Sulfur-smelling urine is usually caused by something you ate or drank, not a serious medical problem. Foods rich in sulfur compounds, like asparagus, garlic, and onions, are the most common culprits. That said, a persistent rotten-egg smell that doesn’t trace back to your diet can sometimes signal a urinary tract infection, kidney stones, or, more rarely, a liver condition.
Foods That Cause Sulfurous Urine
Your body breaks down sulfur-containing compounds in food and excretes the byproducts through urine. Asparagus is the most well-known offender. Your body converts asparagusic acid (a compound unique to asparagus) into sulfur-containing molecules, giving your pee a skunky, rotten-egg scent. The smell can show up within 15 to 30 minutes of eating it.
Interestingly, not everyone notices. Depending on the study, only 20% to 50% of people report the smell after eating asparagus. Some people may produce the odor but lack the genetic ability to detect it, a trait called “asparagus anosmia.” Other sulfur-rich foods that can change how your urine smells include garlic, onions, Brussels sprouts, cabbage, and curry. Coffee and fish can also contribute a strong odor, though less specifically sulfurous.
Dehydration Makes It Worse
When you’re not drinking enough water, your urine becomes more concentrated. That means the same sulfur compounds from your diet are packed into a smaller volume of liquid, making the smell far more pungent. If your urine is dark yellow and has a strong sulfur odor, dehydration is likely amplifying whatever your body is already excreting. Drinking more water dilutes those waste products and typically reduces the smell within a few hours.
Urinary Tract Infections
A UTI can produce urine that smells foul, and some people describe it as sulfurous. Bacteria multiplying in the urinary tract generate waste products that alter the odor. You’ll usually notice other symptoms alongside the smell: a burning sensation when you pee, the urge to urinate more frequently than normal, and urine that looks cloudy or slightly bloody. Fever and mental confusion, particularly in older adults, are also telltale signs. If you’re experiencing any of these alongside the smell, it’s worth getting tested. UTIs are straightforward to treat but can get worse if ignored.
Kidney Stones Made of Cystine
A less common but notable cause is cystine kidney stones. Cystine is an amino acid that contains sulfur. Most people’s kidneys reabsorb cystine efficiently, but in a condition called cystinuria, a genetic defect in the kidney’s transport system lets cystine leak into the urine. Because cystine doesn’t dissolve well, it can crystallize into kidney stones. The sulfur in cystine gives urine a distinct rotten-egg smell, even before a stone forms.
Cystinuria affects roughly 1 in 7,000 people worldwide. It tends to cause recurrent kidney stones, often starting in the teenage years or early adulthood. If you’ve had multiple kidney stones and your urine consistently smells like sulfur, this is something worth bringing up with a doctor, since cystinuria requires long-term management to prevent repeated stone formation.
Liver Disease
In rare cases, a sulfur or rotten-egg smell in urine can point to serious liver problems. When the liver can no longer filter certain toxic substances from the blood, those compounds build up and get released through breath, sweat, and urine. Two of the key chemicals involved are dimethyl sulfide (which smells pungent and garlicky) and methyl mercaptan (which smells like rotten eggs or cabbage).
This distinctive odor, sometimes called fetor hepaticus, is most associated with chronic liver failure or decompensated cirrhosis, where permanent scarring has severely impaired the liver’s function. Acute liver failure can also cause it. People who develop this smell typically have other noticeable symptoms of advanced liver disease: jaundice, abdominal swelling, fatigue, and confusion. A sulfur smell in your urine alone, without these other signs, is very unlikely to indicate liver failure.
Medications and Supplements
Sulfa-based antibiotics and certain supplements can change urine odor. B vitamins are known for giving urine a strong, sometimes unusual smell. Supplements containing sulfur-based amino acids, like N-acetyl cysteine or methionine, can produce a sulfurous scent as your body metabolizes them. If the timing of the smell lines up with starting a new medication or supplement, that’s likely your explanation. The odor typically resolves once you stop taking it or your body adjusts.
How to Tell If It’s Harmless
The single most useful question is whether the smell goes away on its own. If you ate asparagus, garlic, or another sulfur-rich food, the odor should clear within a day, especially once you hydrate well. That’s completely normal and harmless.
The signs that something else is going on include a sulfur smell that persists for several days without a dietary explanation, pain or burning during urination, fever, chills, back pain, or urine that looks cloudy, dark, or bloody. These combinations suggest a UTI, kidney stones, or another condition that benefits from a urine test. A simple urinalysis can quickly distinguish between a harmless dietary byproduct and something that needs treatment.