Normal urine has a mild, slightly acidic smell that most people would describe as faintly “nutty” or just plain unremarkable. When you’re well-hydrated, your pee may have almost no odor at all. The smell comes from waste products your kidneys filter out of your blood, and how strong it is depends largely on how concentrated those waste products are.
What Gives Urine Its Normal Smell
Urine is mostly water, but it also contains urea, a byproduct of protein breakdown, along with other filtered waste. When your urine is dilute (pale yellow to straw-colored), there’s enough water to keep those waste products from producing much scent. When you haven’t been drinking enough fluids, the ratio shifts: less water, more waste. That concentrated urine carries a stronger ammonia-like smell because urea can break down into ammonia.
This is the single biggest reason urine smells different from one bathroom trip to the next. Your first pee of the morning is almost always the strongest-smelling because your body has been concentrating urine overnight. If your urine is dark yellow and pungent, drinking more water will usually resolve both the color and the smell within a few hours.
Foods That Change the Smell
Asparagus is the most famous offender. After you eat it, your body breaks down a compound called asparagusic acid into sulfur-containing molecules, the most prominent being methanethiol. The result is a distinctive sulfurous smell, similar to cooked cabbage, that can show up in your urine within 15 to 30 minutes of eating. About 8% of people don’t produce the odor at all, and roughly 6% of people can’t detect it even when it’s there, so the experience varies from person to person.
Coffee is another common one. It contains aromatic compounds that pass through your system largely intact. Garlic, onions, and certain spices can also lend a temporary odor. These food-related changes are harmless and clear up once the food has been fully processed, typically within a day.
Vitamins and Medications
B vitamins are well known for changing both the color and smell of urine. Vitamin B6 gives urine a noticeable musky scent, while supplements high in thiamin (B1) or choline produce a similar effect. If you’ve ever started a multivitamin and noticed your pee suddenly smells different and turns bright yellow, that’s almost certainly the B vitamins at work. Certain chemotherapy drugs can also alter urine odor. These changes are expected and not a sign of a problem.
Strong Ammonia Smell
A sharp ammonia smell is one of the most common concerns people have about their urine, but it’s usually just a sign of dehydration. When you don’t drink enough fluids, waste products become more concentrated and the ammonia scent intensifies. Eating a high-protein diet can amplify this further because more protein means more urea for your kidneys to process.
If you’re consistently noticing a strong ammonia odor even when you’re well-hydrated, it’s worth paying attention. A persistent pungent smell can sometimes signal a urinary tract infection. Bacteria, most commonly E. coli (responsible for 80% to 90% of UTIs), produce ammonia as they multiply in the urinary tract. A UTI typically comes with other symptoms too: burning during urination, frequent urges to go, cloudy or discolored urine, and sometimes pelvic pain.
Sweet or Fruity Smell
Urine that smells sweet or fruity can be a sign that your body is burning fat for energy instead of sugar, producing waste products called ketones. This happens most notably in uncontrolled diabetes. When blood sugar rises above roughly 250 mg/dL, ketones can spill into the urine and produce that characteristic sweetness. Left unchecked, this can progress to a dangerous condition called diabetic ketoacidosis, which brings nausea, vomiting, abdominal pain, shortness of breath, and confusion.
A sweet smell doesn’t automatically mean diabetes. Very low-carb or ketogenic diets can also produce ketones in urine, and so can prolonged fasting or heavy alcohol use. The difference is context: if you’re not intentionally restricting carbs and you notice persistently sweet-smelling urine, especially alongside increased thirst or frequent urination, that combination warrants testing.
In newborns, a distinctly sweet smell resembling maple syrup points to a rare inherited condition called maple syrup urine disease. It occurs when the body can’t properly break down three specific amino acids (leucine, isoleucine, and valine), causing them and their byproducts to accumulate. This is typically caught through newborn screening.
Musty or Unusually Foul Smell
A sweet, musty odor in urine (and on the breath) can be a feature of severe liver disease. When the liver can’t properly process certain amino acids, sulfur-containing compounds build up and get excreted, creating a smell sometimes described as “mousy.” This is not a subtle change. It typically occurs alongside other obvious signs of liver failure like jaundice, swelling, and confusion.
A foul or fishy smell that persists for more than a day or two, doesn’t respond to increased water intake, and isn’t explained by food or supplements deserves attention. Combined with pain, fever, blood in the urine, or changes in urination frequency, a persistent unusual odor can point to infections or other conditions that benefit from early treatment.
Pregnancy and Urine Smell
Many pregnant women report that their urine smells stronger or different, but the science behind this is more nuanced than it seems. While anecdotal reports of heightened smell during pregnancy are extremely common, lab testing has consistently failed to confirm that pregnant women actually have lower detection thresholds for odors. Studies comparing pregnant and non-pregnant women found no significant differences in their ability to detect smells. The experience appears to be more about perceived sensitivity, a subjective shift in how bothersome or noticeable smells become, rather than an actual change in the nose’s performance. Hormonal changes during pregnancy can also increase urine concentration due to shifts in fluid balance, which may contribute to a genuinely stronger scent.
What “Normal” Actually Looks Like
Healthy urine is pale yellow to straw-colored with a mild odor that you might not even notice if you’re well-hydrated. Temporary changes after eating asparagus, taking vitamins, or drinking coffee are completely expected. A stronger ammonia smell after a night’s sleep or a long stretch without water is normal too. The signals worth paying attention to are persistent changes that last more than a couple of days, especially a sweet or fruity smell you can’t explain, a strong foul odor that doesn’t improve with hydration, or any new smell paired with pain, fever, or changes in how your urine looks.