Blood glucose
Chemistry ·Also called: GLU, blood sugar, glucose serum, hyperglycaemia, hypoglycaemia
What it is
Glucose comes from digested food and from stores in the liver, and insulin moves it into cells to be used. The blood level is held within a narrow band in health, and both diabetes and its treatment disturb that balance in opposite directions.
Why your vet measures it
Persistently high glucose with sugar in the urine is how diabetes is diagnosed. Very low glucose is an emergency in its own right, causing weakness, disorientation and seizures. Both ends of the scale need acting on, but the high end needs confirming first.
What a high result can mean
- Diabetes mellitus
- Stress or excitement — extremely common in cats, and enough on its own to produce a strikingly high reading
- Steroid treatment, or Cushing's disease in dogs
- A recent meal, if the sample was not taken fasted
- Acute pancreatitis
What a low result can mean
- Too much insulin, in a diabetic pet — the most common cause and a genuine emergency
- An insulinoma, a tumour that secretes insulin
- Sepsis or severe liver disease
- Xylitol poisoning in dogs, from sugar-free gum or sweets
- Very young or toy-breed puppies with limited energy reserves
- A delay in separating the blood sample, which lets the cells consume the glucose
Dogs and cats differ
Stress hyperglycaemia is the single biggest pitfall in feline medicine — a stressed cat can read well above the diabetic threshold with no disease at all. That is why a fructosamine test, which averages glucose over two to three weeks, is usually run before a cat is diagnosed with diabetes. Dogs show far less stress-driven change.
Questions worth asking your vet
- Could stress at the appointment explain this in my cat?
- Should we run a fructosamine to check the longer-term picture?
- Was there glucose in the urine as well?
- Was my pet fasted before the sample was taken?
Related terms
See this value explained on your pet's own report
Upload the lab report or X-ray and get every value explained in the context of your own dog or cat — in minutes.
Explain my pet's results