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Overview of diabetes mellitus

Diabetes mellitus is caused by an absence or reduced sensitivity to the hormone insulin. It is one of the most common endocrine (hormonal) diseases in cats.

Insulin is produced by the pancreas (an organ in the body close to the liver). This hormone controls the use of glucose (sugar) in the blood. When large amounts of glucose are in your blood, the body produces insulin which tells the body cells to "absorb" the glucose and use it for energy. This helps to maintain normal blood glucose levels and energy for normal cell functions.

When the pancreas can not produce enough insulin or body cells are unable to use insulin to transport glucose into the cells and use it for energy, blood glucose levels increase.

Diabetes in cats can be diagnosed and managed successfully in most cases, however treatment can be complex and individual cats have varied requirements. It often takes time and treatment adjustments to achieve the right balance for each cat.

Why do cats get diabetes?

Diabetes in cats is similar to type II or non-insulin dependent diabetes in humans. Abnormalities within the pancreas affect its ability to produce insulin. Additionally, body cells become less responsive to insulin (insulin resistance). These changes can be triggered by diseases as well. When these diseases are successfully treated and with diabetes treatment, some cats stop being diabetic altogether (diabetic remission).

Some drugs can induce diabetes in susceptible cats e.g. high doses of corticosteroids or progesterone-like drugs. There are other endocrine (hormonal) diseases that can cause diabetes e.g. hyperadrenocorticism or acromegaly.

Which cats are at risk of diabetes?

Diabetes tends to occur in middle-aged or older cats and very occasionally in young cats. It is more common in males and certain breeds (e.g. Burmese), however any cat can be affected. The disease is more common in overweight and inactive cats because chemicals in the fat of overweight cats can affect cell responses to insulin (insulin resistance).

Signs of diabetes

Common signs your cat may show if they are diabetic include:

Increased urine production (polyuria)
Increased thirst (polydipsia)
Weight loss
Increased appetite (polyphagia). This may not occur in all cats and some cats that become very unwell with their diabetes can stop eating altogether.

Symptoms vary in severity between cats. Other signs include:

Poor coat condition
Weakness of the back legs caused by diabetes damaging the nerves (diabetic neuropathy). This makes the cat look like they are sinking on their back legs
Liver enlargement they may develop a pot belly appearance (see here)

This cat demonstrates a diabetic neuropathy where her hocks (or ankles) are touching the ground and a pot belly appearance.

Diabetes can predispose to other problems such as bacterial urinary tract infections. Some cats may have signs such as difficulty urinating, straining or passing blood in the urine.

Some diabetic cats become very unwell and develop diabetic ketoacidosis. These cats may be extremely lethargic, collapsed and may have diarrhoea, vomiting and anorexia. It is very important to bring your cat to the vets immediately if you are worried. Diabetic ketoacidosis is a real emergency for cats.

Image above: Bacteria seen in a urine sample under the microscope.

Diagnosing diabetes mellitus in cats

Blood and urine testing is used to diagnose diabetes in cats. Diabetic cats have high glucose levels in blood and urine. Some cats can have high blood and urine glucose levels due to stress so if your cat is not showing obvious clinical signs of diabetes additional testing maybe needed to confirm the diagnosis e.g. fructosamine testing.

Fructosamine tests measure glucose bound to proteins in the blood and reflects the average blood glucose concentration over the last few weeks.

Treatment of diabetes in cats

Diabetes is not a simple disease, however it can be very rewarding to treat and cats can maintain a very good quality of life.

Diabetes treatment revolves around:

addressing predisposing factors or underlying disease
dietary management (e.g. encouraging safe weight loss in overweight cats and the use of low carbohydrate diets) and
insulin administration.

For further information on insulin see HERE

Monitoring diabetic cats

Monitoring a diabetic cat regularly is important to ensure good control of their disease. Home monitoring involves regular assessment of appetite, food and water intake and body weight measurement.

Additional monitoring may also include home urine testing (add link to performing a urine dipstick at home and obtaining a urine sample at home) and blood glucose measurements typically by using the ear tip method (add link to videos ear tip blood glucose, collecting a urine sample from your cat, performing a urine dipstick.

For Cat Specialist Services patients please find our diabetic cat diary here (enter link).

Monitoring may also be required in the hospital, such as physical examinations, body weight assessment and blood glucose, ketone and fructosamine testing. These tests help identify if the insulin dose is too little, too much or just right for your cat.

For more information see the page Monitoring your diabetic cat .

Monitoring diabetic cats with Freestyle Libre interstitial glucose monitors

Cats can be fitted with a continuous glucose monitor such as the Freestyle Libre interstitial glucose monitor. This device is used in human diabetics to measure interstitial blood glucose which is very similar in humans to blood glucose levels.

Image from Freestyle Abott

We don't know exactly how well the system aligns with cat blood glucose levels but it seems similar in most cats and can give useful data regarding trends in glucose and response to insulin.

The sensor has a small fibre which is inserted just under the skin and held in place with a small adhesive pad. Most people feel no pain when applying the sensor and they are well tolerated in most cats.

A reader is used or an smart phone application can be downloaded onto a smart phone. The results can then be downloaded or emailed.

This image shows the type of data obtained with the use of the Libre Freestyle monitor. The blue line shows the glucose level changes.

Sensors are designed for hairless human skin and most humans are unlikely to bite or scratch them off. Cats on the other hand...

It can be variable how long the sensors will work in any given patient, but typically the sensor will give data for 48 hours to 10 days. For patients requiring long term use of these sensors, they can be purchased online and applied in the hospital.

Sensors can be purchased online HERE

Prognosis of diabetes in cats

How well a diabetic cat manages in the long term depends on their age, how easy it is to control their diabetes and any other underlying diseases. Good management of diabetic cats often involves regular examinations and monitoring, both at home and in the vet clinic. With time, many diabetic cats will have a very good quality of life and some will go into remission (their diabetes goes away and they no longer require insulin injections).

If this occurs it tends to be within the first 6 months after they are diagnosed.