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Feline diabetes mellitus is one of the most common endocrine conditions in cats and it occurs due to either a lack of production of the hormone insulin, or due to insulin not working effectively. Insulin is normally produced by specialised cells in the pancreas which is an organ located close to the liver and stomach. Insulin is a vital hormone for maintaining steady blood sugar (glucose) levels and for transporting glucose into the body’s cells to be used for energy.

If there is not enough insulin produced by the pancreas, or if insulin becomes ineffective then the blood sugar levels rise very high, and glucose cannot be transported into cells for energy meaning the body starts to try and utilise other sources of energy by breaking down fats.

There are some known risk factors in cats that can predispose them to developing diabetes:

• male cats are more commonly affected than females
• obesity, sedentary lifestyle
• chronic pancreatitis
• other hormonal diseases (such as hyperthyroidism, Cushing’s disease, and acromegaly)
• certain medications (e.g. megoestrol acetate and corticosteroids)
• certain breeds – Burmese cats in New Zealand, Australia, and the UK

Symptoms of feline diabetes 

The most common symptoms seen in diabetic cats are:

• Increased urination
• Increased drinking
• Weight loss
• Increased appetite

Other subtler, less common symptoms can include

• Poor coat quality
• Weakness in the hind legs, inability to jump, “sunken hocks” due to a diabetic neuropathy
• Secondary bacterial cystitis due to increased glucose in the urine, seen as straining to urinate, or discolouration of the urine

Diagnosis of diabetes 

Diabetes cannot be diagnosed based on the symptoms alone, as there are a number of conditions that can cause these signs. Diagnosis is made based on a combination of blood and urine tests.

A blood test in a diabetic cat will show a very high concentration of glucose however, this can also occur with stress so in some cats it may be necessary to repeat a blood glucose measurement on another day, or alternatively perform another blood test called fructosamine test. This test gives an indication of the blood glucose levels over the preceding 2-3 weeks.

Urine testing will show the presence of glucose in the urine, and in more severe or advanced cases there may also be ketones which are the by-product of fat metabolism.

Other tests that are indicated to further assess for underlying disease including thyroid testing, abdominal ultrasound to assess for pancreatitis, and urine culture.

Treatment of diabetes in cats

Although diabetes is a treatable condition, it is also a complex disease that needs a high level of commitment from both the cat’s care giver and their vet to ensure that management is tailored specifically to the individual cat.

• Insulin

Most diabetic cats will need to receive daily or twice daily insulin injections. To initially start your cat on insulin, your vet will admit your cat into hospital for 1-3 days to give the first injections while carefully monitoring your cat’s blood glucose levels over the day. Once your vet has ensured that the initial insulin dose is not too strong, you will then be shown how to draw up the insulin dose yourself and administer to your cat. Many owners are surprised how easy the insulin injections are to give as the needles are very small and generally most cats do not feel them.

One week after starting on the initial insulin dose, your cat will need to return to the vets intermittently to be reassessed where they will perform a physical exam, weight check, repeat blood glucose curves and slowly titrate the insulin dose to the correct level. Other testing may also be indicated from time to time such as urine testing, fructosamine testing and ultrasound. It may take weeks to months for diabetes to stabilise depending on the cat.

There are a number of different types of insulin available but most cats tend to stabilise best on the longer acting types such as insulin glargine (Lantus). It is important that the insulin is stored and handled properly as it can lose it efficacy. The vial needs to be kept in the fridge at all times in an area of the fridge where it will not freeze. Prior to drawing up the dose gently mix the vial but ensure never to shake it as this can damage the insulin. Lantus insulin should be a clear solution without any sediment or cloudiness.

• Dietary management

Diabetic cats that are fed a low carbohydrate diet will generally stabilise more quickly and will often need less insulin. There are a couple of commercial diets designed for this purpose, Royal Canin Diabetic, and Hill’s M/D diet.  Some diabetic cats that are fed low carbohydrate diets may actually go into “remission” where they no longer require insulin injections. This occurs most commonly in newly diagnosed cases and thus it is important that your cat is closely monitored especially in the early stages of treatment.

For diabetic cats that are overweight, it is crucial to that they commence a gradual weight loss program. Excessive body fat causes insulin resistance and in some diabetic cats, weight loss can significantly lower their insulin requirements or even result in remission of the diabetes.  It is important that any weight loss plan is performed in conjunction with your vet to ensure it is performed safely. If cats lose weight too quickly they can be prone developing a severe form of liver disease called hepatic lipidosis.

Timing of feeding with cats is less important than in humans and dogs, although this does somewhat depend on their diet and insulin type. It is recommended to continue to feed your cat in the way it has been used to.

 Home monitoring of the diabetic cat

Cat owners play a very important role in the management of their cat’s diabetes. It can be of great help to your vet if you can keep a daily diary detailing the following about your cat:

• Dose and time of insulin injections
• How much food is eaten and what type.
• General behaviour and mood of your cat, especially if more sleepy than usual
• Any vomiting, diarrhoea, or other signs of illness
• Water intake or amount of urination
• Body weight, if possible measure weekly
• Urine glucose – your vet can provide you with test strips to check for glucose in the urine
• Home blood glucose testing can be performed by some owners (and accepted by some cats) to allow the blood glucose curves to be performed without the need for repeated hospitalisation. Discuss with your vet if you think you may be able to do this.

You should never change your cat’s insulin dose without discussing with your vet first. Long acting insulin types such as glargine can take up to a week to take full effect after a dosage adjustment has been made.

It is important to know the symptoms of hypoglycaemia (low blood sugar) as this can be a dangerous and life threatening complication of diabetes. Hypoglycaemia can occur if your cat receives too much insulin, or alternatively your cat doesn’t eat their usual amount of food, or if you cat goes into diabetic remission without a reduction of their insulin dose.

Symptoms of hypoglycaemia are:

• Weakness, lethargy, lack of coordination, appearing “drunk”
• Glazed eyes, disorientated
• Convulsions or coma, can be fatal if untreated

If early signs of hypoglycaemia develop, it is crucial to immediately offer your cat some of their usual food to eat. If your cat is not able to eat, then administer some glucose syrup or powder onto their gums. If your cat is showing more severe signs of seizures or is comatose do not offer anything by mouth. Contact your veterinarian immediately.

Prognosis

The prognosis for a cat with diabetes is quite variable and will depend on how easy they are to stabilise, their age, and if they have any other underlying diseases. Diabetic cats require ongoing regular exams by your vet to ensure that they remain well managed. Provided the diabetes can be well managed, many cats with diabetes can have an excellent quality of life. Unfortunately not all cats can be stabilised well however, and these cases will benefit from more in-depth investigations for underlying causes.

Disclaimer: Please note that the information provided on this page does not replace the advice of your veterinarian. If you are concerned about your cat’s health in any way, we strongly recommend you seek veterinary advice. 

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