Why Is My Dog Or Cat’s Blood Glucose Level High Or Low?

Ron Hines DVM PhD

To see what normal blood and urine values are for your pet, go here

For an explanation of causes of most abnormal blood and urine tests go here

To see how tests are often grouped, go here

Glucose in your pet’s urine? Go here

Your Pet’s Blood Sugar Level = Glucose , GLU

Your pet’s blood sugar level (glucose level) needs to remain in a narrow corridor or bad things begin to happen. 

Glucose (dextrose is a form of glucose) is the primary fuel that runs your pet’s body (Fatty acids can also provide some fuel energy). Without sufficient blood glucose (=hypoglycemia), cells cannot live very long. With too much blood glucose (the common cause being diabetes mellitus) the body begins to rely on fats rather than glucose to meet its energy needs (=ketoacidosis).

If blood glucose remains high in your pet; with time, urinary tract infections, decreased disease resistance, kidney failure, nerve-related weakness (neuropathies) and eye damage can occur.

Reasons Why Your Pet’s Blood Glucose Level Could Be Too High (hyperglycemia):

Stress and excitement – especially in cats and toy dog breeds is the most common cause of a single high reading.

When your pet’s lab glucose values are repeatedly high in a non-stressed situation, diabetes mellitus and Cushing’s disease are the most common causes.

Corticosteroid tablets or injections, acute pancreatitis, IV fluids containing dextrose or a blood samples collected too soon after eating (postprandial blood sample) can all cause the glucose level to be high.

Glucose levels can be moderately elevated in dogs for up to 2 months after their last heat cycle or during pregnancy (the period that their progesterone levels are high).

Abnormally high levels of another pancreatic hormone, glucagon, due to a rare tumor called a glucagonoma has been known to raise blood sugar levels.

Kidney failure (in cat, in dog) sometimes results in high glucose levels for reasons that are unclear. The same thing occasionally happens in hyperthyroid cats.

Medications (morphine, epinephrine, thyroxin, xylazine, megesterol acetate, depopovera, beta blockers, niacin etc.) have been known to raise blood glucose levels as well.

A disease of the pituitary gland in cats (acromegaly) that produces to much growth hormone can also raise blood glucose levels.

In humans, documented reasons for elevated blood glucose levels are corticosteroid administration, the use of quinolone antibiotics, anti-psychotic medications, beta blockers, calcineuron inhibitors like cyclosporine, protease inhibitors and thiazide diuretics. These drugs might affect your dog or cat’s blood sugar level in a similar way.

Reasons Why Your Pet’s Blood Glucose Level Could Be Too Low (hypoglycemia):

The most common cause is an overdose of injectable insulin. But too much insulin (hyperinsulinism) due to pancreatic tumors (insulinomas) can have the same effect.

Addison’s disease (hypoadrenocorticism), hypothyroidism, digestion/ absorption problems (malabsorption/maldigestion), starvation and liver disease have also been known to lower blood glucose levels.

Blood sugar levels are often low in newborn, infant pets and sometimes in toy breeds with no obvious explanation.

Severe bacterial infection, misdirected liver blood flow (portosystemic shunts), severe exertion (eg hypoglycemia in lean hunting dogs) and poorly managed diabetes that has progressed to ketosis can also cause blood glucose levels in dogs and cats to be low.

Blood samples that sat too long at the lab before analysis or were collected in the wrong cap color tubes will show falsely low glucose levels.

In humans, drugs associated with low blood glucose levels are insulin injections, as well as other drugs like biguanides and sulfoureas used in the treatment of diabetes, ACE inhibitors. Beta blockers , quinolone and chloramphenicol antibiotics can cause both high and low blood glucose levels. Disopyramide, ethanol and salicylates like aspirin have also been associated with low blood glucose levels. These drugs might affect dogs and cat blood sugar levels in a similar way.

Complementary Tests:

Repeat the blood glucose test to confirm accuracy, Urine glucose determination, Blood fructosamine level, ACTH   stimulation test, amylase and specific lipase levels (cPL or fPL), blood glucose curve, glycosylated hemoglobin levels, insulin  levels,bile acids

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