Diabetes Mellitus in cats

What is Diabetes?

The clinical definition of diabetes in cats refers to a defect in carbohydrate metabolism most often associated with insulin resistance – similar to humans that develop Type -2 Diabetes.

Insulin is produced by the endocrine cells of the pancreas and is required to move glucose into cells – this results in a marked increase in blood glucose levels. As a result, the body (liver) will eventually start to produce ketones in lieu of glucose as they are smaller molecules, therefore easier to produce. Excessive ketones can result in DKA (diabetes ketoacidosis) as these molecules are acidic, they can disturb the acid-base balance of the body leading to severe illness.

Obesity is linked to the development of diabetes in cats through a reduction in insulin sensitivity leading to resistance. Genetic factors can also come into play, such as breed predilection – Burmese cats, for instance are at an increased risk.

How is Diabetes diagnosed?

Diagnosis requires a combination of clinical signs and laboratory findings. Increased drinking and urination, increased appetite and weight loss despite eating well are typical of diabetes. These signs, in conjunction with persistently high blood sugar, glucose in the urine +/- ketones. Measuring persistent hyperglycaemia (high blood sugar) can either be done using an in-house blood glucose curve, where glucose is tested at regular intervals and trended over time (this is most useful for unwell cats that are already in hospital), or via fructosamine (for well cats where glucose trends over the past 2-3 weeks). Fructosamine is often more suitable for cats as they can develop stress hyperglycaemia affecting the accuracy of results.

My cat has been diagnosed with Diabetes, what now?

There are two mainstays of treatment for diabetic cats – this includes insulin injections (for more severe cases) as well as dietary management (for all cases-some cats can go into remission with diet alone).

Administering insulin:

The most often prescribed insulin for cats is Lantus® (glargine) – which is a long-acting insulin that needs to be given EVERY 12 HOURS. Feeding must occur AT THE TIME of giving insulin – or low blood sugar may result.

Insulin MUST BE KEPT IN THE FRIDGE AND PROTECTED FROM LIGHT. Do not draw up syringes in advance as the plastic in the syringe will degrade the insulin and it may not be as effective. Ensure you dispose of needles in the sharps bin provided.

Insulin must be given SUBCUTANEOUSLY (under the skin) – the picture on the left denotes the correct way to inject insulin under the skin, ensuring not to pierce all the way through the skin

It is recommended that you SWITCH SIDES daily as seen in the photo to the left– this is the ideal site on the body to inject.

It is good to practice on something like an orange, injecting just water so that technique can be developed.


A high protein, low carbohydrate, and restricted fat diet is recommended (AKA the ‘Catkins’ diet). Your veterinarian will calculate your cat’s daily intake requirements and divide them into two meals to facilitate insulin administration. STICK TO THE DIET as any alteration or extra food can affect blood glucose (glycaemic) control.

If the cat is unwilling to eat DO NOT ADMINISTER INSULIN. If insulin is given without food, it can lead to hypoglycaemia which can potentially be dangerous. Clinical signs of hypoglycaemia include: trembling, lethargy, collapse and even seizures. If you suspect your cat is hypoglycaemic try and give them a bit of food– if your cat is unconscious, place honey or syrup on the gums (beware of bites if actively seizuring – wait for seizure activity to finish) and SEEK VETERINARY ATTENTION as intravenous glucose will likely be required. If your cat will not eat his/her meal WAIT UNTIL THE NEXT MEAL to feed and administer insulin. If they have not eaten the second meal, contact your veterinarian.

Specially formulated prescription diets are often prescribed for cats with diabetes. These include:

Royal Canin Diabetic or Hill’s M/D.

It is a good idea to keep a food and exercise diary to help communicate with your veterinarian the correlation with glycaemic control. It is also good to record how much your cat is drinking to determine resolution of clinical signs.

Long term monitoring:

Along with your diary, your veterinarian will like to do serial measurements of ongoing glucose to ensure control is adequate – this is usually done by a single blood test of fructosamine and is correlated with resolution of clinical signs.

Overall, diabetic cats can live happy lives as long as protocols are stuck to and they are regularly monitored by the veterinarian. Once diagnosed, a revisit is usually scheduled for 4-6 weeks after the initial visit: whereby the cat can be examined, diary discussed with the owner and glucose can be re-examined by the previously mentioned methods. The goal of treatment is to maintain body weight, normal appetite and reduce drinking and urinating – and potentially result in remission.