Insulin and Food
Elsewhere we defined “good regulation” of diabetes as the best blood sugar levels your dog can achieve safely. That is, with little risk of low blood sugar (hypoglycemia, which occurs at less than 75 mg/dL). With injections you are seeking to replace a very sensitive body system that adjusts the amount of insulin available moment by moment with an artificial system that provides a few injections of insulin a day and meals that deliver sugar into the bloodstream as they are digested.
So insulin and food are an issue of balance. Kind of like a race... a relay race really, because there is constant processing of the food and the insulin throughout the period of time between meals and injections. The finish line is the bloodstream. Sometimes the food team is ahead, sometimes the insulin.
If the insulin gets ahead of the food being digested and turned into glucose, your dog’s blood sugar can drop too far too fast. If the food gets ahead of the insulin, your dog’s blood sugar can rise too far too fast. A tie is what you want - food and insulin being delivered in balance, giving your dog a steady supply of glucose in a good range throughout the day.
This is an example of a good balance of food and insulin in a diabetic dog. The level of glucose in the bloodstream stays fairly stable and there is little difference between the highest level and the lowest level.
Keep a Daily Log
A good way to see how your dog's regulation is coming along is to keep a daily record of what and how much you fed him and how much insulin he was given in his injection. You can use a notebook, a computer spreadsheet, or a calendar to keep your notes, which will allow you to look back over time to see what worked well and what didn't and trends in your dog's blood sugar in response to his diet and insulin. You can also track other medications given, how much water she drank, what her general demeanor was... anything you think might be useful to have recorded.
Following is a brief summary of some of the key points about the insulins most often used with diabetic dogs. For detailed, comprehensive information on any kind of insulin, please see the Canines Diabetes Wiki’s insulin pages.
Dogs have tended to do best with an intermediate acting insulin. At this time, the two insulins primarily used with dogs are:
In the United States:
In Europe, UK, Australia:
Other Insulins Being Used
Some dogs have been put on glargine (Lantus) in recent years and some of them have done well using it either alone or with a faster acting insulin. But glargine’s reliability as an insulin for dogs has not been demonstrated and its use remains limited.
In 2010, with the absence of Vetsulin in the U.S. market, more veterinarians are beginning to try Levemir (Detemir) in dogs. The insulin has both potential and limitations. It can be helpful for dogs who do not get a full 12 hours from NPH. But Levemir is four times more potent in dogs – 1 unit of Levemir is approximately equal to 4 units of NPH for them – so it is problematic to give such a potent insulin to small dogs who need small doses and to dogs who are very sensitive to small dose changes. Other potential problems include overlaps if the insulin lasts longer than 12 or 24 hours. And, like all insulins, there is a tremendous amount of variation in how an individual dog absorbs the insulin and puts it to work.
NPH insulin goes by a handful of names [Canine Diabetes Wiki].
In the U.S. and Canada, it’s typically called NPH or N.
Elsewhere it is also known as Insulatard, Insuman Basal, and Humulin I.
The NPH insulin family is a genetically-engineered version of the human insulin molecule. It is an intermediate acting insulin that uses protamine, a protein from fish, to delay the absorption of the insulin so that one injection can have a measured effect on blood glucose over 8–12 hours in dogs.
As a human-type insulin molecule, this insulin differs slightly from a dog’s natural insulin. This can result in some resistance to the insulin because the dog’s body sees the insulin molecule as foreign. But that resistance can also be helpful is slowing the insulin’s absorption, allowing it to have an effect on blood glucose for a longer period of time.
NPH is generally given twice a day - an injection with a meal every 12 hours - and provides control of the dog’s blood sugar level for about 8–14 hours.
It is a very popular insulin for treating diabetic dogs as it has a very good track record of providing good blood sugar control, is less expensive than newer insulin formulations, and can be purchased without a prescription.
Walmart sells this insulin as Relion N (Walmart packages the name brand product) for significantly less.
Vetsulin / Caninsulin
Vetsulin / Caninsulin is a lente type insulin in which absorption is delayed by suspending the insulin molecule with zinc in a crystalline structure. Put very simply, the larger the crystalline structure is, the longer it takes the body to break the insulin out of that structure so it can be used. Lente insulins are intermediate acting insulins. They are a mixture of 30% semilente (a micro-sized zinc insulin crystal) and 70% ultralente (a large zinc insulin crystal). Once injected, the 30% semilente crystals are processed first and then the 70% ultralente crystals enter the bloodstream later.
This insulin molecule comes from pigs and is chemically identical to a dog’s natural insulin molecule. This typically results in no immune system reaction as the body recognizes the insulin molecule but also can make a dog more sensitive to the insulin because there is no resistance from the immune system.
NOTE: In 2010, Vetsulin was pulled from the U.S. market after an alert issued by FDA and to date, it remains unavailable in the United States. Caninsulin remains available in Canada, the UK, and Europe.
Dilution / Syringes
Vetsulin is a more dilute insulin, with 40 units of insulin in 1 milliliter of fluid (called a U-40 insulin).
NPH is more concentrated, with 100 units of insulin in 1 milliliter of fluid (called a U-100 insulin).
Syringes used for each insulin are different and the U-100 syringes used for NPH insulin are more readily available and come in a greater variety of sizes and needle gauges.
It is possible to use the U-40 Vetsulin insulin in a U-100 syringe by converting the measurement of the fluid in the syringe. Information on how to make this conversion is available here. Most often the conversion is done because the finest gauge of needle that comes on a U-40 syringe is 29 while U-100 syringes come with needles two gauges finer, 30 and 31.
It is extremely important, however, when doing the conversion to know precisely how many international units of insulin you are giving your dog so that you can communicate the number of units of insulin being given to veterinary personnel. The consequences of not understanding the difference between marks on the syringe and units of insulin can be lethal for your dog in an emergency situation.
The two dilutions are valuable for different reasons. More dilute insulins like Vetsulin are useful for small dogs who may need just a unit or two of insulin. With less insulin per drop of fluid, it is easier to measure fractions of a unit of insulin or even less than 1 unit of insulin with the U-40 Vetsulin. In large dogs, however, the more concentrated insulin means large numbers of units of insulin can be injected using a relatively small amount of fluid.
Following are links to additional good sources of information on insulin.
Limiting simple sugars and carbohydrates is an important part of matching the digestion of food with the absorption of injected insulin. Foods that are digested too quickly, as simple sugars and carbohydrates are, generally cannot be matched to a dog’s absorption of the insulin, even with faster acting insulin. The glucose from these foods speeds into the bloodstream far faster than the insulin can get there. And the result is that the dog will have very high blood sugar a few hours after eating - because the insulin hasn’t caught up - and then could have dangerously low blood sugar six or seven hours later when the food is exhausted and the insulin is getting its second wind and sprinting for the bloodstream.
For many years, a high fiber diet has been the mainstay of veterinary prescriptions for diabetic dogs. Most prescription diets for diabetic dogs are high in fiber and low in fat. In recent years that approach has been relaxed and people are finding that there are many diets that can balance the insulin’s action to give good blood glucose control throughout the day.
Click here to see a list of the various diets people are using with their diabetic dogs and the insulin that is used with them.
Nowhere is it more important to remember that every dog is different.
What works great for your dog can be a disaster for another dog.
Changing the diet is one good way to get a better balance between food and insulin and therefore better blood sugar control. Simple changes to the composition of your dog’s food will shift the speed at which that meal is converted to glucose so it can stay neck and neck with the insulin.
If you find that the diet for your diabetic dog is not giving good regulation, talk with your veterinarian about changing it to find a better balance. If you choose to change diets, home blood glucose testing is recommended as you will need to be able to monitor the effects of changes in diet.
Very general rules, which many dogs feel free to break, are:
A serial blood glucose curve is the best way to assess how well balanced your dog’s diet and insulin is.
A curve is just a series of tests of the blood glucose level, starting just before you feed and inject in the morning and continuing for as long as possible. Ideally 24 hours, preferably a minimum of 12 hours, with a test done at least every two hours.
If you learn to home test blood glucose, you can do curves yourself at home. They can also be done by your veterinarian, either by leaving your dog at the vet for the day or, if stress is an issue and you can arrange it, by taking your dog in for quick blood draws every couple of hours.
The results of a blood glucose curve where the dog has a good balance of diet and insulin look like this:
There is a small difference, approximately 100 points, between the lowest and highest blood sugar and the blood sugar never falls below 100. Keeping the blood sugar at 100 or higher allows for natural variation in blood sugar from day to day without the risk of your dog suffering from low blood sugar.
If the food and insulin are not well balanced, the curve can look something like this:
In this curve, the blood sugar falls sharply because there is more action from the insulin in the first three hours after the injection is given. The food isn't keeping up with the insulin. And then the insulin runs out (because it was used up so quickly) and the blood sugar goes high again.
Much can be done to improve problems of poorly matched food and insulin if there is someone at home every day to keep a more flexible schedule. Please check in with the forum if your diabetic dog's curves show such an imbalance.
For an example of how curves can be used to solve regulation problems, please see Chris’ case study.
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