Stinky urine usually comes down to one of two things: you’re not drinking enough water, or something you ate is passing through your system. Less commonly, it signals an infection or a metabolic issue worth paying attention to. The good news is that most causes are harmless and temporary.
Dehydration Is the Most Common Cause
Your kidneys filter waste products out of your blood and dissolve them in water to create urine. When you’re well hydrated, those waste products are diluted, and your pee is pale with a mild smell. When you haven’t had enough fluids, your kidneys conserve water by producing less of it, which concentrates all those waste chemicals into a smaller volume. The result is darker urine with a much stronger odor.
The main chemical behind normal urine smell is urea, a nitrogen-rich compound your body produces when it breaks down protein. Urea itself is relatively mild, but it gradually converts into ammonia through a process called ureolysis. Concentrated urine has more urea per drop, which means more ammonia and a sharper, more pungent scent. In dehydrated people, ammonia levels in urine can climb significantly. If your pee smells strong and looks dark yellow or amber, drinking more water throughout the day will often fix the problem within hours.
Foods That Change Urine Smell
Asparagus is the most well-known offender. It contains a compound called asparagusic acid that your digestive system breaks down into sulfur-containing byproducts. Those byproducts pass into your urine and produce a distinctive, almost rotten smell that can show up within 15 to 30 minutes of eating. Interestingly, only 20% to 50% of people notice this effect. Some people may not produce the sulfur compounds at all, while others lack the specific smell receptors needed to detect them.
Asparagus isn’t alone. Coffee can give urine a bitter, concentrated smell because your kidneys filter out some of its aromatic compounds. Garlic, onions, and cruciferous vegetables like Brussels sprouts are all high in sulfur and can temporarily change urine odor. Certain spices, particularly cumin and curry, can do the same. These food-related smells are completely harmless and clear up once your body finishes processing the meal.
Urinary Tract Infections
When bacteria colonize the bladder or urethra, they break down chemicals in your urine and release their own byproducts, which can produce unusual and unpleasant smells. Depending on the bacterial strain involved, the odor can range from a strong ammonia or chemical scent to something savory, almost like chicken broth, or sulfurous like garlic. The smell alone doesn’t tell you which bacteria are responsible, and urology guidelines are clear that odor by itself isn’t enough to diagnose an infection.
What makes a UTI more likely than just a bad day of hydration is the combination of symptoms. If your stinky urine comes with a burning sensation when you pee, a constant urge to go, cloudy or pinkish urine, lower abdominal pressure, fever, chills, or back pain, those are signs that bacteria are involved. UTIs are especially common in women due to shorter urethral anatomy, but they can affect anyone.
Sweet or Fruity Smell and Diabetes
A sweet or fruity urine odor is a more specific warning sign. When your body can’t use glucose for energy (either because it doesn’t produce enough insulin or can’t respond to it properly), it starts breaking down fat as a backup fuel source. That process produces chemicals called ketones, which are acidic and have a distinctive smell. The primary ketone your body makes is acetone, the same chemical found in nail polish remover, which is why the scent is often described as sweet, fruity, or chemical-like.
This happens most often in unmanaged type 1 diabetes, but it can also occur in type 2 diabetes during periods of illness or severe blood sugar spikes. If you notice a persistent sweet smell in your urine, especially alongside increased thirst, frequent urination, fatigue, or nausea, it could indicate a condition called diabetic ketoacidosis, which requires prompt medical attention.
Liver Problems and Musty Odors
When the liver isn’t functioning well, it struggles to process certain sulfur-containing compounds that normally get broken down and cleared from the body. These compounds, particularly dimethyl sulfide and methyl mercaptan, accumulate and get expelled through breath, sweat, and urine. The resulting smell is often described as musty and oddly sweet, or like a combination of rotten eggs and garlic. This condition, known as fetor hepaticus, is associated with significant liver damage and is typically accompanied by other symptoms like jaundice (yellowing of the skin and eyes), abdominal swelling, confusion, and extreme fatigue.
Rare Genetic Conditions
A persistent fishy smell in urine, sweat, and breath can point to a genetic condition called trimethylaminuria. People with this condition have a deficiency in a liver enzyme responsible for converting a compound called trimethylamine into an odorless form. Without that enzyme working properly, trimethylamine builds up and gets released through bodily fluids, producing a strong fish-like odor. The condition is caused by variations in a specific gene (FMO3) and is present from birth, though it can sometimes become more noticeable during puberty or hormonal changes. It’s rare, but if you’ve dealt with an unexplained fishy smell for most of your life, it’s worth mentioning to a doctor.
Medications and Supplements
B vitamins, especially B6, are notorious for giving urine both a bright yellow color and a stronger smell. Antibiotics like amoxicillin and ciprofloxacin can alter urine odor as your kidneys filter them out. Sulfonamide drugs produce sulfur-containing metabolites that change the scent. Even high-dose vitamin C supplements can make urine smell different as excess amounts pass through.
If you recently started a new medication or supplement and noticed a change in urine smell, that’s likely the cause. The smell should return to normal after you finish the course or stop the supplement.
How to Tell if It’s Serious
Most of the time, stinky urine is your body telling you to drink more water or reminding you what you had for dinner. A one-off change in smell that resolves within a day or two is rarely anything to worry about. The picture changes when the smell persists for several days despite good hydration, or when it arrives alongside other symptoms: pain or burning during urination, fever, chills, back pain, blood in the urine, unusual thirst, or unexplained weight loss. Those combinations suggest something beyond diet or dehydration is going on and warrant a urine test to check for infection, glucose, or ketones.