Does my cat have diabetes mellitus?

Does my cat have diabetes mellitus?

There is no typical, diabetic cat, and the diagnosis usually comes as a surprise to owners (and sometimes to vets as well).  Typical to many things in the cat universe, feline diabetes is difficult to diagnose and frequently a problem to control.  And since the cat quite often just stops being diabetic for variable lengths of time, the prognosis is as individual as the cat!

There is no single symptom that manifests either.  Believe it or not, they vary from no symptoms at all, to the classic diabetic feline ‘drinking and urinating a lot (PUPD in the jargon) with ravenous appetite’ to ‘skinny sick cat’.

Here’s an example of the confusing options…

  • The most common feline diabetes symptoms are actually lethargy (which is seen in nearly every feline problem!) and a poor hair coat.
  • Owners do not always know whether a cat is drinking more or more often (unless it is exclusively indoors) and the same goes for urinating more.
  • And an increase in appetite? Well, cats are always asking for food, so it takes a while to register that Kitty is actually eating all the food he’s demanded but is not getting any fatter!  
  • Weight loss is another insidious entity because often the cat appears only to change shape, with a bigger abdomen (due to liver enlargement and changed fat deposition) and thinning of muscle along the spine.
  • Uniquely, cats can concentrate their urine to a very high degree. This means there is more sugar in the urine and but concentrated to a lower volume of urine, so for many cats with diabetes, there may be no increase urinating.  And with cats being so good at conserving energy, there is often no weight loss either!

There are also other features or diseases associated with diabetes in cats, which means there are often combinations of problems going on in the same cat and these obviously cloud the diagnostic picture.

Renal failure commonly causes more drinking plus weight loss.  Diabetes occurs post-progesterone administration (once used regularly for oestrous control, behavioural modification and skin allergy treatments) and post-cortisone treatment. Hyperthyroidism, Cushings disease (hyperadrenocorticism – very rare in cats) and acromegaly (excess Growth Hormone, also rare but becoming more common as our feline friends live longer) can all present as diabetics initially.

Urine will probably be the first clue your cat may have diabetes mellitus. 

The increased urine is really what you will notice first because the litter has to be changed more often!

The glucose in the urine is also an excellent source of nutrition for bacteria, so urinary tract infections and bleeding from the bladder are also quite common in diabetic cats. This makes them urinate more frequently and with great volume, so both owner and cat become litter tray obsessed, or the cat will start peeing outside the tray.  It is just too wet or too painful to pee in the tray anymore.

As an example of the challenges a vet can experience, three of the diabetic cats I’ve seen have presented for cystitis – urinating outside the litter tray with blood in the urine. Maybe it was the only way they could draw attention to their problem!  Now, I make sure I test the urine of all cats who change their litter tray habits!

Why cats with diabetes drink and eat more, lose weight

Feline diabetes symptoms are classically the same for cats as in people – i.e drinks large amounts of water, eats more food and still loses weight, while still passing large volumes of urine.

Interestingly, the driving mechanism for the clinical signs is the urine and not the drinking, as one might assume.  Diabetics must drink large volumes of water because the excess glucose in the blood (no insulin to remove it for use in the tissues) gets filtered into urine by the kidneys.  Because glucose draws water with it (think of clumpy sugar in hot weather!), then water from the body is also dragged into the urine, so the body dehydrates.  Therefore, the cat has to drink more to counteract that effect.

The weight loss occurs because the glucose is the main source of calories for the body’s metabolism, and the calories in glucose are being eliminated uselessly in the urine.  The initial digestive processes are unaffected, so food which goes into the cat is still digested, but most of it comes out again as glucose in the urine.

Basically, the cat cannot eat enough to maintain its body weight, so there is weight loss along with increased thirst.

But, as I have already said, there are traps when diagnosing whether a cat has diabetes.  Even vets can be tricked.

How to confirm feline diabetes

The easiest and most common way to identify diabetes in cats is simply by routine or random urine (and blood) tests.

Waiting till a cat shows cat diabetes symptoms (especially by the time they stop eating or go into a coma in ketoacidosis) makes it much harder for treatment and creates a poor prognosis (long-term outlook for health). This is because their metabolism is so deranged they are producing ketones in their blood and urine.  

Diabetes in cats is becoming more common and is one of the reasons health checks, especially for older cats, is so important. A test in time may save (nine!) lives!


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The information we offer is educational in nature and is not intended as a substitute for professional medical prevention, diagnosis or treatment. Our recommendation is to always do your research.


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