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Blood glucose testing

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Maggie, a 3 year old Labrador Retriever with diabetes. The video shows Maggie having her blood glucose checked at home using one of the "lip stick" methods of testing.
Freestyle

Freestyle mini glucometer-just one of the many styles and brands on the market.


Many caregivers with diabetic pets test their pets' blood glucose at home using a glucometer. Home blood glucose monitoring is extremely beneficial for reasons of safety, better regulation and lower cost. Testing blood glucose in a dog requires a bit of practice, but those who persevere master the skill eventually.

Reasons for Home TestingEdit

Monitoring your pet's blood glucose concentration at home has many benefits and is increasingly recommended by veterinarians, especially those who specialize in diabetes. Dr. Sara Ford made a presentation about the need for home blood glucose testing at the 2010 AVMA Convention, saying, ""If you're a human diabetic you monitor your blood sugar between 4-6 times a day." I believe that state-of-the-art care in veterinary medicine in 2010 includes home blood-glucose monitoring." Dr. Ford believes testing should be done at least twice a day.[1]

SafetyEdit

Safety alone makes home blood glucose testing a worthwhile endeavor for pet owners. Just as with human diabetics, it is much safer to know an animal's current blood glucose level before injecting insulin; if the level is lower than usual, it may be appropriate to give a reduced dose in order to prevent a hypoglycemic crisis. Urine testing is not specific enough for this--either in blood glucose level or time period. [2]

Better regulationEdit

Most of the veterinary sources advocating home testing (see list below) mention the greater accuracy of tests performed in the animal's home environment compared with a hospital setting. Another advantage is that the pet can be tested frequently, which is important in trying to regulate them, but many clients do not bring in their pets for curves as often as recommended because of the cost and concern about causing distress to their pet. [3]

Less expenseEdit

Since it reduces the number of tests performed at the vet clinic, monitoring your pet's blood glucose at home lowers the cost of treating diabetes . Many companies offer glucometers for free; the greatest cost is the test strips, but this is lower than the cost of taking a pet to a vet clinic to get the necessary number of curves--which may be biweekly at first--to achieve and maintain regulation.

When to testEdit

The tests are done at least once before each insulin shot, and sometimes once more a day, about halfway between shot times, generally at the expected time of peak insulin action. While adjusting dosage, that third peak reading is vital -- the rest of the time it's just a good check once in a while. Note that the expected peak time varies by case, you'll need to determine your pet's peak time first, using some blood glucose curves. Curves are usually done on weekends or days off.

Where to testEdit

Some people think they will have to draw blood from one of the animal's veins to test the blood glucose level. This obviously isn't so. You're testing in the same manner as people with diabetes--by drawing a small amount of blood with a lancet, just as they do.

In dogs, it is most common to test:

  • The lip, inside [4] or out [5]
  • The base of the tail area [6]
  • An elbow callous on larger dogs who have them [7]
  • The paw pad [8]
  • Toenail quick [9]


Much is said (and shown in some videos) about earflap testing, [10] but most people who do blood testing seem to find more success using other areas.

There's no preferred place to test from the list above; the one that works for you and your pet is the right one for you. You may need to experiment with testing in the various spots until you find the one.

Venous vs Capillary BloodEdit

In 2002, a study was done with blood samples taken by the "ear nick" technique (drawing capillary blood for testing) and blood obtained by the traditional venipuncture method, comparing samples from both diabetic and non-diabetic cats. The non-diabetic cats' blood results with the ear nick test was not found to be significantly different from the blood testing using venous blood. For those with diabetes, the results regarding ear nick vs venipuncture was found to be significantly different, but the difference was not found to be clinically important. [11] The conclusion drawn by the study indicates that drawing capillary blood is a reasonable alternative to drawing blood from a vein. [12]

Blood glucose testing vs urine glucose testingEdit

Some reasons for preferring testing glucose levels by using blood over urine testing is that the urine used in testing may have been in the bladder for hours. Because of this, it may not be a reliable indicator of what systemic glucose levels are at the time of testing. [13] What's seen when testing urine for glucose is an average of what the level of glucose has been over a period of about 5-8 hours (the time period from last urination).[14]

Urine testing [14] also makes it more difficult to determine whether any hyperglycemia noted is the result of a Somogyi rebound pattern or a true need for an increase in insulin dosage. Urine only tests positive for glucose when the renal threshold has been exceeded for a length of time. [15]

There also must be some degree of glycosuria (glucose in urine) present in order for a urine test to detect development of hypoglycemia. [14]

With urine testing for glucose, getting a negative result means your pet is somewhere under the Renal threshold of 180 mg/dl or 10 mmol. Glucose doesn't spill into the urine until at or above that point. This could mean he/she is in the euglycemic zone where all's well or that the dog is headed for the hypoglycemic one. Knowing that the pet's blood glucose levels are too low means that you can take action with a sugar source or some food to ward off a possible hypo episode.

Factors Which Can Affect ReadingsEdit

  • Hemocrit The amount of red blood cells in the blood. Someone with higher hemocrit values will test lower than someone with normal hemocrit levels. Anyone with anemia or an anemia-related disorder will test higher than someone with normal hemocrit values. [16] If you know there is a possibility for either higher or lower than normal hemocrit values due to concurrent disease, discuss their possible impact on blood glucose readings with your health care provider.
  • Dehydration--Severe dehydration can cause inaccurate false low results. [16]
  • Fats/Lipids--Excess cholesterol or triglycerides can also produce false meter readings.
  • Other Substances can affect your test results. They include uric acid (A natural substance in the body which can be more concentrated in those with diabetes.), glutathione (an anti-oxidant known also as "GSH"), and ascorbic acid (Vitamin C). Read the information for your meter to determine what substances, if any, may affect its accuracy--discuss these concerns with your doctor.
  • Altitude, Temperature, [17][18] Humidity are all capable of having unpredictable effects on blood glucose readings. Both the meter and test strip inserts have more information about these issues. Store meter(s) and test strips according to their respective instructions.
  • Generic Test Strips are less-expensive copies of the branded ones. If and when manufacturers change anything about their meter(s) and/or branded test strips, generic manufacturers are not always advised of these changes. The type, amount(s) or concentration of the chemicals (called reagents) used in the testing process can change. Glucometers are sensitive to these changes and as a result, blood glucose readings may be inaccurate with the generic strips. [19]

Common Problems with Meters and ReadingsEdit

Why you still need Ketostix/KetodiastixEdit

While home testing blood with a meter can tell you what your pet's blood glucose levels are, most can't do blood ketone testing.

When you have high blood glucose levels, doing ketone testing with Ketodiastix or Ketostix is good practice to make sure your pet doesn't have ketones.

In a diabetic, any urinary ketones above trace, or any increase in urinary ketone level, or trace urinary ketones plus some of the symptoms of ketoacidosis, are cause to call an emergency vet immediately, at any hour of the day.

Good BG Readings but Positive Ketone ResultsEdit

When the bg readings are high enough to produce some ketones, you've taken action to bring them down and they are normal once more, it is possible to still see some positive urine ketone test results. Ketones show up in the urine right away. When you're getting normal bg readings, it means that there are no more ketones being produced. What you are seeing when you test urine for ketones and the blood glucose is in normal ranges are the "leftovers" of the ketones which were produced by the high bg episode. They will continue to show up in the urine for a while but their concentration will become less and less until they're gone. [22][23]

How to testEdit

These sites contain helpful information about hometesting with pictures and sometimes videos.


Online VideosEdit

Hometesting MisconceptionsEdit

Some vets discourage home blood testing on various pretexts. These DVMNews articles [24][14] and this Canadian Veterinary Journal (CVJ) [25] may be helpful in convincing them otherwise. Vets themselves use hand-held glucometers for a number of illness other than diabetes itself; both sepsis and insulinomas (insulin-producing tumors) cause hypoglycemia. The patients need not be diabetic to have hypoglycemia from these conditions. [26]

Vets sometimes discourage hometesting saying that it will spook the pets, making them wary of their caregivers, or could cause testing site infections. Again this turns out not to be the case. Most pets are amenable to the test once they become accustomed to the routine (petting and a treat at test time help). Concerns about test site infections can be alleviated by using hydrogen peroxide or an antibacterial ointment on the site after the test. A study [27] performed with diabetic dogs and their caregivers indicated that 85% of those new to home testing/monitoring of blood glucose were able to succeed and continue doing so with little to no problems. [28][29]

Vets also sometimes discourage hometesting saying that the caregiver will become too focused on the numbers, rather than the overall condition of the pet. While the pet's overall condition is indeed an important consideration in evaluating and treating its diabetes, blood glucose readings are critical to regulating the pet and to avoiding hypoglycemia, which is caused by injecting more insulin than the pet needs at the time.

No single blood-glucose reading, whether at a vet or at home, is adequate for determining a correct insulin dosage. The first few months can be especially tricky while finding a correct dose, and there are no substitutes for frequent testing and occasional curve-plotting. These tests are best performed at home, both because vet stress causes inaccurate readings, and because you can test more frequently and regularly at home.

Some other reasons for preferring testing glucose levels by using blood over urine testing is that the urine used in testing may have been in the bladder for hours. Because of this, it may not be a reliable indicator of what systemic glucose levels are at the time of testing. [13] What's seen when testing urine for glucose is an average of what the level of glucose has been over a period of about 5-8 hours (the time period from last urination.[14]

Urine testing [14] also makes it more difficult to determine whether any hyperglycemia noted is the result of a Somogyi rebound pattern or a true need for an increase in insulin dosage. There also must be some degree of glycosuria (glucose in urine) present in order for a urine test to detect development of hypoglycemia). [15]

You may see that blood drawn when glucose levels are normal is has a lighter color then when they are high. This is due to an enzyme (glucose oxidase) in the strip reacting to the amount of glucose in the blood. [30] I16

ReferencesEdit

  1. At-home monitoring cricial for managing diabetes in pets. American Veterinary Medical Association (26 July 2010).
  2. Dosage Adjustment-Caninsulin.com. Intervet.
  3. Cook, Audrey (1 April 2010). Identifying the reasons behind difficult-to-control diabetes in dogs. DVM 360.
  4. Inside Lip Stick. Petdiabetes.org.
  5. Outside Lip Stick. Petdiabetes.org.
  6. Tail Stick. Petdiabetes.org.
  7. Callous Stick. Petdiabetes.org.
  8. Paw Pad Stick. Petdiabetes.org.
  9. Nail Stick. Petdiabetes.org.
  10. Ear Stick. Petdiabetes.org.
  11. Thompson, M., et. al. (2001). Comparison Of Blood Glucose Values Obtained Using A Marginal Ear Vein Lance Technique Versus Peripheral Vein Collection In Normal Cats And In Cats With Diabetes Mellitus Page 25- Abstract #100.
  12. Thompson, M., et. al. (2002). Comparison of glucose concentrations in blood samples obtained with a marginal ear vein nick technique versus from a peripheral vein in healthy cats and cats with diabetes mellitus. Journal-American Veterinary Medical Association.
  13. 13.0 13.1 Blood Glucose Curves. Pet Education.com.
  14. 14.0 14.1 14.2 14.3 14.4 14.5 Levitan, Diane Monsein (2001). Glucose Testing-Blood vs Urine Tests. DVM News.
  15. 15.0 15.1 Caninsulin-Monitoring-Page 5. Intervet.
  16. 16.0 16.1 Glucometer Information-Dehydration & Inaccurate Blood Glucose Results. US Food and Drug Administration (FDA).
  17. Test Strip Temperature Ranges. Childrenwithdiabetes.
  18. Blood Glucose Meter Reference-Listing of Meter Operating Range Temperatures-. Diabeteshealth (2005).
  19. Glucometer Information- Possible Causes Of Inaccurate Blood Glucose Readings. US Food and Drug Administration (FDA).
  20. Medical Devices-Glucometers. US Food and Drug Administration (FDA).
  21. Useful Tips to Increase Accuracy and Reduce Errors in Meter Test Results. US Food and Drug Administration (FDA).
  22. Hanas, Ragnar. Insulin Dependent Diabetes in Children, Adolescents and Adults-Page 11--Important-Ketones. ChildrenWithDiabetes.
  23. Hanas, Ragnar. Urine Ketones Decrease Slowly. Children With Diabetes.
  24. Ford, Sara (2001). Capillary Blood Collection Valuable for in-Home Diabetes Management. DVM News.
  25. I. Van de Maele, N. Rogier, S. Daminet (2005). Owners' Perception Re: Home Monitoring of Blood Glucose. Canadian Veterinary Journal.
  26. Stein JE, Greco DS. (2002). Portable Blood Glucose Meters-Means of Monitoring Dogs & Cats With Diabetes Mellitus. Clinical Techniques in Small Animal Practice.
  27. Reusch, Claudia, et. al. (2003). Home monitoring of blood glucose concentration by owners of diabetic dogs. Journal of Small AnimalPractice.
  28. Schermerhorn, Thomas (2008). Strategies for monitoring diabetes mellitus in dogs. DVM 360.
  29. Casella M., Wess G., Hässig M., Reusch CE. (2003). Home monitoring of blood glucose concentration by owners of diabetic dogs-page 9. Journal of Small Animal Practice.
  30. Blood Samples for Glucose Testing Lighter-Colored When Glucose is Low. ChildrenWithDiabetes.

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