, and other foods. Researchers believe that stress and diet also play a role in triggering symptoms. Other causes include too many of these bacteria in the gut, and, in a few adults, liver or kidney disease. Short-term symptoms were seen in a few premature infants and in some healthy women at the start of their periods.
Most cases are inherited in an autosomal recessive pattern, meaning both copies of the gene have changes. The parents usually carry one changed copy and typically show no signs. Carriers may have mild symptoms or short episodes of strong body odor.
How doctors diagnose it
Doctors use a urine test to diagnose it. The urine is checked for high levels of trimethylamine. The test is done on two separate occasions while you eat a normal diet. It compares trimethylamine with its odorless form. Gene testing can also look for changes in the FMO3 gene.
Treatment
Treatment aims to lower the odor. People with this condition can live normal, healthy lives. A main step is avoiding foods that contain trimethylamine or the building blocks the body turns into it. These foods include eggs, liver, kidney, peas, beans, peanuts, and soy products. They also include broccoli, cabbage, cauliflower, and brussels sprouts. Seafood has a compound that turns into trimethylamine, but freshwater fish have less.
Other steps can help too. Doctors may use low doses of antibiotics to reduce gut bacteria that make trimethylamine. Activated charcoal and copper chlorophyllin supplements may lower the trimethylamine in urine. Soaps with a moderate pH, between 5.5 and 6.5, can help. Avoiding things that cause sweating, such as exercise, stress, and emotional upsets, may also help.
It is important to follow the treatment advice of your health care provider.
When to see a doctor
Call 911 or go to the emergency room if you feel you may harm yourself. You can also call or text 988. See a doctor if you have a strong fishy body odor. It is also worth a visit if the odor affects your relationships, social life, or work. Tell your doctor if you feel depressed or isolated because of the odor.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Either can arrange a urine test and talk through diet changes. They can also refer you to a specialist in inherited conditions and follow up on how you are doing.
Common questions
What causes trimethylaminuria?
Trimethylaminuria is usually caused by an inherited gene change that stops the body from breaking down a compound called trimethylamine, so it builds up and leaves the body through sweat, breath and urine, causing a fishy smell. Diet and other factors can also affect symptoms.
Can a direct primary care doctor manage trimethylaminuria?
Yes, a direct primary care doctor can often diagnose trimethylaminuria with a simple urine test and suggest diet changes that reduce odor, such as limiting certain foods. For confirmation of the genetic cause, or if symptoms are hard to control, the doctor may refer you to a medical geneticist.
Is trimethylaminuria dangerous?
Trimethylaminuria is not physically dangerous, and other than the odor, people with it typically appear healthy. The main challenge is the fishy odor, which can affect confidence and social life. A doctor can suggest diet and lifestyle changes that often reduce the smell and make daily life easier.
Sources
- MedlinePlus Genetics - Trimethylaminuria
- National Human Genome Research Institute - About Trimethylaminuria
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
