Canine Diabetes Mellitus

Diabetes mellitus is a disease involving the pancreas. The pancreas is a small organ that lies near the stomach. It has two basic functions: (1) to produce digestive enzymes, and (2) to produce insulin. Insulin is the hormone that regulates blood glucose (or blood sugar) levels.

Diabetes mellitus occurs when the pancreas fails to produce enough insulin to control the dog's blood glucose levels. As a result, the blood glucose can become very high. Diabetic dogs require regular injections of insulin to control their blood glucose levels. Without it diabetes mellitus can be fatal.

This disease is relatively common in dogs. It is most often seen in middle-aged or older dogs. A congenital form of diabetes occurs in puppies, but it is very uncommon.

What are the signs of diabetes mellitus?

The four classic signs of diabetes mellitus in dogs are these:

• ravenous appetite
• weight loss (despite a good appetite and plenty of food)
• drinking larger than normal amounts of water
• increased urine production

These signs are all caused by low insulin and high glucose levels in the bloodstream. Glucose is a key energy source for all types of cells. However, insulin is needed in order for the glucose to be able to enter the cells from the bloodstream. (Insulin has been described as the "gatekeeper," opening the gate so that glucose can enter the cell.) When there is insufficient insulin, the cells are deprived of glucose. The body must therefore use its fat stores and muscle protein as energy sources. This process causes the dog to eat more to replenish its depleted tissues. Despite the ravenous appetite, the dog still loses weight.

Increased water intake and urine production are a direct result of the high blood glucose levels. The body tries to lower the blood glucose by excreting some glucose in the urine. However, the glucose draws water along with it, so the dog produces large amounts of dilute urine. To prevent dehydration from the water loss, the dog must drink more water.

How is diabetes mellitus diagnosed?

Diagnosis is fairly simple. It is based on three criteria:

1. the classic signs
2. high blood glucose level
3. presence of glucose in the urine

Blood glucose measurements

In a healthy dog, the normal blood glucose level is 80120 mg/dl (milligrams per deciliter). Following a meal, it may rise to 250300 mg/dl. Stress can also increase the blood glucose into this range. In a diabetic dog, the blood glucose may be well over 400 mg/dl. In fact, in some diabetic dogs the blood glucose may be as high as 800 mg/dl before treatment.

Blood glucose is measured from a blood sample. It can either be measured as part of a group of blood tests or on its own, using the same measuring kit that diabetic people use on a daily basis.

Urine glucose measurements

Glucose is not normally present in the urine. If the blood glucose level is normal, there will be no glucose in the urine. When the blood glucose level is persistently increased, glucose is excreted in the urine. This test simply requires a urine sample and a glucose test strip (dipstick).

Can diabetes mellitus be treated?

Diabetes mellitus cannot be cured, but it can be effectively managed. When the diagnosis is first made, it will be necessary for your dog to be hospitalized for a few days to get his blood glucose under control. If there are any related health problems, they must also be treated before your dog goes home. Long-term management involves the following:

• dietary changes
• daily insulin injections
• periodic monitoring

Regardless of the details of your dog's diabetes management program, consistency is essential. You must be consistent with diet, feeding times, insulin injections, and your dog's routine. Also, try to keep disruptions and stress to a minimum. You may find that it is easier to regulate your dog's routine if you keep it indoors.

What dietary changes do I need to make?

The dietary changes we recommend are:

• switch to a high-fiber diet
• diets that are high in fiber tend to be lower in sugar and are digested more slowly, so there is less of an increase in blood glucose after a meal
• we prefer Prescription Diet Canine w/d® or CNMOM®
• if your dog is overweight (despite the weight loss), we recommend Prescription Diet Canine r/d® until the ideal weight is reached
• feed your dog two meals a day, rather than free-choice (where food is available at all times)

Twice-a-day feeding is far better than free-choice feeding for diabetic dogs. It is much easier to regulate your dog's blood glucose level when you feed it twice a day. Also, it is easier for you to monitor the appetite and food intake, especially if you have other dogs.

I don't think I can give my dog an injection. Is it really necessary?

It is essential that your diabetic dog receive an insulin injection once or twice a day to control the blood glucose. On learning this, many dog owners are extremely anxious about this part of diabetes management. That's understandable. As you'll see, it is easy to do and most dogs tolerate their daily injections very well. The needle is tiny, the amount of insulin is very small, the insulin does not sting when injected, and the injection is given in an area where there is no risk of damage to vital organs. You'll quickly become comfortable with giving the injection, and your dog will consider it part of the daily routine.

Your veterinarian will show you how to draw up and give the injection before sending your dog home. Here is the basic technique:

1. Take the insulin bottle from the fridge.
2. Mix the insulin by rolling the bottle between your fingers or palms or by gently turning the bottle upside-down. Some of the insulin may have settled out while the bottle was sitting, so be sure to mix the solution thoroughly before drawing up your dog's next dose. Do not shake the bottle. Shaking causes the solution to foam, which interferes with accurate measurement of the insulin dose. Continue to roll the bottle until there is no white material in the bottom of the bottle.
3. Remove the cap from the needle and pull back on the syringe plunger to fill the syringe with air to the level of the insulin dose. Tip the bottle upside-down, insert the needle through the rubber stopper, and inject the air into the bottle. Then pull back on the syringe plunger to draw up the insulin dose. Withdraw the needle from the bottle.
4. If there is foam or air in the syringe, hold the syringe so that the needle is pointing straight up, and gently flick your middle finger against the syringe a few times. This moves any air bubbles to the highest point in the syringe. Then slowly push the syringe plunger until the air is expelled from the needle. Make sure you have the exact dose of insulin remaining in the syringe. If necessary, draw some more from the bottle.
5. Have someone hold your dog, if necessary. Gently pick up a fold of skin along your dog's back and insert the needle through the skin. Be careful not to go all the way through both sides of the skin fold, but between the two layers of skin. Angle the needle toward your dog's backbone or slightly downward. You will not cause any damage to the backbone because you have raised the skin away from the back and the needle is very short. (Use a different place on your dog's back each day.)
6. Inject the entire dose of insulin by pushing on the syringe plunger until it can go no further.
7. Remove the syringe and needle, and place the cap back on the needle right away.
8. Praise or reward your dog.
9. Put the insulin bottle back in the fridge.
10. Discard the used syringe and needle.*

(*Check with your veterinarian for proper disposal methods.)

Storing the insulin

The insulin solution we'll prescribe for your dog should be kept refrigerated (but not frozen). When it is out of the fridge, the insulin should not be left in direct sunlight. It will lose its potency if exposed to heat or direct sunlight for more than a few hours. If the solution is accidentally left on the counter top for a day, it is still usable. Get into the habit of putting it back into the fridge immediately after each injection.

Insulin is safe when used as directed. Just be sure not to inject any into yourself, and keep the bottle (and the syringes and needles) out of the reach of children.

Aren't you supposed to swab the skin before an injection?

For this type of injection, it is not necessary nor worthwhile to swab the skin with alcohol or antiseptic. Swabbing the hair or skin does not kill very many bacteria (if any). In fact, it may actually increase the number of bacteria carried with the needle through your dog's skin. Another thing to consider is that if you accidentally inject the insulin through both sides of the skin fold and onto your dog's coat, you will not know you've done it. The hair will already be wet from the alcohol or antiseptic.

Some people with diabetes take oral medication. Can't I do that with my dog?

Unfortunately not. There are two different types of diabetes mellitus in humans. One requires daily insulin injections, the other can be managed with an oral medication. Only one type of diabetes mellitus occurs in dogs. It is the type that requires daily insulin injections for control.

What does periodic monitoring involve?

Periodic monitoring is a joint venture between you and your veterinarian. You'll monitor your dog at home and schedule regular visits to your veterinarian for more detailed assessment. Periodic monitoring is important because your dog's condition and needs may change over time.

At home, you'll be monitoring your dog's:

• appetite
  • feed the same amount of food each day and check to see whether it leaves some food or seems hungry after the meal
  • body weight
  • weigh your dog at least once a month, and keep a record of its weight
  • try to use the same scales each time
• water intake and urine production
• watch for an increase in water consumption or urine production which would indicate that you dog's blood glucose is not being well regulated
• devise a way of measuring how much water is being consumed, and watch for large variations
• the average daily water intake for a healthy dog is less than 7½ oz. (225 ml) of water per 10 LB body weight (or just under 1 quart for a 40-LB dog)
• urine glucose
  • use the glucose test strips available at any pharmacy and check your dog's urine for glucose every 12 weeks
  • these strips are manufactured for use in people, but they also work well for dogs-if your dog's blood glucose is well regulated, there should be no glucose in her urine
  • if there is glucose in her urine, check her urine again the next day; call us if there is glucose in her urine two days in a row
• attitude and activity level, hypoglycemia (see below) causes tiredness and weakness

Call us if you notice a significant change in your dog's food intake, body weight, water intake, or urine production.

Should I give my dog an insulin injection on the morning of our veterinary appointment?

Timing in relation to feeding and insulin administration is important when measuring the blood glucose. To determine how well regulated your dog's blood glucose is on your current program, we'll need to know what her highest and lowest blood glucose values are on that day. The highest value will be within 30/60 minutes after she has eaten. The lowest value will be 58 hours after an insulin injection (the time of peak insulin effect). It is usually easiest for you to leave your dog with us for the day.

On the morning of your appointment, feed your dog a normal morning meal then bring it straight to the hospital. Do not give your dog any insulin until we have measured the blood glucose. If you cannot get your dog to the hospital within about 30 minutes after a meal, do not feed anything but bring the food and insulin with you. We will feed the dog, measure the blood glucose, then give the insulin injection. In either case, we'll take a second blood sample 58 hours after the morning insulin injection.

Stress can increase the blood glucose levels. So if your dog becomes excited or nervous when taken in the car or when at the veterinary hospital, it is best to drop the dog off the night before.

Fructosamine test

There is a test of blood glucose regulation that can be performed at any time, regardless of when your dog last ate or received an insulin injection. This test, called the fructosamine test, is an indicator of blood glucose regulation over the past two weeks or so. If the fructosamine level in your dog's blood is increased, it indicates poor regulation of blood glucose in the recent past.

If it is difficult for you to follow the protocol described above, this test can be useful. However, if your dog's fructosamine level is increased, it may be necessary for us to monitor her blood glucose directly. Based on the results, we will adjust her insulin dosage accordingly.

What are the signs of hypoglycemia and why does it happen?

Hypoglycemia means low blood glucose. When the blood glucose level drops, your dog will become tired and lethargic (has no energy). When it gets below 40 mg/dl, your dog may collapse and loose consciousness; he may even have seizures (convulsions). Persistent severe hypoglycemia can be life-threatening, so it is something you should be on the lookout for in your diabetic dog. It is better for the blood glucose to be too high than too low.

Hypoglycemia in a diabetic dog occurs because the insulin dose given is too high for the dog's needs. Here are some situations in which this could occur:

• your dog's insulin requirements have changed, yet the same dose is given
  • most dogs do fine for months or years on the same insulin dose, but it is possible for a dog's insulin requirements to change over time
  • this is why daily home monitoring and periodic veterinary monitoring are important
  • your dog didn't eat all of his meal, yet the same insulin dose was given
  • if your dog did not eat his meal, skip that insulin injection; if he ate only half of his meal, give only half of his regular insulin dose
• more than the prescribed dose was given
  • this can happen if you are not careful when drawing up the insulin dose
  • it can also happen if your dog is given two doses (e.g. you forgot that you'd already given it and you gave it again, or someone else in your home also gave it)

To prevent double-dosing or missing a dose, make a chart to record your dog's daily insulin injections. Tick off the chart after each dose is given.

What should I do if I think my dog is hypoglycemic?

No treatment may be necessary if your dog is just a little tired and lethargic. The blood glucose will gradually rise over the next few hours as the effects of the insulin wear off. If your dog is slow to return to normal or if it is very lethargic or depressed, give a tablespoon of corn syrup by mouth. Wait 15 minutes; if there is no response, give him another tablespoon of corn syrup. If there is still no improvement, or if he is unresponsive or having seizures, call our hospital immediately. Dogs with severe hypoglycemia must be treated with intravenous glucose as soon as possible.

If you cannot identify a reason for your dog's hypoglycemic episode, bring him to the hospital for evaluation. Even if the hypoglycemia was mild and resolved on its own, it suggests that we may need to revise his program.

This all seems overwhelming now. Is it really worth it?

Only you can decide that. It is true that long-term care of a diabetic dog requires considerable commitment on your part. Your dog's diet and routine must be kept consistent, and it must receive an insulin injection once or twice a day for life. If you are going away, you'll need to make arrangements for someone reliable to take over your dog's care until you return.

The good news is that the special diet, insulin, and supplies (syringes, needles, urine dipsticks, etc.) are inexpensive. The initial testing and getting your dog's blood glucose under control may be expensive if there are complications of the diabetes or other health problems. After the initial few days of hospitalization, you will need to bring your dog back in for monitoring every 7 days until we achieve good regulation of her blood glucose. After that, periodic evaluations are necessary. The cost of long-term maintenance is low.

by William M. Fraser, D.V.M.

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