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Feline Diabetes Overview Fact Sheet

Information for pet owners on diabetes mellitus in cats.

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My cat has been diagnosed with Diabetes – what is diabetes mellitus?

Diabetes mellitus (known most frequently simply as ‘diabetes’) is a condition whereby there is a deficiency in naturally-produced insulin within the body. This can be either an ‘absolute deficiency’ (not enough insulin is produced) or a ‘relative deficiency’ (where the body does not respond adequately to the insulin available) or a combination of both. Insulin is vital for maintaining blood sugar levels within the acceptable range, and is also integral in facilitating the cells of the body to utilise blood sugar (glucose) for energy. The lack of insulin causes glucose to become dangerously high in the bloodstream, leading to it being lost into urine. High blood sugar combined with glucose in the urine are the cardinal signs of diabetes.

What are the causes and risk factors for Feline Diabetes?

Diabetes can be split into many types, with the two most common being Type I and Type II. Cats suffer almost exclusively from Type II diabetes, which is characterised by a reduction in response of the body to insulin (called insulin resistance), often alongside an inadequate amount of insulin being produced.

There are multiple risk factors for the development of feline diabetes, many of which are shared with people with Type II diabetes. These include, most notably:

  • Obesity
  • Diet and exercise routine
  • Genetics
  • Some drugs / medications (e.g. steroids)
  • Other diseases (e.g. pancreatitis, hormone diseases)

Cats who develop diabetes as a result of one or more of the above risk factors initially develop insulin resistance. Insulin’s role is to lower blood sugar levels. This is in part by stimulating glucose to be stored and in part by allowing cells to use up glucose as fuel, and so resistance to this action leads to higher blood sugar levels and to cells being starved of energy. High blood sugar then has a toxic effect on the cells in the pancreas that produce insulin, reducing the amount of insulin they can produce. This reduced insulin level causes blood sugar to increase even further and simultaneously prevents the cells of the body from accessing the energy they need. It is the combination of high blood sugar and the inability to use the available energy that causes the clinical signs we recognise in cases of diabetes.

What are the clinical signs of Feline Diabetes?

The most common clinical signs associated with diabetes are increased drinking, increased urination, a normal-to-increased appetite and weight loss. The increased urination is often profound and happens as a result of the glucose passing through the kidneys into the urine. This prevents the kidneys from retaining water normally (‘osmotic diuresis’), leading to significantly increased urine production. To prevent becoming dehydrated as a result of this, cats with diabetes therefore have to drink a lot more water to compensate for the high urine production.

Weight loss occurs as a result of the inability to use the blood glucose for energy. To compensate for not being able to use blood glucose for energy, the body has to utilise fat and protein stores, leading to breakdown and loss of both fat stores and also muscle. Cats with diabetes typically develop a reduced muscle volume, but because many cats who develop diabetes were overweight-to-obese in the first place, this can be more challenging to appreciate in some patients. In cats with severe or uncontrolled diabetes, the breakdown in fat and muscle can lead to a further syndrome called ketoacidosis which, if left untreated, will progress from vomiting, diarrhoea and severe dehydration to coma and death.

Other signs can also be seen as a result of other underlying diseases that contribute the development or worsening of diabetes. The most common of these diseases are urinary tract infections, pancreatitis (inflammation of the pancreas) and some hormone diseases, such as hyperthyroidism or Cushing’s disease.

How is diabetes in cats diagnosed?

Diagnosis of feline diabetes is generally relatively straightforward and is based on the presence of a persistently high blood sugar level, the presence of glucose in the urine, and compatible clinical signs. Blood and urine glucose can be measured easily by a veterinary surgeon.

A slight complication in the diagnosis of diabetes is that cats often show a temporary increase in blood sugar as a result of stress (referred to as ‘stress hyperglycaemia’). Generally, this is so short-lived that it does not cause measurable amounts of glucose to enter the urine, and as such the measurement of urine glucose is integral to the diagnosis to prevent a wrong diagnosis being made.

Further evidence to support the diagnosis of diabetes can be gained by demonstrating that high blood glucose is persistent by measuring it on multiple occasions, or by measuring a further parameter called fructosamine. Fructosamine acts as marker for the average blood sugar over the previous two weeks, and so would only be expected to be high in patients with persistently elevated blood glucose levels.

At the time of diagnosis of diabetes, it is also important to check further general blood parameters to screen for any of the previously discussed diseases that contribute to its development, as these may need treating at the same time as the diabetes for the treatment to be effective. If there is suspicion of other diseases, further blood tests for specific diseases (with or without x-rays of the chest and ultrasound scanning of the abdomen) may be recommended.

What is diabetic remission in cats?

In some cats, it is possible for treatment of diabetes to lead to the disease resolving. The regularity with which this occurs is variably reported and depends greatly on the intensity of management and the circumstances within which the diabetes occurred. Estimates of rates of remission vary from around 17-60% (with the lower estimates more likely to be accurate), and so, whilst remission can always be aimed for, expectations need to be tempered about the likelihood of success. Remission is considerably more likely in patients who were previously treated with drugs that cause diabetes (and which have been stopped), patients who were significantly overweight or obese and who have undergone a controlled weight loss programme, and patients whose blood glucose can be tightly controlled relatively quickly after diagnosis. Remission is also more likely in cats who will consistently eat a diabetic diet.

Remission is thought to occur because of a combination of reduced pre-disposing causes of diabetes and reversal of the toxic effects of high blood sugar on the cells in the pancreas that produce insulin, allowing return to normal production levels. In cats who begin to enter remission, insulin treatment can be gradually reduced and eventually discontinued. It is important to note that cats who have entered remission will frequently develop diabetes again in the future and so continued monitoring is required even once treatment has stopped.

What is the prognosis for cats diagnosed with diabetes mellitus?

Cats who are treated effectively for diabetes can live for very prolonged periods after diagnosis. Average length of life after diagnosis is variable dependent on which study is examined, however, average lifespans of up to around three years are reported in some studies. Considering that diabetes is more common in older cats, this length of time can often represent something approaching a normal lifespan.

Quality of life in diabetic cats is typically good to very good. A common cause of treatment failure and euthanasia is owner stress about caring for diabetic cats, including issues with care during holidays, difficulty with managing work and life commitments alongside insulin injections, and financial difficulty. It is very important to discuss any issues with management that you are having with your local vet, as there are often solutions to these issues if needed. Chasing the ‘perfect’ management of diabetes should never be at the expense of your or your cat’s quality of life and regimes can always be adapted to make them more manageable.

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