All the Stuff That Makes Your Pee Smell—and What It Means

From eating too much asparagus to dangerous internal leakage.


We’ve written before about how the color of your pee can indicate the presence of life-threatening ailments—or in less serious cases, it can remind you what you ate for dinner last night. But its scent is just as telling: Below, you’ll find every cause of weird-smelling pee, from certain foods and drinks to drastic health problems, like internal leakage.

Asparagus: This is the classic culprit behind many a smelly pee, and it results from sulfuric compounds that are created during the digestion of asparagusic acid. But, strangely, asparagus doesn’t make everyone’s pee smell. Scientists aren’t totally sure why that is, but it’s likely because some people’s bodies contain an enzyme that breaks down asparagus in a certain smelly way, while other people’s bodies don’t.

Coffee: While there’s no conclusive scientific explanation for why your pee smells like coffee after drinking a pot of the stuff, there’s a theory: Caffeine is a diuretic, which means it causes you to urinate more often (which can lead to dehydration, and therefore, extremely concentrated urine). A small percentage of the caffeine we consume is also excreted, unchanged, in our pee. These two factors combined might create concentrated urine filled with coffee byproducts that have retained their smell. Whatever helps wake you up, right?

Garlic and Onions: Much like coffee, garlic and onions contain chemicals that retain their odour throughout the digestive process, which isn’t surprising considering how much of a stink they leave in our mouths. Garlic notably produces a strong-smelling compound called allyl methyl sulfide when metabolized, which is the same culprit behind lingering garlic breath.

Dehydration: When you’re not drinking enough water, your pee will reek of ammonia (for reference, many household cleaners contain ammonia). That’s because urine becomes concentrated with waste products (like ammonia) when it isn’t diluted with water. Rehydrate, and the smell should return to normal.

Infections: Foul-smelling urine can indicate the presence of urinary tract infections and bladder infections, which is reason to pay your doctor a visit. Note: This isn’t just strong-smelling pee (like that caused by dehydration), this is bad-smelling pee (think rotten fruit or the bottom of a stagnant pond) caused by the presence of bacteria.

Diabetes: “Diabetic patients don’t filter out as many waste products, so their urine isn’t going to be as filtered as it would be in a person who has properly functioning kidneys,” explains nurse practitioner, Anne Calvaresi. This results in excess sugar and glucose in the urine, which puts out a sweet smell. Fun fact: Back in the day, doctors performed urine taste tests to confirm whether or not their patients had diabetes.

Internal Leakage: A fistula is an abnormal passage between two organs (or an organ and the skin), which can result from injury, infection, surgery or inflammation. In simpler terms, this is a connection between two body part that aren’t meant to be connected—for example, an anal fistula is an irregular passageway between the anus and the skin, essentially giving you a second butthole (seriously).

Fistulas can cause serious internal leakage: “A vesicorectal fistula is a communication between the rectum and the bladder,” Calvaresi explains. “In that case, you can see stool in the urine or urine coming from the rectum—or both.” This can lead to the presence of faecal bacteria in the urine, which (obviously) presents a foul smell. If left untreated, nerve damage, infection and kidney failure are all associated with fistulas.

In short, if your pee doesn’t smell normal (whatever that may be)—and you haven’t consumed large amounts of the foods and drinks listed above—give your doctor a call. It could save you a lot of trouble in the long run.