Urine that smells like popcorn is usually caused by high concentrations of ketones, compounds your body produces when it burns fat instead of sugar for energy. In most cases, the smell traces back to diet, mild dehydration, or both. Less commonly, it can signal uncontrolled diabetes or other metabolic issues worth checking out.
Ketones Are the Main Culprit
Your body’s preferred fuel source is glucose, which comes from carbohydrates. When glucose is in short supply, your body switches to burning stored fat instead. This process, called ketosis, produces three types of ketones: acetoacetate, beta-hydroxybutyrate, and acetone. These ketones circulate in your blood and eventually get filtered out through your kidneys into your urine.
Acetone is the one most responsible for that distinctive sweet, slightly toasted smell. It’s the same chemical found in nail polish remover, which is why some people describe the odor as fruity or chemical rather than specifically popcorn-like. But at lower concentrations, many people perceive it as a warm, buttery, popcorn-adjacent scent. When ketone levels in your urine rise, the smell becomes stronger and harder to miss.
How Diet Triggers the Smell
The most common reason for popcorn-scented urine is simply what you’ve been eating. High-protein, low-carb diets are the biggest driver. When you restrict carbohydrates severely, as on a ketogenic diet, your body ramps up fat burning and ketone production. Those ketones leave your body through both your breath and your urine, changing the way both smell.
Eating a lot of protein can intensify things further. Your body produces ammonia as a byproduct of breaking down protein, and ammonia combined with acetone creates a particularly strong odor. So if you’re eating low-carb and high-protein at the same time, you’re getting a double dose of odor-producing compounds.
Certain foods also contain a molecule called 2-acetyl-1-pyrroline, which is literally the compound that gives popcorn its signature smell. It has an extremely low odor threshold, meaning even tiny amounts are detectable by the human nose. This same molecule is found in aromatic rice (like basmati and jasmine), wheat bread, rye bread, and of course popcorn itself. After you eat these foods, trace amounts of the compound can pass through your system and end up in your urine. Coffee is another common trigger, since it contains hundreds of chemical compounds that your kidneys filter out.
Dehydration Concentrates the Odor
When you don’t drink enough water, your kidneys produce less urine but still need to excrete the same amount of waste. The result is more concentrated urine with a darker color and a stronger smell. Whatever odor-producing compounds are already present, including ketones and food byproducts, become more noticeable simply because they’re packed into less liquid. If your urine is dark yellow and smells like popcorn, drinking more water will often dilute the scent significantly.
Diabetes and Dangerously High Ketones
Sweet or popcorn-smelling urine can also be an early warning sign of diabetes, particularly when blood sugar levels have been running high for a while. In advanced or uncontrolled diabetes, the body can’t use glucose effectively, so it turns to fat burning even when there’s plenty of sugar in the blood. This drives ketone production to abnormally high levels. Sugar and ketones then accumulate in the urine together, creating a strong, sweet odor.
The more serious concern is diabetic ketoacidosis (DKA), a potentially life-threatening complication where ketone levels spike so high that the blood becomes acidic. DKA develops most often in people with type 1 diabetes, though it can occur in type 2 as well. The warning signs go well beyond urine smell and include fruity-smelling breath, nausea and vomiting, stomach pain, fast and deep breathing, extreme fatigue, flushed face, headache, and muscle stiffness. If you notice several of these symptoms together, especially alongside sweet-smelling urine, that’s a reason to get emergency medical care. The CDC recommends calling 911 or going to the ER if you’re vomiting and can’t keep fluids down, having trouble breathing, or showing multiple signs of DKA at once.
Other Possible Causes
Pregnancy can change the way urine smells for several reasons. Hormonal shifts alter metabolism, dietary preferences often change, and many pregnant women experience a heightened sense of smell that makes them notice odors they’d normally overlook. Prenatal vitamins, which typically contain B vitamins, can also contribute to urine odor changes.
B vitamins and vitamin D supplements are known to change urine smell and color even outside of pregnancy. If you recently started a multivitamin or B-complex supplement and noticed the popcorn scent, that’s a likely explanation.
A rare genetic condition called maple syrup urine disease (MSUD) causes urine, sweat, and earwax to smell sweet, like maple syrup or burnt sugar. While this is sometimes confused with a popcorn-like scent, MSUD is almost always diagnosed in infancy through newborn screening. It’s not something that suddenly appears in adults.
What to Do About It
If you’re otherwise feeling fine and the smell showed up after a dietary change or a day of not drinking enough water, it’s almost certainly harmless. Drinking more water and moderating protein intake will usually reduce or eliminate the odor within a day or two. People following a ketogenic diet should expect some degree of unusual urine smell as a normal side effect of sustained ketosis.
The smell becomes worth investigating if it persists for more than a few days despite good hydration, if you haven’t made any dietary changes that would explain it, or if it comes alongside other symptoms like increased thirst, frequent urination, unexplained weight loss, or fatigue. These can point toward diabetes or blood sugar problems. A simple urine test at a doctor’s office can check for both sugar and ketones and rule out anything serious quickly.