Diabetes mellitus is a diseased state by which the body suffers from either an absolute shortage of insulin (Type I), or from an incorrect response from the cells to the insulin that is being produced, a condition termed insulin resistance (Type II). Both of these conditions will prevent the muscles and organs from converting glucose to energy, and will result in excessive amounts of glucose in the blood, which is also referred to as hyperglycemia.
An affected dog will be hungry a lot of the time, since glucose is not making it to the brain; glucose levels in the brain are too low for the brain to register that it is receiving food. Because insulin is not giving the muscles and organs the signal to convert glucose to energy, the excess glucose in the blood will be carried out of the body in urine instead of being used for energy, and there will be a concurrent lack of energy. There is also increased thirst as a result of the increase in urine. The liver is adversely affected by this condition, as are the eyes and kidneys.
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 80-120 mg/dl (4.4-6.6 mmol/L). It may rise to 250-300 mg/dl (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 400 mg/dl (22 mmol/L). Some diabetic dogs will have a glucose level as high as 700-800 mg/dl (44 mmol/L), although most will be in the range of 400-600 mg/dl (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 with a normal blood glucose level will not have glucose in the urine. Diabetic dogs, however, have excessive amounts of glucose in the blood, so it will be present in the urine. After the blood sugar reaches 180 mg/dl, the excess blood sugar is removed by the kidneys and enters the urine. This is why dogs and people with diabetes mellitus have sugar in their urine (called glucosuria) when their insulin is low.
Dogs with diabetes mellitus require one or more daily insulin injections, and almost all require some sort of dietary change. In general, they must be fed the same food in the same amount on the same schedule every day. Although the dog can go a day or so without insulin and not have a crisis, this should not be a regular occurrence; treatment should be looked upon as part of the dog’s daily routine.
Once the diabetes mellitus 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