What do a cat’s kidneys do

The kidneys have four main functions. Firstly, they regulate the cat’s water and salt balance. If the cat is dehydrated, they retain water – producing smaller amounts of more concentrated urine – whereas if they have drunk too much, the kidneys produce larger volumes of more dilute urine. At the same time, they control the amounts of various salts in the cat’s blood – sodium, potassium, calcium, phosphate and others.


They also have a vital role in getting rid of waste products. The most important are urea (a breakdown product from protein in the diet) and creatinine (a waste product produced by the muscles). These chemical wastes are actively concentrated in the cat’s urine.


As well as water balance, the kidneys also help to regulate blood pressure, via a cascade of enzymes in the blood that cause the blood vessels to constrict (raising the pressure) or dilate (dropping it).


Finally, they help to control the numbers of red blood cells in the blood by releasing a hormone called erythropoietin (of cycling cheat fame!) which tells the bone marrow to make more.

What causes kidney problems

There is a range of possible causes, including damage to the kidneys by infections or toxins; tumours in the kidneys; and some birth defects. There is also a genetic condition called polycystic kidney disease (PKD), where kidney tissue is progressively replaced with large fluid-filled cysts (it’s most common in Persians and related breeds).


However, in most cases, the cause is far simpler – degeneration due to old age and a high protein diet. As obligate carnivores, cats need a lot of protein in their diet to survive, but this means the kidneys have to work harder to remove the breakdown products than the kidneys of herbivores such as horses – so chronic, long-term damage is much more common. Kidney disease can be seen in cats of any age (Gizzy is 5 years old), but is most commonly seen in middle to old-aged cats (those over 7 years), and it becomes increasingly common with age. It has been estimated that around 20-50% of cats over 15 years of age will have some degree of kidney disease present and  is seen about three times more frequently in cats than in dogs.

Which cats are at risk

All cats – some estimates suggest that as many as half of all cats who reach 15 years old develop kidney problems. Even really well cared for pets are at the same risk. If you notice your cat drinking lots of water, however old it is, take him/her to the vet for a kidney test. It’s unusual to notice a cat drinking lots of water, so take it as a sign that something is wrong.

OK, so what are the symptoms

The symptoms are usually subtle and vague to begin with, but get gradually worse with time as more of the kidney tissue fails and more waste products build up in the blood. Also, cats are very crafty at hiding symptoms of feeling ill. Typical signs to look for include:

  • Weight loss

  • Increased thirst

  • Vomiting (due to the build-up of toxins)

  • Increased production of dilute urine; this may cause incontinence

  • Dehydration

  • Poor coat quality

  • Loss of appetite

  • Lethargy

  • Muscle weakness

  • Bad breath (often it smells metallic, as blood urea levels rise)

  • Hiding in dark places like a cupboard or under the sofa

Early diagnosis of kidney problems

Because kidney issues are so common in cats, routine screening of all mature and older cats can help early diagnosis, which in turn may prolong a good quality of life. Yearly or twice yearly routine veterinary check-ups are important, and as your cat begins to get older it is important that urine samples, and body weight, are monitored at each visit. A declining urine concentration or body weight may be early signs that the kidneys are struggling and that further investigations should be done. Blood tests (measuring urea, creatinine and/or SDMA)  and x-rays may also allow early detection of kidney trouble, especially when changes are monitored over time.

How can it be treated

Kidney disease in cats cannot be cured. However, it can be managed, with changes in lifestyle, diet, and medications. Kidney cats have higher than normal water requirements, so making sure they always have access to fresh water is vital. Some cats don’t like to drink still water, so there are a variety of water fountains available for them!

A specialist renal diet is really important – these are specially formulated to support the kidney’s function (less phosphate and protein, to reduce the kidney’s workload, and more potassium). 

Gizzls CBD treats will help tremendously with stimulating a cats appetite as this is crucial to their well-being. Gizzy’s appetite increased dramatically within days of me giving him CBD. 


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The information contained herein is not intended nor implied to be a substitute for professional medical advice, it is provided for educational purposes only. You assume full responsibility for how you choose to use this information. Always seek the advice of your vet before starting any new treatment or discontinuing an existing treatment. Talk with your vet about any questions you may have regarding a medical condition. Nothing contained herein is intended to be used for medical diagnosis or treatment.