Feline Diabetes

by Dr. Francesca Brown

What is it?

When we use the term 'diabetes' in cats we are usually referring to the condition ‘Diabetes Mellitis’ or ‘sugar’ diabetes. This is where the cat has a problem controlling its blood sugar levels and they are too high in the blood stream.

Diabetes is relatively common in cats, but unlike dogs where most diabetes requires the injection of insulin for life, depending on the type of sugar diabetes they have, cats may not always require insulin to control the disease for life.

Like humans, there are 2 types of sugar diabetes:

  • Type 1 – The pancreas does not produce enough insulin. This type requires the injection of insulin to control it.
  • Type 2 – The body’s cells don’t respond correctly to the insulin that is produced. With Type 2 diabetes, insulin is not always required to control the disease.


Image source wikimedia commons


Why does the body need insulin?

Insulin, produced by the pancreas, is required to control the level of sugar (glucose) in the blood of animals (or humans for that matter).

When a cat eats, food is broken down and absorbed through the wall of the intestines. The breakdown products of food include glucose. Glucose is required by all the body’s cells to provide energy so they can continue to grow and repair themselves. In a normal cat, the pancreas produces just the right amount of insulin to enable the blood glucose to be absorbed into the body’s cells.

If the cat has diabetes, the glucose is not absorbed into the body cells, so they are unable to use the glucose. The glucose then accumulates in the blood stream and the cat develops hyperglycaemia which means the level of glucose or sugar in the blood is too high. Glucose may soon be seen in the urine as the excess levels in the blood stream are filtered through the kidneys.


Why is high blood sugar a problem?


Effect on body cells

If the body’s cells are unable to get the supply of glucose they need, the body cells are starved of energy. The consequence of that is the cat begins to lose weight despite having a normal (or in many cases excessive) appetite. If the diabetes continues uncontrolled, the body begins to break down the fat and protein to use for energy which leads to further weight loss.

The breakdown products of fat and protein result in increased levels of ketones. These then start to be seen in blood in urine tests and are a sign of further progression of the disease. Ketones result in a condition called ketoacidosis which is a serious consequence of the disease and requires immediate veterinary attention. The body’s cells are also unable to reproduce, so in tissues where cells are replacing all the time, such as skin, the number of cells reduces causing serious problems to the integrity of that organ.


Effect on kidneys

As well as ravenous appetite, the cats also have increased requirement for water. This is known as polydipsia and occurs when the kidneys filter glucose into the urine, taking excess water with it because of osmotic pressure. This also creates a high workload for the kidneys and in uncontrolled diabetic cats, the kidneys are often the first organ to show signs of damage.


Effect on blood vessels

High blood sugar is damaging to the blood vessels. The smallest blood vessels in the eyes are the first to show signs. The condition is known as diabetic retinopathy and can lead to problems with sight, ranging from mild sight deficits to complete blindness.


Effect on nerves

Diabetes also has a significant effect on the nerve cells. Diabetics can have weakness in the legs (known as a neuropathy). Nerve, eye and kidney cells do not require insulin to take up glucose in the diabetic cat so make take in higher than normal levels of glucose.

The earlier diabetes is picked up, the less damage occurs to the cats organs and therefore the better the chance of maintaining the cats quality of life. If you notice any changes in your cat, no matter how mild, contact your veterinarian for advice.


What signs might I see if my cat had diabetes?

  • Any cat is at risk of developing diabetes, but is is more commonly seen in middle aged, overweight male cats.
  • Increased appetite Increased urination
  • Increased drinking
  • Weight loss – note that many diabetic cats develop the condition because they are overweight. Uncontrolled weight loss in overweight cats has serious medical implications for your cat without the presence of diabetes complicating things.  Uncontrolled weight loss in an overweight cat requires urgent medical attention.
  • Vomiting
  • Weakness in the limbs – especially the hind legs
  • Bad breath – cats with diabetes, especially where it has been present for a while, can start smelling like ketones (for those of you that remember that smell from school chemistry labs!). This is a sign of progressed diabetes and requires urgent medical attention.
  • Smelly breath should always result in a trip to the veterinarian. Diabetes, kidney failure and poor teeth are 3 common and serious conditions that cause bad breath in cats and need prompt veterinary attention.

Not all these symptoms listed above will be seen, especially in early diabetes. Any one of these signs can be a signal of a serious problem for your cat and you should seek veterinary attention.


What is the cause of diabetes in cats?

There is no specific cause yet recorded in cats. However it is likely to be a combination of factors including genetic predisposition – i.e., the cat has inherited a gene that predisposes them to diabetes; obesity – this can cause resistance to insulin (type 2 diabetes); the presence of other disease such as pancreatitis (inflammation of the pancreas); and hyperthyroidism may play a role, as may some medications such as steroids.



Diagnosis requires a visit to one of our veterinarians. They will ask you lots of questions and examine your cat. They may find things such as an enlarged liver (due to increased fats in the liver from breakdown of body tissues), weight loss, poor coat condition and dehydration. As well as a number of other diseases these may be an indication of diabetes.

Our veterinarian will then usually order a blood test and urine sample. In order to confirm diagnosis of diabetes in a cat, several blood tests over time may be required due to the risk of a cat producing a stress hyperglycaemia (increase blood glucose) result, or they may use a test that measures fructosamine levels which give an indication of the blood glucose level of the last 1 - 2 weeks.

There are other things our veterinarians will look for in the blood tests too, to support the diagnosis and ensure that there are no other underlying problems.



Once a diagnosis has been made, treatment in cats will depend on the severity of the disease.

In mild cases where the cat is not ill and has no signs of ketones, diabetes may be able to be managed without the use of insulin. It usually involves a combination of dietary modification and weight loss. In addition, our veterinarian may prescribe oral hypoglycaemic medications which help to stimulate the pancreas to release insulin (one such drug is Glipizide). This should be done alongside careful monitoring by our veterinarian. They will ensure that the cat is stable or improving. If there are any signs of deterioration, insulin may then need to be added to the regime.

In sick diabetics, as well as dietary modification and weight loss, insulin will be used. It requires an injection under the skin of minute quantities of insulin. These can be given at home, after careful training from one of our veterinarians or veterinary nurses.

Training is required in:

  • giving the injection
  • care of the insulin and the syringes and needles
  • signs to monitor and timing of injections and feeding.

However the process can be easily learnt and clients quickly become confident and competent in the task.

Levels of insulin injected may need adjusting from time to time. This involves regular blood glucose testing (usually a glucose curve completed over a 24 hour period), urine glucose monitoring and monitoring the clinical signs displayed by the cat.


Potential problems

Low blood sugar or hypoglycaemia is a potentially dangerous complication of diabetes, when the cat receives more insulin that it requires or the cat is not eating enough. The body absorbs too much glucose from the blood stream into the cells causing the blood to lack glucose. When this happens, the cat can be weak, listless and lethargic, wobbly and may progress to tremors, seizures and then coma.

Feeding small but frequent meals will help to avoid this condition, but if you do notice any of these signs, try and offer the cat food. If it refuses or it is already heading towards a seizure, make up some glucose syrup and place small amounts onto its gums. Don’t force fluids down its mouth as it may aspirate these into its lungs if it is unable to swallow properly, which is often the case in a cat in hypoglycaemic shock.

Notify us immediately of the problem so the cats medications can be reviewed. They may also need immediate veterinary treatment for the hypoglycaemia if you are unable to return the cat quickly to consciousness.


How long will my cat live with diabetes?

Provided you have sought veterinary treatment and you have now got your cat properly managed for the diabetes, these controlled diabetic cats can often live for many years. In a few cases the diabetes will resolve itself over time with proper weight management and diet.

With any diabetic cat regular monitoring by your veterinarian is an essential part of treatment and control.   


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