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Energy Production-Fasting. With adequate insulin supply-endogenous or exogenous--ketones, if produced, are slight and not problematic.

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Energy Production-Untreated/Inadequately Treated Diabetes-without enough insulin to regulate fat & carbohydrate metabolism, the process intensifies. The liver, despite high blood glucose levels, produces still more in gluconeogenesis. It also speeds up the transformation of fatty acids resulting in ketones.


Hyperglycemia means high blood sugar. It is the primary symptom of diabetes. Unlike its opposite, hypoglycemia, hyperglycemia is not immediately life-threatening. This doesn't mean it's not dangerous, though. For "how high is high", see blood glucose levels, and also the long-term symptoms discussion at the end of this page.

Increasing physical activity can mean lowering blood sugar levels for some pets and people with this disease. It can also raise them; much depends on individual reaction and knowing how you or your pet responds.

For most with diabetes, excitement or stress can cause temporary hyperglycemia. There are others who can find themselves going toward hypoglycemia because of it.

Some unexpected causes of hyperglycemia are discussed in detail under regulation difficulties.

Because of the hyperglycemia Cushing's disease creates, it's possible (but not frequent) to find ketones in the urine. [1]

Primary metabolic effectsEdit

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No insulin, not enough insulin or the failure of the receptors means glucose can't get into the cells to be used as fuel. Without fuel, cells starve.

An untreated diabetic suffers primarily from lack of insulin to let nourishment into the cells, and therefore is starving to death. But hyperglycemia can kill faster than starvation; it's not unusual for one of the effects below, or diabetic ketoacidosis (DKA) brought on by the combination, to be the actual fatal blow.

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Polyuria: Glucose cannot leave the body by itself--it must take water with it. Losing too much water means the body tries replacing it and this causes thirst, or polydipsia. When too much water is lost through excess urination and the excess drinking cannot make up for it, dehydration can occur.


Hyperglycemia and glycosuria are the symptoms, or signs, that the untreated or inadequately treated diabetic is unable to metabolize carbohydrates properly. This is caused by a lack of insulin, endogenous or exogenous, in the body to assist in this process.

Depending on the severity and length of time spent in hyperglycemia, diabetics will suffer various levels of severity of symptoms, ranging from short term to long term. Almost all complications of diabetes are caused directly or indirectly by hyperglycemia [2].

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Glycosuria: When the blood glucose level rises over a certain level, the renal threshold, glucose spills into the urine.

Excess sugar in the blood is:


Vicious circlesEdit

Hyperglycemia is also at the center of several vicious circles, including:

  • Glucose toxicity [5] -- oxidized tissue becomes insulin-resistant, causing high blood sugar, which oxidizes tissues further.
  • Dehydration -- low water levels make blood sugar levels high by comparison, which makes blood hypertonic, which sucks water out of the cells into the blood. The kidneys try to cleanse the blood by filtering out the sugar along with lots of extra water, causing more dehydration.
Dehydration can change the way subcutaneous insulin is absorbed [6], causing either hyperglycemia or hypoglycemia.
Those with diabetes are at risk for dehydration as it is triggered by hyperglycemia. [7]
  • Somogyi rebound -- high blood sugar causes caregiver to increase insulin dose, which causes hypoglycemia, causing Somogyi rebound, causing high blood sugar, which causes caregiver to further increase insulin dose.
  • Dental infection -- infection raises blood sugar, making vets nervous about operating on the teeth.
  • Infections -- Untreated infection keeps blood sugar high. [8][1]

Short-term symptomsEdit

Very high blood sugar over just a few days can therefore cause:

  • Cataracts in dogs
  • High risk of ketones, and DKA
  • Neuropathy (nerve damage)
  • Dehydration
  • Malaise or lethargy
  • Urinary tract infections
  • Tissue damage everywhere due to glucose toxicity
  • Insulin resistance causing apparent unresponsiveness to insulin
  • Hyperactivity in some dogs; they become like some small children who've had far too many sweets. Our non-medical term for it is "sugar buzz".
  • Inflamation of the eye blood vessels in dogs. The whites become an angry, "fire" red. They also become inflamed as a hypoglycemia symptom, but the redness is not as intense. The difference in inflamation can best be likened to the difference in the color of arterial blood to venous blood. Arterial blood is a brighter red than venous blood. Hyperglycemic inflamation is of an "arterial blood" color.

Both revert to no inflammation when blood glucose levels are normal; lessening of inflammation visible as the bg's go down or up. This symptom was discovered and verified--first with the individual dog and then with all diabetic dogs in the veterinary practice. All presented with the same symptoms for hyperglycemia, hypoglycemia, and euglycemia. The eyes were examined prior to blood glucose testing with results matching the degree or lack of inflammation each time.

  • Similar inflammation of the eye's blood vessels noted in cats. Feline Diabetes For Dummies: [9] Watch closely and learn the signs of early HYPERglycemia. This could be PU/PD or more nebulous signs. For Darlene's cat, Pooter, one fairly reliable early sign of insufficient insulin is bloodshot eyes. Pull back the skin in front of the ear until you can see the whites of the eyes ... if there are more veins than usual, or the white part is actually pink, check the BG levels. There appear to be no recorded instances where a similar hypoglycemia effect was also noted in cats.

Although we see more mention of it when noting the symptoms of low blood glucose, it is also possible to have seizures from very high blood glucose. [10]

Medium-term symptomsEdit

Medium-high blood sugar over weeks can be nearly as bad:

Long-term symptoms and safe levelsEdit

What about the usual levels we see while regulating our dogs? Normal non-diabetic range is from 62-108 mg/dL (3.44-6 mmol/L). [11] Typical regulation ranges recommended for dogs is from 100 - 250mg/dL (5.5 - 14mmol/L). Could some higher levels be damaging?

Actual long-term effects of high blood sugar in dogs have not been well-studied, so we turn to human studies for clues. Any blood sugar level over 200mg/dL (11 mmol/L), and in more recent studies, even over 126mg/dL (7mmol/L), is considered to cause some damage in humans. A famous 10-year clinical NIH study in the US called the Diabetes Control & Complications Trial (DCCT) [12][13] (in humans) compared tightly-regulated diabetics to traditionally-regulated diabetics and their incidence of complications from diabetes. They found that the tightly-regulated patients showed:

For this reason, humans are now strongly encouraged to keep their A1C levels (similar to a fructosamine test in animals, showing an average glucose level over time) under 7%. This equates to an average plasma BG reading of 170 (9.5 mmol/L). So if human studies are any guideline, a dog should be kept at or below an average BG of about 170 / 9.5.

Stress and HyperglycemiaEdit


Stress hyperglycemiaEdit

Stress hyperglycemia (the "white coat" syndrome some pets display with visits to the veterinarian) can approach diabetic levels, and can in some instances be high enough to cause glycosuria--glucose in the urine. (Personal experience of one canine caregiver indicates a reading can be 50+ points higher, depending on whether or not the pet liked the doctor or tech doing the blood draw. [15]) Both fructosamine and glycosylated hemoglobin tests can help distinguish stress hyperglycemia from diabetic hyperglycemia when viewed in conjunction with other test results and clinical signs. [16][17]

Stress or fright causes a release of the hormone adrenalin. [18] This usually doesn't keep the blood glucose raised long enough for the renal threshold to be "crossed", sending the glucose spilling into the urine. [19]

MedicationsEdit

Some medications can produce hyperglycemia; they are listed on the Medication warnings page. I16

References Edit

  1. 1.0 1.1 Schermerhorn, Thomas (2001). pages Persistent Hyperglycemia in Dogs and Cats-pages 11. Standards of Care-Compendium.
  2. 2.0 2.1 hyperglycemia Metabolism in the Absence of Insulin. Med Bio.
  3. Rand, J., Marshall, R. (2005). Understanding Feline Diabetes Mellitus: Pathogenesis and Management page 7, Glucose Toxicity. Centre for Companion Animal Health, University of Queensland.
  4. Diabetes Mellitus. Gulf Coast Veterinary Specialists.
  5. Robertson, R. Paul (2004). Chronic Oxidative Stress in Glucose Toxicity to Beta Cells. Journal of Biological Chemistry.
  6. Pediatric Endocrine Emergency Answer Sheet. American College of Emergency Physicians.
  7. Hyperglycemia. FAQs.org.
  8. Ketosis. Novo Nordisk.
  9. Feline Diabetes for Dummies:Signs of Hyperglycemia. Feline Diabetes.com.
  10. Seizures. Washington State University.
  11. Serum Biochemical Reference Ranges. Merck Veterinary Manual.
  12. DCCT Diabetes Control & Complications Trial. National Institutes of Health.
  13. Controlling Type 1 Diabetes. Generic Health.com.
  14. 14.0 14.1 Blood Sugar and Stress. University of California.
  15. Monitoring of Blood Glucose. Animal Hospital of Pierce County.
  16. Stress Hyperglycemia. Antech Diagnostics.
  17. Crenshaw KL, Peterson ME, Heeb LA, Moroff SD, Nichols R. (1996). Serum Fructosamine Concentration as an Index of Glycemia in Cats With Diabetes Mellitus & Stress Hyperglycemia. Journal of Veterinary Internal Medicine.
  18. Variables affecting chemistry results. Cornell University.
  19. Vetsulin for Diabetic Dogs-Owners-What is Stress Hyperglycemia?. Intervet.

More InformationEdit

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