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Diabetes mellitus is a disease of the pancreas, a small but vital organ located near the stomach. The pancreas has two significant types 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 (sugar) in the bloodstream and controls the delivery of glucose to the tissues of the body. In simple terms, diabetes mellitus is caused by the failure of the pancreas to regulate blood sugar.

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

Clinical signs of diabetes:

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

Glucose provides much of the energy needed by cells, but it must first be absorbed by the cells. Insulin attaches to the surface of cells and allows glucose molecules to leave the bloodstream and enter the cell. Without enough insulin to “open the door,” glucose is unable to get into the cells, so it accumulates in the blood, setting in motion a series of events that result in diabetes mellitus.

When this happens, the cells of the body become starved for their primary source of energy – glucose. The body then starts breaking down stores of fat and protein for energy, causing weight loss. The apparent starvation stimulates hunger and the dog eats more, resulting in weight loss in a dog 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 drinks more and more water.

Can dogs take oral medication as an alternative to insulin injections like some people do?

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

Type I diabetes mellitus (sometimes also called insulin-dependent diabetes mellitus) results from total or near-complete destruction of the insulin-producing beta cells. This is the most common type of diabetes in dogs. Dogs with this type of diabetes require insulin injections to stabilize blood sugar.

In type II diabetes mellitus (sometimes called non-insulin-dependent diabetes mellitus), there are still some insulin producing cells, but the amount of insulin produced is not enough or the tissues of the dog’s body don’t respond to it. Type II diabetes may occur in older obese dogs. People with this form can often be treated with an oral drug that stimulates the remaining functional cells to produce or release enough insulin to normalize blood sugar. Unfortunately, dogs do not respond well to these oral medications and usually need some insulin to control their disease.

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), a persistently high level of glucose in the blood, and the presence of glucose in the urine.

The body does not allow glucose into the urine until an excessive level is reached. This means that dogs with normal blood glucose levels will not have glucose in the urine. Diabetic dogs, however, have excessive amounts of glucose in the blood, so it spills into the urine. This is why dogs and people with diabetes mellitus have sugar in their urine (glucosuria) when they are not well regulated.

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

Dogs with diabetes mellitus generally require two insulin injections each day, and nutrition is an important component of disease management. In general, they must be fed the same food in the same amount on the same schedule every day. Although a dog can go a day or so without insulin without a crisis, this should not be a regular occurrence. Treatment must be looked upon as part of the dog’s daily routine. This means that you, as the dog’s owner, must make both a financial and personal commitment to treat your dog. If you must be out of town or go on vacation, your dog must receive proper treatment while you are away. Once your dog is well regulated, the treatment and maintenance costs are reasonable. The insulin and syringes are not overly expensive, but the financial commitment may be significant during the initial regulation process or if complications arise.

Initially, if your dog is so sick he has quit eating and drinking for several days, he may be in a state called diabetic ketoacidosis. This may require several days of hospitalization with intensive care. Otherwise, the initial hospitalization would be short while the dog’s initial response to insulin injections is evaluated. At that point, your dog returns home for you to administer medication. At first, regular return visits are required to monitor progress. New technology has allowed the adoption of home glucose monitoring with the use of a simple device called a glucometer. A glucometer made for animals is recommended as human glucometers are not accurate for pets. It may take a month or more to achieve good insulin regulation.

Your veterinarian will work with you to try to achieve good regulation, but some dogs are difficult to regulate. It is important to pay close attention to all instructions related to administering medication, nutrition, 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.

Once canine diabetes is properly regulated, the dog’s prognosis is good as long as treatment and monitoring are consistent. Most dogs with controlled diabetes live a good quality of life with few symptoms of disease.

Dr. Jennifer Edwards is owner of Ponemah Veterinary Hospital in Amherst, www.ponemahvet.com.