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Urine odour

All information on the topic of urine odour

At a glance

Fresh urine generally smells neutral.
The typical smell of ammonia usually occurs when bacteria decompose the urine.

If fresh urine smells strong, this can have different causes.

If, for example, the fresh urine smells strongly of ammonia, this can be an indication of a urinary tract infection. A sweet smell indicates diabetes. With fishy smell, an infection in the genital area is often present, especially in women.

A smell of rotten eggs may be caused by a tumor in the urinary tract area.

Further information

The following odours in the urine should be observed in principle:

  • alcoholic urine odour
  • fish-like urine odour
  • sweet urine smell (after fruit)
  • sharp-biting urine odour after ammonia
  • rotten smell

The causes of the odors can be classified into causes

Urinary tract infection

In the case of a urinary tract infection or even cystitis, urine can smell stinging and sometimes fishy. Urinary tract or bladder infection tends to occur more frequently in women. Invaded bacteria decompose the urine, making it smell stronger. In addition to bacteria, viruses or fungi can also trigger an infection.


If the urine has an fruity smell, this can be a sign of metabolic derailment in the context of diabetes. Smell arises as a result of a so-called ketoacidosis,which indicates severe insulin deficiency.


The most well-known is the severe urine smell after eating asparagus. Foods such as garlic, cabbage, coffee or alcohol can also cause an unusual urine odour. This is mostly harmless and the smell evaporates again after the corresponding substances have been excreted.


Urine consists of 95 percent water and about 5% of filtrates and other ingredients. If the ratio of these ingredients is disturbed, color and smell change. If the urine is intensely coloured and smells very strongly of ammonia, this may indicate dehydration. In this case, the water content in the urine is lower and the urine is more concentrated. The darker the urine, the stricter its smell is often. Other signs of dehydration include low blood pressure and overheating.


Drugs such as penicillin also affect urine odour. Some patients report that the smell is unpleasantly smelly.


Tumors in the urinary tract, bladder or kidneys can cause a rotten smell in the urine. The smell is usually caused by cell decay.

If the urine smells extremely unpleasant, this is definitely an alarm signal and should be clarified directly.

Other symptoms include blood in the urine,constant urge to urinate, and the feeling of cystitis.


Phenylketonuria is a congenital metabolic disease in which the enzyme phenylalanine hydroxilase, formed in the liver, is defective.

Symptomatic of this condition is that the urine smells of mouse excrement or horse stables. A rapid diagnosis after birth and subsequent dietary treatment can ensure healthy development. Phenylketonuria is usually determined not by the urine but by the Guthrie test or tandem mass spectrometry after birth.

Maple syrup disease

Today, as with phenylketonuria, the diagnosis of maple syrup disease is made in extended neonatal screening programs using tandem mass spectrometry shortly after birth. The urine smells sweet-spicy during maple syrup disease and is reminiscent of maple syrup – from where the name also comes from. The disease causes a disturbed metabolism of the amino acids, which untreated can have very serious consequences.

See also: Urinary tract infection, bacteria in the urine, blood in the urine


  • Tena: Wenn der Urin riecht: Was verrät der Geruch des Harns?,
  • Gesenhues, S. et al. (2013) Praxisleitfaden Allgemeinmedizin. Urban & Fischer, Munich
  • Keller, C.K. & Geberth, S.K. (2010): Praxis der Nephrologie. Springer, Berlin
Status of information: Spring 2020