Drinking plenty of water dilutes your urine, which reduces the concentration of waste products and typically makes it lighter in color and milder in smell. But hydration only addresses one variable. Several other factors, from the foods you eat to underlying health conditions, produce odor-causing compounds that persist in urine no matter how much water you drink.
How Hydration Actually Affects Urine Odor
When you’re well-hydrated, your kidneys produce more dilute urine. That dilution spreads the same waste products across a larger volume of liquid, which does reduce the intensity of the smell. But it doesn’t eliminate the compounds causing the odor in the first place. Think of it like adding water to a pot of soup: the broth gets thinner, but you can still taste the garlic. If your body is producing particularly pungent metabolites, dilution alone won’t make the smell disappear.
Foods That Create Strong Urine Odors
Asparagus is the most well-known culprit. It contains a compound called asparagusic acid that your body breaks down into sulfur-containing byproducts during digestion. Sulfur is the same chemical responsible for the smell of rotten eggs and skunk spray. Those byproducts evaporate almost immediately when you urinate, which is why the smell hits you right away. Asparagus pee can show up within 15 to 30 minutes of eating it and linger for up to 14 hours.
Coffee, garlic, onions, Brussels sprouts, and even soda can also change your urine’s scent. These foods produce metabolites that your kidneys filter into urine, and no amount of water intake neutralizes the chemistry. The odor fades once the compounds clear your system, usually within a day.
Vitamins and Supplements
B vitamins are a common and often overlooked cause of strong-smelling urine. They’re water-soluble, so your body excretes whatever it doesn’t need through urine. This often turns your pee bright yellow and gives it a distinct, sometimes foul smell. If you take a daily multivitamin or B-complex supplement, that alone could explain the odor you’re noticing. Other water-soluble supplements can have a similar effect.
Urinary Tract Infections
A UTI is one of the most common medical reasons for foul-smelling urine. Bacteria colonize the urinary tract and break down compounds in your urine, producing waste products with strong odors. One common bacterium, Proteus mirabilis, releases an enzyme that converts urea (a normal component of urine) into ammonia. That sharp, almost chemical smell is a hallmark of certain infections.
Other symptoms of a UTI typically include a burning sensation during urination, frequent urges to go, and cloudy or discolored urine. If you’re experiencing any of these alongside the smell, an infection is a likely explanation, and antibiotics will resolve it.
The Odor Might Not Be Coming From Urine
For people with vaginas, it’s worth knowing that the source of the smell may not be the urine itself. Bacterial vaginosis, a common condition caused by an imbalance of vaginal bacteria, produces a fishy odor that often worsens after sex. Because the vagina and urethra are close together, it’s easy to mistake a vaginal odor for a urinary one. The key difference: BV typically causes a thin grayish discharge, while a UTI causes burning or urgency during urination. Yeast infections can also produce noticeable odor, though they’re more commonly associated with itching and thick discharge.
Metabolic and Blood Sugar Issues
When the body can’t use glucose properly, as in uncontrolled diabetes, it starts breaking down fat for fuel instead. This process generates acids called ketones, which build up in the blood and spill into the urine. Ketones give urine (and breath) a distinctive sweet or fruity smell that’s quite different from the typical ammonia-like odor of concentrated urine.
This condition, diabetic ketoacidosis, is a medical emergency most common in people with type 1 diabetes, though it can occur in type 2 as well. If your urine has a persistent sweet or fruity scent and you’re also experiencing excessive thirst, nausea, or confusion, those are signs that your blood sugar needs immediate attention. Home urine test strips can detect elevated ketone levels.
Liver and Kidney Problems
Your liver and kidneys are responsible for filtering and processing waste. When either organ isn’t functioning well, unusual compounds can accumulate and change the way your body fluids smell. Advanced liver disease produces a characteristic musty, oddly sweet odor caused primarily by dimethyl sulfide and methyl mercaptan, the same compound that gives rotten eggs and cabbage their smell. This odor appears in breath, sweat, and urine. Kidney disease can similarly cause urine to take on an ammonia-heavy or otherwise unusual scent as waste products build up in the blood.
These conditions come with many other noticeable symptoms, including fatigue, swelling, skin changes, and appetite loss, so a smell change alone is unlikely to be the first sign. But persistent, unexplained changes in urine odor that don’t track with diet or supplements are worth investigating.
Rare Genetic Conditions
Trimethylaminuria, sometimes called fish odor syndrome, is a genetic condition where the body can’t break down a compound called trimethylamine. This chemical is produced by gut bacteria during digestion of eggs, fish, liver, and legumes. Normally, a liver enzyme converts trimethylamine into an odorless molecule. In people with this condition, the enzyme is missing or underactive, so trimethylamine builds up and gets released through urine, sweat, and breath, producing a strong fishy smell.
The condition is inherited, requiring a defective copy of the responsible gene from both parents. It’s rare, but if you’ve noticed a persistent fishy odor in your urine for most of your life that no amount of hydration resolves, it’s a possibility worth discussing with a doctor. Dietary modifications, specifically reducing intake of trimethylamine-rich foods, can significantly reduce the smell.
Pregnancy and Hormonal Shifts
Many pregnant people report that their urine smells stronger or different than usual, and this is commonly attributed to a heightened sense of smell during pregnancy. Interestingly, research doesn’t fully support that explanation. Multiple studies measuring actual olfactory detection thresholds found no significant difference between pregnant and non-pregnant women. What does seem to change is how the brain reacts to smells: pregnant people may be more aware of or bothered by odors they’d normally ignore, even if their nose isn’t technically more sensitive. Hormonal shifts during pregnancy also change urine composition, which can genuinely alter the scent. Prenatal vitamins, particularly their B-vitamin content, add another layer.
What to Pay Attention To
A temporary change in urine smell after eating certain foods or starting a new supplement is normal and harmless. The smell should resolve within a day once the trigger passes. What matters more is persistence and context. If the odor lasts more than a few days without an obvious dietary cause, or if it’s accompanied by pain, burning, fever, unusual discharge, or changes in urine color, those patterns point toward something that needs a closer look.
Keeping a brief mental note of when the smell appears, what you ate, and what supplements you took can help you (or your doctor) narrow down the cause quickly. In many cases, the answer turns out to be something as simple as a B-vitamin or last night’s asparagus, even when your water intake is perfectly fine.