Diabetes in Cats

diabetes in cats

Diabetes mellitus (sugar diabetes/DM) is a common endocrine disorder in cats. There are two types of diabetes, type 1 — in which the pancreas doesn’t produce enough insulin — or type 2 — in which the body’s cells don’t respond appropriately to insulin. Most cats have type 2 diabetes.

Type I diabetes – Cells of the immune system attack and destroy islet cells which result in a decreased number of cells producing insulin.

Type II diabetes – Cells build up a resistance to insulin (known as insulin resistance) and despite the pancreas producing enough insulin, it is unable to unlock the cells as efficiently.

Insulin is a hormone produced by the pancreatic islet cells. When a cat eats, food is broken down into organic compounds in the small intestine, one of which is glucose. Glucose is taken up by the cells for energy, growth, and repair. As glucose enters the bloodstream, the pancreas matches it with the correct amount of insulin. Insulin is required to enable glucose to enter the cells, acting as a key to unlock it. When insulin arrives at the cell, it stimulates the cell to activate glucose transporters, pulling the glucose through the wall of the cell.  When the cells don’t have enough glucose either because there isn’t enough insulin or the body resists it, they lack the energy required to enable the cat’s body to work properly.

What is the normal blood sugar level in cats?

Normal levels range from 70 – 150mg/dL (US) or 3.85 – 8.25mmol/L

Which are cats at risk of feline diabetes?

Diabetes most commonly affects middle-aged to older cats with a mean age of 7 years. The disease has an incidence of between 0.4% and 2%. One Swedish report found that males had twice the incidence of diabetes than females.

What are the effects of diabetes on the cat?
  • High blood glucose levels – Glucose builds up in the bloodstream (high blood sugar), this is known as hyperglycemia.
  • Weight loss – Because the glucose is unable to enter the cells, the body is starved of energy and the cat processes fat stores and muscles for energy, the cat begins to lose weight, despite having a healthy appetite.
  • Diabetic ketoacidosis (DKA) – If diabetes goes untreated, the body will begin to break down its own fat to use as energy. Ketones in the blood are a by-product of the body’s digestion of its own tissues and is a serious condition. As ketones accumulate in the blood, it becomes too acidic.  Ketones in blood or urine are a sign the disease has progressed which requires immediate veterinary attention. Symptoms of ketoacidosis include loss of appetite, lethargy, vomiting, diarrhea,  breath which has a sweet/fruity smell, slow respiration, dehydration, weakness and eventually coma. This is a medical emergency and requires urgent veterinary intervention.
  • Increased urination and thirst – The kidneys try to remove the glucose from the blood, and high levels of urine are produced, which causes excess thirst in the cat. This is known as polydipsia (PD). Due to the higher workload placed on the kidneys, they are often the first organs to show signs of damage.
  • Retinopathy – High blood sugar also has a damaging effect on the tiny blood vessels which nourish the retina. This is known as diabetic retinopathy and can cause sight issues from the range of mild vision problems to complete blindness.
  • Neuropathy – Nerve cells are also susceptible to high glucose levels in the blood as the nerve, eye, and kidney cells do not require insulin to take up glucose, so in the diabetic cat, they may take in high levels of glucose from the blood leading to neural toxicity. The hind legs are most commonly affected. Early signs of neuropathy in your cat’s hind legs include walking on the hocks, weakness which may make it difficult for your cat to jump, left untreated the condition can progress to paralysis. Gastroparesis is an inability of the stomach to empty itself of food due to damage to the vagus nerve which signals the stomach to contract. Once this nerve becomes damaged, it is no longer able to perform this function properly.
  • Diabetic nephropathy (diabetic kidney disease) – This rare condition occurs as a result of damage to the glomeruli, which are tiny filtering units in the kidneys due to high blood glucose levels.
  • Immunosuppression – Diabetes weakens the cat’s immune system, leading to greater susceptibility to infections and slow wound healing due to a delayed response as well as impaired function of the immune cells.
  • Urinary tract infections – These are more common in diabetic cats due to increased amounts of glucose in the urine which provide a favourable environment for the growth of bacteria. Symptoms of urinary tract infections include frequent urination, painful urination and often urinating outside the litter tray.

The earlier diabetes is detected, the less time the disease has had to damage the cat’s body, so it is important to seek veterinary attention as soon as you see any changes in your cat. Some of these conditions can be treated and/or reversed if caught early.

What are the symptoms of feline diabetes?

There are many symptoms of diabetes, depending on the severity and length of time your cat has been a diabetic, you may not see all of these symptoms. The main four symptoms of feline diabetes are increased thirst, urination and appetite and weight loss.

  1. Increased urination (polyuria) – Hyperglycemia (high blood glucose) and ketoacidosis lead to increased urine output as the kidneys remove excess glucose and ketones from the blood via the urine.  Ketoacidosis develops when the body looks for alternate sources of fuel and breaks down fat (and muscle) for energy. The breakdown of fat produces waste products called ketones, which are removed from the body via increased urine production.
  2. Increased thirst (polydipsia) – The increase in urination leads to excess water loss, so your cat tries to compensate by drinking more water.
  3. Increased appetite (polyphagia) – Because the glucose isn’t able to reach the cells to provide the energy the body tries to refuel by eating more food.
  4. Weight loss – Despite an increased appetite, your cat loses weight as his body starts to use fat and muscle as an alternate energy source.

In addition to the four classic signs of diabetes, diabetic cats may also experience the following symptoms:

  • Vomiting – Diabetes can cause vomiting in a number of ways. Hyperglycemia or low blood sugar levels (hypoglycemia),  gastroparesis and Ketoacidosis can all cause nausea in diabetic cats.
  • Weakness in hind legs – Neuropathy can affect the nerves of the hind legs due to increased blood glucose levels. Weakness can develop and left untreated can progress to paralysis.
  • Fruity smelling breath – In cats who develop ketoacidosis, a by-product of fat metabolism is acetone, which is responsible for the sweet, fruity smell on the breath.
  • Dehydration – Due to the increase in urination caused by the kidneys trying to remove excess glucose from the blood.
  • Poor coat condition (dry/dull coat, dandruff).

It is important to always be observant of your cat’s general wellbeing, eating, and toileting habits; if you see anything out of the ordinary, seek veterinary advice as soon as possible.

What causes feline diabetes?

There are several reasons a cat may become diabetic.

Obesity is the most common cause of diabetes in cats,  sadly more and more cats are becoming overweight.  What is now known is that fat is an important endocrine organ, that is, it secretes a number of hormones (adiponectin, resistin and leptin) and cytokines (cell signalling proteins) which control the regulation of insulin. These are collectively known as ‘adipokines’

Genetic predisposition can cause insulin resistance (type 1 diabetes is more commonly seen). Burmese cats in Australia, New Zealand and the United Kingdom have a higher incidence of type II diabetes.

Cushing’s syndrome causes elevated blood sugar levels, which can lead to secondary diabetes.

Pancreatitis results in the destruction of pancreatic cells, leading to a decreased number of cells able to produce insulin. Some medications (steroids) can also play a role in the development of diabetes.

Acromegaly is a rare endocrine disorder in cats caused by a benign but functional tumour of the pituitary gland which secretes excess levels of Growth Hormone (GH). Increased GH in the blood causes the body to produce too much insulin-like growth factor-1 which can affect how the cat processes glucose.

How is feline diabetes diagnosed?

A tentative diagnosis may be made based on presenting symptoms. A physical examination from your vet may indicate diabetes such as enlarged liver (hepatomegaly) due to lipid accumulation, weight loss, poor coat condition, and dehydration can all point to diabetes (but may be caused by other diseases also).

  • Your veterinarian will perform routine screening tests such as complete blood count, biochemical profile, and urinalysis. Hyperglycemia (increased blood sugar levels) and glucosuria (increased sugar levels in the urine) may be revealed if your cat is diabetic. Ketonuria (ketones in the urine) may also show up in the urinalysis. The presence of ketones in the urine indicates that the disease has progressed.
  • Biochemical profile results may reveal hypokalemia (low blood potassium levels) and hypophosphatemia (low phosphate levels).
  • Measuring levels of fructosamine in the blood is another method to test for diabetes. Fructosamine is formed when albumin (a blood serum protein) and glucose bond together; this measurement gives an idea of average blood glucose over the preceding two to three weeks. Reduced total protein and hyperthyroidism can cause a decrease in the result. Chronic stress can cause a small increase, but not usually in the same range as diabetes.

Diagnosis based on a single blood test may prove inaccurate as it is possible for the blood to show elevated glucose levels as a result of stress (known as transient hyperglycemia). Therefore a diagnosis based on a single blood and/or urine test cannot give a definite diagnosis of diabetes. There are several solutions to this. Perform several blood and urine tests over time. Try to collect a urine sample from home, when the cat is not stressed.

How is feline diabetes treated?

There are many possible regimes for the diabetic cat, depending on the severity of the disease. The primary goal is to keep blood glucose levels under control. This can be a fine balancing act which requires careful monitoring to ensure levels don’t become too high or too low. It can take several weeks for your cat’s blood glucose levels to become stable.

Type 1 diabetes requires daily insulin injections.

Type 2 diabetes is treated with dietary management, reducing obesity and if necessary, daily insulin injections.

Dietary modification: In mild cases, the cat may be managed with diet alone. If the cat is not ill and has no ketones, it may be possible to manage diabetes without the use of insulin. A great deal of focus is now being placed on feeding a high protein and low carbohydrate diet by switching from dry food, which is high in carbs, to canned food or home-prepared diets. Cats in the wild mostly consume protein in their diet, however, most modern pet foods (especially dry foods) contain between 30-70% carbohydrates. In fact, some cats have had their diabetes reversed by switching to a low-carbohydrate diet. This is known as diabetic remission. Commercial diets suitable for diabetic cats include Hills M/D, Royal Canin Veterinary Diet Diabetic and Purina DM. These come in canned or dry form, canned is always preferable.

Weight control: This may careful weight loss under the supervision of your veterinarian if your cat is obese or increasing calories/switching to a high-calorie diet in cats who have lost weight due to uncontrolled diabetes.

Increase exercise: Another way to help an overweight cat lose weight is to schedule daily play sessions. All it takes is 10-15 minutes twice a day.

Medications: Oral hypoglycemic drugs (such as Glipizide) may be prescribed to lower blood glucose. The exact mechanism of glipizide isn’t known, but it is believed that it stimulates the pancreas to release insulin. This treatment is only effective if the pancreas is still producing some insulin. Your veterinarian will regularly monitor your cat’s blood glucose levels (or ask you to), and if they can not be managed with medications, the next step will be insulin injections.

Insulin: This involves the injection of insulin once or twice a day. It is administered subcutaneously (under the skin) at the scruff of the neck. These can be given at home, usually at regular, daily times. Individual cats respond differently to insulin, and doses may need to be adjusted based on blood glucose profiles, clinical response, and urine glucose monitoring. Insulin comes in different forms, short-acting, intermediate-acting and long-acting. Most cats will be put on intermediate or long-acting insulin. One person in the house should be in charge of administering insulin which reduces the chances of either a missed dose or a double dose which can be life threatening (see below). If you are ever in doubt as to whether your cat has received his dose of insulin, it is far safer for him to skip a dose than run the risk of him having a second dose. Insulin must always be given with food, usually twice a day and 12 hours apart although some cats may be given insulin once a day. Your veterinarian should provide you with a print out of insulin dosage and times as well as how often to feed. Never administer insulin without a meal as it will result in low blood sugar.

  • Hypoglycemia (low blood sugar) is a potentially life-threatening complication of insulin therapy. This is caused by either too much insulin, administration of insulin without food or the cat not eating enough. The cat’s blood sugar levels dip dangerously low. Careful monitoring of your cat’s blood sugar levels is important. Signs of hypoglycemia include weakness, listlessness, lethargy, wobbly gait, convulsions, and coma. If left untreated, it can lead to death. If you notice any of these signs in the diabetic cat, you should offer it some food to eat. If this is not possible, rub a tablespoon of corn syrup onto his gums. Do NOT force fluid or liquids down the mouth, and keep your fingers be placed inside the mouth of a cat having convulsions or in a comatose state. You should notify your veterinarian immediately so that the insulin dose can be readjusted.
  • Storing and handling insulin. Bottles which are currently in use can be stored at room temperature which is more comfortable when injected. Opened bottles last for 28 days, to help keep track, write the ‘opened date’ on the bottle. Insulin should be kept out of direct sunlight. Unopened bottles should be stored in the refrigerator. Never use bottles which have been opened longer than 28 days and discard any insulin if the use by date has expired. Only ever store it in the refrigerator, insulin loses its potency when frozen.

Regular monitoring and testing: Even though diabetes may be mild, careful monitoring of the cat is vital, particularly in the early days after diagnosis. Blood and urine glucose testing may be carried out at home if the owner is confident, or at the veterinary practice. Testing is performed in much the same way as with diabetic people. A pin prick allows for a small drop of blood to be tested with a blood glucose monitor which will quickly give a reading of your cat’s glucose levels. In addition to that, your veterinarian may want you to test your cat’s urine for the presence of ketones and glucose. A non-absorbant cat litter can make acquiring a urine sample easier, a ‘test strip‘ is then dipped into the cat’s urine and will provide a reading. Your veterinarian will provide you with baseline levels, and if during testing your cat’s urine or blood sugar levels are elevated, contact your veterinarian immediately.

In addition to monitoring your cat’s blood and urine, it will be important to pay close attention to his food and water consumption as well as urine output. To measure your cat’s water intake, fill a measuring jug with water and put into your cat’s water bowl. The following morning pour the remaining water back into the jug which will enable you to calculate you how much water your cat has consumed in the past 24 hours.

Your cat should also have his weight checked weekly. A pediatric scale is the best for this.

It is highly recommended you purchase a book and log all of your cat’s test results such as blood and urine glucose levels, weight, amount of food and water consumed as well as symptoms such as vomiting your cat may experience.  This can help you and your veterinarian monitor your cat’s progress and if necessary, make changes to his treatment.

GLP-1 Analogues are a new way of treating diabetes in humans which will hopefully be able to be used in cats some time in the future. Glucagon-like peptide (GLP)-1 is a hormone secreted by the gastrointestinal tract after eating which stimulates the secretion of insulin as blood sugar levels rise. These medications reduce the level of glucose in the blood by increasing the amount of insulin. The benefit of this medication is that it only works if blood sugar levels are high. Ohio State University has begun studying the effects of these drugs on cats. Another potential benefit is that administration may only be necessary once a month.

Obviously, if there is a concurrent disease such as acromegaly, Cushing’s Syndrome or pancreatitis, these will also need to be treated.

What is the prognosis for cats with feline diabetes?

If properly managed, a diabetic cat can live for many years. In some cases, diabetes has resolved itself, in time. It is important to regularly monitor your cat and work closely with your veterinarian.

Preventing diabetes in cats:

As obesity plays such an important role in the development of diabetes, controlling his weight is extremely important. Obesity is defined as anything over 20% his optimal weight.

Re-thinking what we feed our cats is also high on the agenda. For years now, cats have been fed high carbohydrate dry food which contributes to the obesity epidemic we are now seeing. A much better option for cats is either canned or a raw based diet.

Regular veterinary appointments are also important. A cat should see a veterinarian for a health check at least once a year, and cats over seven should visit twice a year. While this may not prevent diabetes, the earlier it is found, the better the outcome.

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