What causes sweet smelling urine?

Causes of sweet-smelling urine include high concentrations of sugars or ketones, low urine volume, and certain dietary factors. Sudden development of a sweet or fruity odor in the urine is cause for concern as it indicates that something is wrong with the patient's metabolism. A doctor may take a urine sample for analysis and perform some other tests to learn more about the patient's condition and develop some treatment recommendations.

High blood sugar can cause a sweet-smelling urine as the kidneys express excess sugar in the urine to eliminate it. Diabetes is a common cause of high blood sugar, and some patients have high blood sugar that does not qualify them for a diagnosis of diabetes, but could put them at risk of developing the disorder. If patients notice excessive thirst along with changes in urine odor, diabetes is a culprit they should consider.

Ketones in the urine are another potential cause. This can happen during dieting, especially crash dieting, and is also a sign of malnutrition or starvation. These patients may have normal blood glucose levels, but still have sweet-smelling urine. If patients notice changes in urine odor along with dietary changes, ketones may be the cause, and a doctor can run a test to check the level of these compounds.

Low urine volume can be a potential cause. When patients don't drink a lot of water, their urine becomes concentrated and odors will be more noticeable. If the patient has not been drinking water and has been consuming a lot of sweet foods like fruits and baked desserts, the urine may smell slightly sweet. This is not necessarily a cause for concern, although it may be a warning sign to drink more water to prevent dehydration and kidney damage. The more diluted urine should not smell sweet in these cases.

The other cause of sweet-smelling urine is an underlying metabolic disorder. One of these disorders is known as maple syrup urine disease, after the distinctive odor associated with it. If an error in metabolism is causing the change in odor, the patient will likely have other symptoms as well. In patients with maple syrup urine, for example, there are also neurological symptoms and the patient will exhibit symptoms such as sweet-smelling urine shortly after birth, rather than developing them later in life. Patients at risk for metabolic disorders may undergo newborn screening for common disorders and risk factors.

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