Why Does Cat Urine Smell So Bad?

Last Updated on August 6, 2021 by Julia Wilson

Anybody who shares their home with a cat who uses a litter tray or who has experienced a cat spraying knows that cat urine has a unique and pungent odour compared to that of our canine companions.

Urine is produced by the kidneys which filter waste products out of the blood, which pass through the ureters and into the bladder, which is then expelled during urination. Urinary waste products include urea (a waste product of protein metabolism), creatinine, uric acid, sodium and other electrolytes.

Causes of strong-smelling cat urine

Cat urine is concentrated

Cats are a desert-dwelling animal whose water intake was mostly obtained via the food they eat and not via water consumption. As a result, the cat’s kidneys evolved to conserve water by concentrating the urine. Concentrated urine contains high levels of waste products.

You may have noticed when you go to the toilet in the morning, your urine is quite dark, as you drink during the day, the colour of the urine becomes paler as it is less concentrated. Urine specific gravity (USG) is a measurement of urine concentration compared to that of pure water. Normal USG in cats is between 1.001 to >1.085 while in humans it is 1.010 to 1.030.


The characteristic ammonia odour develops when an enzyme (urease) producing bacteria break down urea in cat urine which releases ammonia into the environment.


Feline is a sulphur-containing amino acid, 2-amino-7-hydroxy-5,5-dimethyl-4-thiaheptanoic acid which is regulated by testosterone, a hormone that is mainly produced by the testicles. It is thought to be a precursor of cat pheromones and may play a role in territorial marking and acts as a conspecific recognition and reproduction. Females and neutered males produce much less felinine than the tomcat and levels are undetectable in kittens of any sex.

Feline is odourless however it develops the characteristic catty odour during the degradation of felinine which generates pyruvic acid and ammonia. During the second stage of decomposition, thiols are created, which is the same compound that gives skunk spray its foul odour and is often added to natural gas to make it easier to detect a gas leak.

Urinary tract infection

A bacterial infection of the urinary tract can lead to strong-smelling urine in addition to cloudy urine, frequent urination and urinating outside the litter tray.


Sulfa drugs can give urine a strong smell, this includes sulfa antibiotics and vitamin B.

What can be done about it?

We can’t do much to change the composition of cat urine, but there are ways to reduce the smell of cat urine in the house. As always, seek veterinary attention if your cat has an unusually strong urine odour or is urinating outside the litter tray or spraying.

Increase water consumption

Diluting the urine can help, encouraging the cat to drink is not always successful, but the introduction of a water fountain can encourage some cats to drink. Switching from a dry to a canned or raw diet can also

Clean litter trays frequently

Remove urine from the litter tray as quickly as possible before it begins to degrade and release odours.

Urine cleaners

For urine outside the litter tray or spraying, it will be necessary to purchase a suitable product designed to clean cat urine. These products contain naturally occurring non-pathogenic bacteria to rapidly consume the food source in urine (and remove odours) or germicides to break down the urine and kill urease producing bacteria.

This is done by seeding and inoculating the area with non-pathogenic bacterial cultures (incorrectly called enzymes). The logic being that the introduced bacteria will rapidly consume the food source in urine and hence consume the source of odours.

Blot as much cat urine as possible with a paper towel or sponge before applying the product.

If the urine has dried, a black light can illuminate areas where cat urine is present.  Cat urine will be found on horizontal surfaces such as carpet and bedding while cat spray will be on vertical surfaces including walls, doors, windows and cupboards.


Neutering reduces the tomcat smell of urine due to felinine as well as prevents several diseases and unwanted kittens.

Avoid ammonia-based products

Do not use products that contain ammonia, as it is a component of cat urine, using ammonia-based products can encourage cats to urinate or spray on the cleaned area.