Diabetes Mellitus is a group of conditions in which there is a deficiency of the hormone insulin or insensitivity to it. Insulin is produced in the islet cells of the pancreas and is normally responsible for controlling blood concentrations of the body's main fuel, glucose. In normal animals, insulin does this by preventing glucose production by the liver and ensuring that excess glucose derived from food that is not needed for energy is put into body stores.
In a diabetic animal there is insufficient insulin to switch off glucose production by the liver or to efficiently store excess glucose derived from energy giving foods. This means that the blood concentration of glucose rises and eventually exceeds a level beyond which the kidneys let glucose leak into the urine. This loss of glucose in urine takes water with it by a process called osmosis and causes larger volumes of urine to be produced than normal. The excessive loss of water in urine is, compensated for by thirstiness and increased water consumption. The principal clinical signs of an animal with diabetes mellitus are therefore polyuria (excessive urination) and polydipsia (excessive water consumption). In addition, diabetic animals tend to lose weight because they breakdown stores of fat and protein (muscle) to make glucose and ketones (an alternative fuel) in the liver. Other clinical signs diabetics may include are cataracts, polyphagia (increased appetite), exercise intolerance and recurrent infections. If the production of ketones by the liver is excessive a condition called ketoacidosis occurs which makes the animal very unwell.
Oral hypoglycaemic are tablets used in the treatment of human diabetes mellitus, which can lower blood glucose in some cases. In general, they are not useful for the treatment of diabetes mellitus in dogs but are some use in a small proportion of diabetic cats.
Insulin is the treatment of choice for diabetes mellitus in animals. Insulin must be given by injection because it is a protein and would be digested in the intestine if it were given as a tablet. Insulin is available as pharmacological preparations for subcutaneous injection, which have been formulated to slow its absorption and prolong its action. There are three types of prolonged duration insulin preparations: lente (mixed insulin zinc suspension), isophane (NPH) and protamine zinc insulin (PZI). Of these, protamine zinc insulin has the longest duration of action and lente and isophane insulin's last long enough to be used on a once, or occasionally twice, daily basis in diabetic dogs.
There are prolonged duration insulin products available in Britain, most of Europe, Canada and Australia with licenses for treating dogs and cats (Caninsulin, Insuvet Lente and Insuvet PZI).
Insulin products have to be treated carefully. They must be thoroughly mixed prior to use and must not be frozen, heated or shaken vigorously.
Unfortunately, there is no standard dose for insulin, which can be applied to all animals. Each diabetic animal has to have its dose tailored to its individual needs, which is done over a stabilisation period. After such a period, maintenance insulin doses should remain relatively constant. In order to achieve stable control of a diabetic animal's blood glucose by insulin, all the other factors which affect blood glucose concentration must be kept constant from day to day. These factors include the composition, volume and timing of meals and the amount of exercise the animal gets.
To keep diet constant from day to day it is best to use commercially produced rather than home made diets. Certain prescription or veterinary diets can be a useful adjunct to insulin therapy such as Waltham Canine High Fibre, Hill's w/d or r/d. These diets should be avoided in underweight diabetics which need Waltham Concentration Diet, Hill's p/d or i/d. If special diets are unavailable then standard canned pet foods are acceptable.
There are a number of different ways to stabilise a diabetic animal. Some dogs are managed well with once daily injections but some will require twice daily. Some will be stabilised using blood glucose measurements taken by the veterinarian and others might be stabilised using urine glucose results. In some cases, hospitalisation is necessary and in others it is not.
After stabilisation has started the veterinarian often finds it useful to create a serial blood glucose curve by repeated measurements of blood glucose regularly throughout the day. Such a curve can be used to decide if the dog needs twice daily injections of lente or a change to PZI insulin.
The insulin treatment of cats is similar to that of dogs but requires at least twice daily injections of lente insulin or sometimes even twice daily injection of PZI because cats metabolise insulin much more rapidly than dogs.
One disadvantage to relying solely on pre-injection urine or blood glucose results is a phenomenon known as Somogyi overswing or insulin induced hyperglycaemia (high blood sugar). This is when an excessive insulin dose lowers blood glucose too far and the body responds to this potentially life threatening situation by producing hormones which are antagonistic to the effects of insulin. The release of these hormones causes blood glucose to rise again, often to very high levels, which can spill over into the urine and produce strong, positive, morning urine glucose results. If adequate care is not taken, these results can be mis-interpreted by an insulin adjustment protocol as indicating a requirement for an increase in dose. Such an increase will, in fact, only make matters worse. The possibility of inducing Somogyi overswing can be reduced by measuring urine glucose 3 times a day or by relying on nadir (lowest point in the day) blood glucose results for making insulin dose adjustments.
Dogs which are off their food or need to be fasted as part of the management of vomiting or diarrhoea need to continue to receive insulin, since withholding both food and insulin is likely to start the production of ketones and this will make the dog more unwell. Usually half of the dog's normal requirement will prevent ketoacidosis and will be safe.
There are a number of conditions, which can be associated with insulin insensitivity and therefore high insulin requirement (greater than 2 IU/kg). One of these results from insulin antagonism by progesterone in bitches that have recently been in season or which have had treatment to prevent them having seasons. Another is that caused by high levels of cortisol in diabetic dogs which also have hyperadrenocorticism (Cushings disease) or which have had repeated long acting glucocorticoid (steroid) injections. The best tests for hyperadrenocorticism are the low dexamethasone suppression test or the ACTH stimulation test but the results of these sometimes need to be interpreted with caution in diabetic dogs. Insulin insensitivity also occurs in dogs with chronic infections or chronic kidney failure.
See above. This can be associated with unusually high doses of insulin and continued clinical signs of polyuria and polydipsia, particularly in the evenings when blood glucose has been increased by the release of protective hormones.
In some dogs, even the prolonged duration insulins are used up very quickly and are no longer effective after 12 or 14 hours. This means that clinical signs will reappear in the second half of the day. This situation is best discovered by serial glucose analyses (12 - 24 hour blood glucose curve) and can be remedied by the use of twice-daily injections or a longer acting preparation.
In diabetic animals treated with insulin there is some risk that hypoglycaemia may occur. It is rare for a dog or cat to die of this condition but it is possible and owners should be appropriately warned and trained by the veterinary team responsible for their pet's management. It is most likely to happen if the animal is accidentally over-dosed with insulin, over-exercised or fails to eat its morning meal. The first noticeable clinical sign is hunger followed by lethargy and sleepiness. If untreated, stumbling and staggering ensue followed progressively by twitching, convulsions, coma and death. If the animal is still conscious, treatment is by offering food, particularly glucose containing foods such as biscuits or chocolate. If it is unable to eat, then glucose must be administered by mouth or by intravenous injection. Dissolved glucose powder or syrup will be absorbed quickly through the mucus if poured into the side of the mouth. It is not necessary for it to be swallowed. HYPOSTOP or GLUTOSE 45 are a 40% dextrose gels which are convenient to carry and easily administered orally. There are also 20 and 40% dextrose (a form of glucose) solutions available for the veterinarian to use in emergency treatment.
Ketoacidotic animals are usually collapsed dehydrated and smell of ketones (like nail varnish remover). These dogs require more intensive therapy than normal diabetic dogs and this should include intravenous fluid and special soluble insulin therapy. Often the treatment of diabetic ketoacidosis is an intensive care situation.
Information for owners of Canine's with Diabetes Mellitus
Diabetes in animals is very similar to that of humans. Therefore this page may contain links that are about humans or other animals.
Insulin Tips:
NPH cannot be mixed with any Lente (L or U) insulin, they are chemically incompatible.
Insulin does not have to be refrigerated if kept at a moderate temp, although it is recommended.
Do not give cold injections, it could cause discomfort.
Popular opinion is to dispose of opened insulin after 30 days or 100 sticks.
To prevent abscesses, infections, and discomfort, only use syringes once.
Rotation of injection sites is recommended.
It is best to feed before the injection to make sure the animal eats. (Generally 30 min. before)
Human insulins are shorter acting than animal insulins of the same type.
Never shake "cloudy" insulin. Roll the bottle between the palms of your hands.
Duration and Peak Times for the Most Common Insulins
Insulin Start Peak End Regular 30-60 min 2-3 hr 4-6 hr NPH 2-4 hr 4-10 hr 14-18 hr Lente 3-4 hr 4-12 hr 16-20 hr Ultralente 6-10 hr minimal 20-30 hr
These are only averages, each pet reacts differently to their insulin.
Caninsulin is made exclusively for animals, but is not yet available in the United States. It is currently
available in Europe, Canada and Australia from your veterinarian. Intervet is currently in the initial stages
of getting government approval for its use in the US. This product however is the same kind of insulin as
Lilly's Iletin II porcine mixed insulin zinc suspension (lente), only its more dilute for more accurate dosing in
small animals (40iu/ml instead of 100iu/ml).
Caninsulin is a lente product, and contains 30% "fast" insulin (semilente) and 70% "slow" insulin (ultralente).
PZI stands for protamine zinc insulin. This is insulin combined with large quantities of a protein called protamine. This protein slows the absorption of insulin from a subcutaneous site. These preparations have a long duration of action, but might sometimes have the problem of poor insulin absorption that also occasionally affects ultralente preps. PZI can be formulated for any species of insulin. In the UK, the veterinary licensed PZI is bovine.
How do I store my insulin?
Frequently Asked Questions About Insulin
Preparing a single dose of insulin
Preparing a mixed dose of insulin
Injecting Insulin
All About Insulin
I am often asked about the costs associated with newly diagnosed animals. There really is no simple answer to this. It depends on many things... your pet's size, the amount of insulin they require, costs of supplies in your area, how many trips to the vet you have to make, other health problems you may encounter, and so on.
Listed below are some supplies that you must have to properly care for your pet, and some that are nice to have. Check with local pharmacies in your area for the best prices on diabetic supplies.
Must have:
Nice to have:
Glucose Test Strips for Urine
Insulin
Insulin Syringes
White Corn Syrup (or other veterinary approved glucose source)
Sharps Container
Proper food prescribed by your veterinarian
Medical Alert Tag
Pet sitter with knowledge of Diabetes
Puppy Housebreaking Pads or Depends Pads
Large Syringe (without needle)
Insulin Travel Pack
Blood Glucose Meter
Insulin Protector/Case
Spare Bottle of Insulin
Please consult your veterinarian concerning your pet's particular needs. This information is general, and may not reflect levels deemed acceptable by your veterinarian.
Values above 12mmol/l (220 mg/dl) will allow glucose to leak into urine, and could cause clinical signs of hyperglycaemia if prolonged (increased drinking and urination). Many dogs run with values up to 20mmol/l (180 mg/dl) or even slighter higher for short periods of the day without any problem, so being less than 12mmol/l for the whole day may be less important than it seems at first. Signs of lethargy or "dopiness" due to high blood glucose do not appear unless blood glucose concentrations are really high (greater than 35 or 40 mmol/l) for extended periods of time.
Values below 3.5 mmol/l (65 mg/dl) might be low enough to initiate a physiological response to the hypoglycaemia and cause problems with insulin sensitivity later in the day. Because dogs in reasonable condition can mount their own defence to low blood sugar, you might not always see the classical appearance of hypoglycaemic signs.
International Readers:
To convert from mmol/l (millimoles per litre)
to mg/dl (milligrams per deciliter) the factor is 18.02