Overview of Diabetes Mellitus (DM) in Dogs
Diabetes mellitus, commonly known as “diabetes” and commonly abbreviated as “DM”, is a chronic condition in which a deficiency of the hormone insulin impairs the body’s ability to metabolize sugar. It is one of the most common endocrine (hormonal) diseases of dogs.
There are two types of diabetes mellitus in dogs. Type I DM occurs when the body does not produce enough insulin. This can be the result of destruction of the cells in the pancreas that normally produce insulin. This form does not produce enough insulin and requires insulin injections to control the disease. Type II DM occurs when enough insulin is produced but something interferes with its ability to be utilized by the body. Dogs nearly always (99%) have the type I variety.
Diabetes mellitus usually affects middle-aged to older dogs of either sex, however it is most common in female dogs (twice as common in females as in males). The peak age seen in dogs is 7 to 9 years. Juvenile-onset diabetes may occur in dogs less than 1 year of age. . Any breed can be affected. Breeds at increased risk for diabetes mellitus include the Australian terrier, Samoyed, Schnauzer (miniature and standard), Bichon frise, Cairn terrier, Keeshond, Spitz, Fox terrier and the Poodle (miniature and standard).
Diabetes mellitus leads to an inability of the tissue to utilize glucose. Disease occurs from high blood sugar levels, inadequate delivery of sugar to the tissues and changes in the body metabolism.
Risk factors for diabetes mellitus include obesity, recurring pancreatitis, Cushing’s disease, and drugs such as glucocorticoids and progestagens that antagonize insulin.
What to Watch For
Common symptoms of diabetes in dogs include:
- Increased thirst
- Increased frequency of urination
- Weight loss despite a good appetite
- Sudden blindness
- Poor body condition
Diagnosis of Diabetes Mellitus in Dogs
Veterinary care for your dog should include diagnostic tests to determine the underlying cause of the elevated blood sugar and help guide subsequent treatment recommendations. Some of these tests include:
Complete medical history and thorough physical examination.
Analysis of the urine to check for glucose and for signs of urinary tract infection.
Serum biochemical profile to determine the blood glucose concentration and to exclude other potential causes of the same symptoms.
A complete blood count (CBC).
Other tests such as abdominal X-rays or abdominal ultrasound if complications or concurrent diseases, such as pancreatitis (inflammation of the pancreas), are suspected.
Treatment of Diabetes Mellitus in Dogs
Essentially all dogs will require one or two daily injections of insulin to control blood glucose. These injections are given under the skin using a small needle. Most dogs become readily accustomed to the treatments. Your veterinarian’s office will train you in the proper use of insulin and injection techniques.
Most oral hypoglycemic agents only work if the pancreas is still producing some insulin. This is why oral medications are ineffective in dogs (because dogs almost always have type I DM).
Proper weight management, a high fiber diet and regular exercise can aid in control of DM.
Ovariohysterectomy (spaying) is indicated in female diabetic animals
to reduce the effects of estrogen on diabetes and insulin.
Complications like urinary tract infections may require additional medications, but certain drugs, including steroids (such as prednisone), should be avoided in diabetic dogs.
Prepare for frequent adjustments to therapy early in the course of treatment. Veterinarians prefer to start with a low dose of insulin initially and adjust upwards slowly to avoid overdosing. Your veterinarian may recommend hospitalization to measure the blood glucose every few hours (mapping a 24-hour glucose curve).
Glucose curves may help your veterinarian determine the best type of insulin, the dosage, and the frequency of insulin administration, however they are thought to be of limited use in some pets and are not currently being recommended for all pets.
Home Care and Prevention
At home care involves administering prescribed medications, including insulin, as recommended. Try to give insulin twice a day, 12 hours apart and at the same time each day. You should also work with your veterinarian to develop a weight management and feeding plan. Stick to regular feeding times.
Observe your dog’s thirst and frequency of urination. If these remain increased, your veterinarian may need to adjust the insulin dosage.
Insulin overdose may cause low blood glucose, potentially resulting in disorientation, weakness or seizures (convulsions). If you notice any of these symptoms in an otherwise responsive dog, offer food immediately. If the dog is unconscious, Karo® syrup can be applied to the gums. In either case, call your veterinarian as soon as possible.
Familiarize yourself with insulin, insulin syringes, insulin storage, and insulin handling; your veterinarian or pharmacist can help.
While there is no way known to prevent type I DM, proper weight management can reduce the likelihood of your dog developing type II DM.
Information In-Depth on Diabetes Mellitus in Dogs
Important symptoms of DM include increased thirst (polydipsia) and increased urination (polyuria). These are often the most prominent symptoms of diabetes mellitus, also known as sugar diabetes. Frequently there is weight loss despite a good appetite. Several other diseases can also cause increased thirst and urination. These diseases include:
Kidney failure that results in an inability to concentrate the urine
Hormone disturbances, including excess or deficient steroid hormones (hyperadrenocorticism and hypoadrenocorticism), deficient anti-diuretic hormone (diabetes insipidus or water diabetes) and excess thyroid hormone
Liver failure and certain cancers that prevent the kidneys from concentrating urine
A urinary tract infection can lead to increased frequency of urination and uncontrollable urination in inappropriate locations. Urinary tract infections often accompany DM because bacteria live well in the sugary, diluted urine.
Weight loss while having a good appetite can be observed with intestinal disease, digestive enzyme failure, kidney disease, excess thyroid hormone or cancers.
Concurrent complications and conditions often found in diabetic patients include:
Urinary tract infection due to diluted, sugar-containing urine
Infections in other parts of the body, including the gums
Acidosis (low blood pH) due to the production of ketones as the body tries to provide energy for the tissues in the absence of appropriate glucose (sugar) metabolism. Ketones are formed from fatty acids when the body believes it is starving.
Diabetic ketoacidosis, the most severe form of DM, results in severe changes in blood chemicals including imbalances in small, simple chemicals known as electrolytes.
Cataract formation because of the abnormal accumulation of sugars in the lens of the eye. Although treatment of DM will not reverse cataract formation, surgical therapies for cataracts are an option.
Pancreatitis, an inflammation of the pancreas, can occur in the same organ that makes insulin. Occasionally, severe, repeated bouts of pancreatitis can damage the organ and cause DM, but pancreatitis can also occur in animals that already have DM. Pancreatitis ranges from a mild “belly ache” to a life-threatening disorder, with vomiting being the most common clinical sign.
Hyperadrenocorticism, an excess of steroid hormones, may accompany and complicate DM in older dogs. It is not caused by DM, but left untreated it complicates the therapy of DM.
Diagnosis In-Depth of Diabetes Mellitus (DM) in Dogs
Complete medical history and physical examination. Particular attention will be given to your assessment of changes in eating and elimination activities. Changes in weight or general behavior will also be noted. The abdomen will be carefully palpated (probed by touch) to feel for changes in the size of the abdominal organs.
Analysis of the urine. This will allow your veterinarian to check for the presence of glucose or ketones (an acid produced by the body when insulin is absent), as well as for signs of urinary bladder infection, a common complication of DM.
Biochemical analysis of the blood. This test will allow confirmation of elevated blood glucose (sugar) concentrations. Elevated blood glucose is the hallmark of DM. In addition, these tests will allow some assessment of kidney and liver function and of the acidity (pH) of the blood. Results of biochemical analysis may reveal complications of DM and can often reveal the presence of concurrent diseases as well.
Blood glucose concentrations may be measured more than once. Stress, a recent meal or certain drugs may cause mild to moderate elevations in blood glucose in the absence of DM. Persistent elevations in blood glucose, particularly after a fast, often suggests DM.
Additional tests may be recommended on an individual basis. These tests include:
Glycosylated hemoglobin, the product of the cumulative effect of blood glucose on red blood cell hemoglobin, is measured by sending blood to a special laboratory. This test allows the veterinarian to get an idea of what the blood glucose concentrations are like over the course of several days instead of at one brief instant. The response of the patient to treatment must be followed.
Serum fructosamine measurements are used in the same way that glycosylated hemoglobin measurements are. Fructosamine is the product of the effect of blood sugar on the blood protein albumin. This level is generally monitored every 3 to 6 months after diabetic control is attained.
Urine culture may confirm the presence of a urinary bladder infection, prove what type of bacteria is causing the infection and tell the veterinarian which antibiotics should be effective in treating it (and which ones will not).
Complete blood count (CBC) can discover anemias (too few oxygen-carrying red blood cells), abnormal platelet numbers (too few or too many blood clotting cells) and abnormal white blood cell counts (too few or too many infection-fighting cells). Infections are a common complication of DM.
Abdominal radiographs (X-rays) may be requested to rule out changes in size of organs like the liver or kidneys or to look for evidence of abdominal tumors. Kidney disease, intestinal disease, disease of the adrenal gland or certain abdominal tumors may be present and have signs very similar to DM.
Abdominal ultrasonography uses sound waves to evaluate the contents of the abdominal cavity. A specialist often performs the test in which the fur is shaved and a probe is held against the abdomen (this is the same test given to many pregnant women to visualize the fetus). This test can reveal many of the same things as abdominal radiographs, but provides a more detailed examination along with views of the inside of organs rather than just the shadow of the organ.
Specific endocrine tests including an ACTH stimulation test, low and/or high dose dexamethasone suppression test, or urine cortisol/creatinine ratios may be requested if hyperadrenocorticism is suspected (generally in older dogs). Hyperadrenocorticism complicates both the diagnosis and treatment of DM.
If cataract surgery is anticipated, the veterinarian will likely perform an electroretinogram (electrical test of the eye) to be certain that vision will be restored once the cloudy lens is removed.
Treatment In-Depth of Diabetes Mellitus (DM) in Dogs
Treatment for diabetes may include one or more of the following:
Insulin injections are the mainstay of treatment. Essentially all dogs with DM will require one or two daily injections of insulin to replace absent or ineffective naturally occurring insulin. Most dogs require twice daily injections. These should be given as close to 12 hours a part as possible.
Because insulin is a hormone that is easily inactivated, it must be given by injection. These injections are given just under the skin using a small needle and syringe. Most pets become readily accustomed to the treatments, and despite initial trepidation, most owners can easily learn to give the injections without much objection from the pet. Type I DM, due to destruction of the pancreatic cells that produce insulin, requires life-long insulin therapy.
On the other hand, Type II DM, in which the tissues are merely resistant to the effects of insulin, can sometimes be controlled through weight management, diet changes and/or pills to lower blood glucose. Most dogs do not respond to this treatment approach as most dogs are type I diabetics.
Patients with uncomplicated diabetes are generally managed on an outpatient basis, but those experiencing complications such as diabetic ketoacidosis will require initial in-hospital stabilization.
Insulin comes from several sources and in many formulations. The most commonly available source is recombinant insulin, produced by genetically engineered bacteria to mimic human insulin. Other sources are from processed beef or pork pancreas.
Insulin formulations vary in the time they require to reach peak action and duration of action. Commonly prescribed formulations include NPH (isophane), lente, and protamine zinc (PZI). Another formulation, “regular” insulin, is very short acting and is primarily used in the hospital setting for complicated diabetics.
Diet. Proper weight management aids in control of DM. Obesity causes tissues to be resistant to the effects of insulin, while animals that are too thin do not have any energy reserves. Maintaining an optimum weight can help both type I and type II diabetics.
A high fiber diet and regular exercise can aid in control of DM. Fiber slows the absorption of carbohydrates, including sugar, from the intestine. Exercise helps improve the utilization of insulin by the tissues.
Ideally, meals should be divided into twice daily servings and offered prior to the insulin injections.
Ovariohysterectomy (spaying) is indicated in female diabetic animals. When animals come into heat (estrus), the hormonal changes alter insulin and glucose metabolism.
Drug therapy. Antibiotics may be prescribed to treat infectious complications, particularly urinary tract infections or oral (gum) infections. Certain drugs, including steroids, should be avoided in diabetics. Steroids are often used to treat skin conditions, but should be avoided in diabetics.
Animals with complications such as diabetic ketoacidosis will require in-hospital therapy, including insulin administration with frequent dose adjustment, intravenous fluids, administration of electrolytes (blood chemicals) and antibiotics.
Be prepared for frequent adjustments to therapy early in the course of treatment. Veterinarians prefer to start with a low dose of insulin initially and adjust upwards slowly to avoid overdose.
Too much insulin can be worse than not enough; insulin overdose can cause low blood glucose. When blood glucose is too low, the brain does not get adequate energy. The result can be disorientation, lethargy, seizures, coma or even death. If you notice disorientation in your alert diabetic dog, offer food immediately. If the dog is unconscious, you can apply a sugary solution like Karo® syrup to the gums. In either case, call your veterinarian immediately.
DM requires dedicated follow-up care on the part of the pet owner. With a commitment of time, education and careful observation, most diabetic dogs can have a good, quality life.
Follow-up Care for Dogs with Diabetes
Monitor blood glucose concentrations with your regular veterinarian or at home. Weekly monitoring may be needed until adequate control is attained. Serum fructosamine measurements are recommended every 3 to 6 months after diabetic control is attained.
Routine. You will need to stick with a routine in both insulin administration and feeding. While insulin does not have to be given at precisely the same time everyday, it is very helpful to stick with the same schedule as closely as possible both for drug administration and feeding.
Insulin. Familiarize yourself with the type and source of insulin your dog uses. Purchasing insulin can be confusing.
Familiarize yourself with insulin handling. This bottled hormone is not perfectly soluble or stable. It needs to be kept cool and out of direct light, and it must be gently mixed thoroughly before use, but not shaken hard.
Familiarize yourself with insulin syringes and administration. Insulin is given as “units” rather than as the standard cubic centimeter (cc) or milliliters (ml); special insulin syringes come in a variety of unit sizes. Insulin is usually administered just under the skin. Your veterinarian can spend time teaching you how to do this with a minimum of protest from your dog.
Carefully note changes in water consumption and urination. Increases in thirst or frequency of urination may indicate the need for adjustment in insulin therapy or that a complication, like a urinary tract infection, has developed. Ask your veterinarian what the expected water consumption for your dog is and periodically measure the actual consumption.
If your pet vomits or does not eat, call your veterinarian for insulin recommendations. Giving the regular dose of insulin in a pet that does not eat can cause hypoglycemia. Do not skip a dose of insulin unless recommended by your veterinarian.
Some veterinarians will ask you to catch urine samples periodically and test them at home for glucose, ketones or both. This information may help your veterinarian adjust therapy.
NOTE: A well-regulated diabetic pet should look and behave the same as a pet in good health.
Prognosis for Dogs with Diabetes Mellitus
The prognosis depends upon the overall heath of the pet, other diseases present, secondary complications from diabetes, and the pet owner’s ability to treat and closely monitor their pet’s progress. Many pets live a happy health live for years with diabetes with few complications. A mean survival time of pets with diabetes is 3 years from time of diagnosis. For pets that do well after 6 months of treatment, many will have a good quality of life for more than 5 years.