What is diabetes mellitus?

Diabetes mellitus is a disease of the pancreas. This is a small but vital organ located near the stomach. It has two significant populations of cells. One group of cells produces the enzymes necessary for proper digestion. The other group, called beta-cells, produces the hormone insulin. Insulin regulates the level of glucose in the bloodstream and controls the delivery of glucose to the tissues of the body. In simple terms, diabetes mellitus is caused the failure of the pancreas to regulate blood sugar.

The clinical signs seen in diabetes mellitus are related to the elevated concentrations of blood glucose and the inability of the body to use glucose as an energy source.

What are the clinical signs of diabetes and why do they occur?

The four main symptoms of uncomplicated diabetes mellitus are increased thirst, increased urination, weight loss and increased appetite.

Glucose is a vital substance that provides much of the energy needed by cells, and it must work inside the cells. Insulin attaches to 'receptors' on the surface of body cells and opens "pores" through the cell wall that allow glucose to leave the bloodstream and enter the cell's interior.  Without an adequate amount of insulin to "open the door," glucose is unable to get into the cells, and accumulates in the blood, setting in motion a series of events that can ultimately prove fatal.

"When there isn't enough insulin, the cells of the body become starved for their primary source of energy."

In response to this apparent starvation, the body starts breaking down stores of fat and protein for energy, causing weight loss.  The apparent starvation stimulates hunger and the dog/cat eats more; thus, we have weight loss in a dog/cat with a ravenous appetite. The body tries to eliminate the excess glucose by excreting it in the urine. Since glucose attracts water, it promotes loss of bodily fluids into the urine, resulting in the production of a large amount of urine. To avoid dehydration, the dog/cat drinks more and more water.

How common is diabetes mellitus in the cat?

"Diabetes mellitus is the second most common endocrine disease in cats."

Affecting an estimated one in four hundred cats; it is seen more frequently in middle to old-age cats and is more common in males than females. While the exact incidence is unknown, the number of diabetic cats is increasing at an alarming rate due to the tremendous increase in the number of overweight and obese cats. It is important to note that a cat three pounds over its ideal weight is considered obese. That means the average domestic cat that weighs 13 pounds or more is at high risk for developing type 2 diabetes mellitus.

Some people with diabetes take insulin shots, and others take oral medication. Is this true for dogs/cats?

In humans, there are two types of diabetes mellitus. Both types are similar in that there is a failure to regulate blood sugar, but the basic mechanisms of disease differ somewhat between the two.

"Type I Diabetes Mellitus is the most common type of diabetes in dogs." results from total or near-complete destruction of the beta-cells. This appears to be a rare type of diabetes in the cat.

Type II Diabetes Mellitus (sometimes called Non-insulin Dependent Diabetes Mellitus), is different because some insulin-producing cells remain. However, the amount of insulin produced is insufficient, there is a delayed response in secreting it, or the tissues of the dog's/cats body are relatively resistant to it (also referred to as insulin resistance). Type II diabetes may occur in older obese dogs. Dogs/cats tend not to respond well to these oral medications and usually need some insulin to control the disease. Obesity is a predisposing factor in Type II diabetes, which appears to be the most common type of diabetes in the cat.

How is diabetes mellitus diagnosed?

Diabetes mellitus is diagnosed by the presence of the typical clinical signs (excess thirst, excess urination, excess appetite, and weight loss), in addition the presence of a persistently high level of glucose in the blood stream, and the presence of glucose in the urine.

The normal level of glucose in the blood is 4.4-6.6 mmol/L. It may rise to 13.6-16.5 mmol/L following a large or high-calorie meal. However, diabetes is the only common disease that will cause the blood glucose level to rise above 22 mmol/L. Some diabetic dogs/cats will have a glucose level as high as 44 mmol/L, although most will be in the range of 22-33 mmol/L.

To conserve glucose within the body, the kidneys do not filter glucose out of the blood stream into the urine until an excessive level is reached. This means that dogs/cats with a normal blood glucose level will not have glucose in the urine. Diabetic dogs/cats, however, have excessive amounts of glucose in the blood, so it will be present in the urine. This is why pets and people with diabetes mellitus have sugar in their urine (called glucosuria) when their insulin is low.

What is the prognosis for my pet with diabetes mellitus?

Once the diabetes mellitus is properly regulated, your pets prognosis is good as long as treatment and monitoring are consistent. Most pets with controlled diabetes live a good quality of life with few symptoms of disease.

How is diabetes mellitus treated in dogs? Is treatment expensive?

"Dogs/cats with diabetes mellitus require...daily insulin injections...dietary change."

Dogs/cats with diabetes mellitus require one or more daily insulin injections, and almost all require some sort of dietary change. All cats/dogs with diabetes mellitus benefit from being fed a well-balanced diet; many pet with this disease appear to benefit from a diet that is high in protein and low in carbohydrates. A low carbohydrate diet decreases the amount of glucose absorbed from the intestinal tract and lowers the requirement for insulin.

In general, they must be fed the same food in the same amount on the same schedule every day. This means that you, as the dog's/cat’s owner, must make both a financial commitment and a personal commitment to treat your dog/cat.

It is important that you pay close attention to all instructions related to administration of medication, diet, and home monitoring. One serious complication that can arise is hypoglycemia, or low blood sugar, which can be fatal. This may occur due to inconsistencies in treatment.

"You should never change the dose of insulin without first discussing it with your veterinarian." 

What happens if my pet receives too much insulin?

"If a cat/dog receives too much insulin, it is possible for the blood sugar level to drop dangerously low."

If a cat/dog receives too much insulin, it is possible for the blood sugar level to drop dangerously low. For this reason, it is important to be very careful in ensuring your pet receives the correct dose of insulin.

The typical signs displayed by an animal with a very low blood sugar levels are weakness and lethargy, shaking, unsteadiness and even convulsions. If a diabetic pet shows any of these signs it is important to seek immediate veterinary advice or attention. In mild cases of hypoglycemia, you may observe "wobbling" or "drunken" walk or appearance and the cat may not arouse when you call or pet them. In cases of mild or early hypoglycemia, you should administer approximately a tablespoon of corn syrup, honey or sugar solution by mouth. If your pet is showing more severe signs such as ataxia or severe incoordination and unsteadiness during walking, or convulsions, you should seek immediate veterinary care. Your veterinarian can advise you on specific emergency treatment of low blood sugar in your pet.