Urine is primarily water, but it also serves as the body’s main route for excreting waste products, including various volatile organic compounds (VOCs). These compounds are byproducts of normal metabolism, and their concentration dictates the strength and character of the odor. When VOCs are present in unusual amounts, the resulting scent may be distinctively sweet or malty, which some people describe as smelling like Cheerios or a similar breakfast cereal. This change in scent can be a temporary effect of diet or a more persistent sign of an underlying metabolic process.
Transient Causes: Diet and Hydration
The most frequent reason for a sudden, sweet-smelling urine is related to the balance of water in the body. When fluid intake is insufficient, urine becomes highly concentrated, which intensifies the smell of any compounds present. Dehydration alone can make the natural waste products more pungent, but it especially amplifies any sweet or fruity notes that might be present.
A high intake of certain foods can also produce a temporary sweet aroma. Diets that are very low in carbohydrates, such as the ketogenic diet, force the body to burn fat for energy, generating byproducts called ketones. These ketones, including acetone, are excreted in the urine and on the breath, giving off a distinct sweet or fruity scent. Similarly, a large consumption of processed foods or sweets containing high amounts of simple sugars or malt-like flavorings can lead to the increased excretion of these substances, resulting in a malty or cereal-like smell.
The transient nature of these changes is a distinguishing factor. If the sweet smell appears shortly after a dietary change or poor hydration and resolves once normal intake is resumed, it is typically not a cause for concern. The body quickly processes and eliminates these compounds, returning the urine odor to its usual profile.
Medications and Supplements That Alter Scent
Several non-dietary substances ingested daily can also lead to noticeable changes in urine odor as they are metabolized and excreted. Supplements from the B-vitamin complex are well-known to alter the scent of urine. Excess amounts of thiamine (B1) and other B vitamins are water-soluble and rapidly eliminated by the kidneys, often producing a strong, sometimes pungent or chemical smell.
Certain prescription medications can also introduce a sweet scent into the urine. A class of diabetes drugs known as SGLT2 inhibitors works by blocking the reabsorption of glucose in the kidneys. This mechanism intentionally causes glucose to be excreted in the urine, a condition called glucosuria. The presence of this unabsorbed sugar in the urine creates the sweet or fruity aroma, which is a direct effect of the drug’s intended action.
Underlying Medical Explanations
While transient causes are common, a persistent sweet or malty urine odor warrants medical investigation, as it can indicate an underlying health issue. The most frequent medical cause is undiagnosed or poorly controlled diabetes mellitus. When blood sugar levels are excessively high, the kidneys attempt to flush out the surplus glucose, causing the sugar to “spill” into the urine.
This excess glucose imparts the sweet, sometimes fruity or cereal-like smell. In a more severe complication called diabetic ketoacidosis (DKA), the body produces a high concentration of ketones due to a lack of insulin. The rapid breakdown of fat releases high levels of ketones, such as acetone, which saturate the urine and cause a pronounced fruity or sweet smell. DKA is a medical emergency that often presents alongside symptoms like excessive thirst, fatigue, and confusion.
A much rarer, but serious, genetic condition is Maple Syrup Urine Disease (MSUD). This metabolic disorder prevents the body from properly processing certain amino acids—leucine, isoleucine, and valine. The accumulation of these byproducts gives off a distinct, sweet smell often compared to maple syrup, caramel, or burnt sugar. MSUD is typically diagnosed in infancy and requires lifelong dietary management to prevent neurological damage. A sweet odor that lingers despite changes to diet and hydration, especially when accompanied by other symptoms like increased thirst, unexplained weight loss, or fatigue, should prompt an immediate consultation with a healthcare provider.