Glucose in cats and dogs
Glucose is the main sugar in the blood and the body’s quickest fuel. On a lab form it shows the level at the moment the sample was taken — and in cats that moment matters a lot: the stress of a clinic visit alone can raise glucose well above the reference range. One high result is a reason to look further, not a diagnosis.
What it shows
Glucose comes from food and from the liver, which stores it and makes new glucose between meals. Insulin from the pancreas moves glucose into cells; stress hormones such as adrenaline and cortisol push it up. The number on the form is a snapshot of this balance at one moment.
A snapshot is easily moved by what happens around the blood draw. Fear releases adrenaline, which raises glucose for a few hours; a meal raises it mildly. And if serum or plasma is not separated from the blood cells promptly, the cells keep using the sugar in the tube and the result comes out falsely low. For the previous weeks rather than one moment, vets use fructosamine.
Higher than reference — what it may be a sign of
- Stress hyperglycemia: fear, handling and the clinic visit itself. In cats it can be pronounced — eClinPath gives around 300–400 mg/dL (about 17–22 mmol/L) as an example — while dogs usually stay below 300 mg/dL. The adrenaline-driven rise is transient, lasting about 4–6 hours.
- Diabetes mellitus: glucose stays high and spills into the urine. Merck notes that the diagnosis rests on persistent hyperglycemia together with glucose in the urine, not on a single value.
- Cortisol and steroid medicines: they give a more sustained rise that can last several days.
- A recent meal: a mild rise for several hours after eating.
Lower than reference
A low result is first checked against sample handling: when serum is left on the cells, for example blood sent to the lab on the clot, glucose keeps falling in the tube. Real causes include insulin-secreting tumours (insulinoma), sepsis, severe liver failure (eClinPath notes that more than 70% of functional liver mass must be lost first), Addison’s disease (hypoadrenocorticism), juvenile hypoglycemia in toy and small-breed puppies, and hunting dogs whose energy demand exceeds supply. Xylitol, a sweetener in some human foods, stimulates insulin release and can lower glucose within about 30 minutes. Weakness, wobbliness or seizures with low blood sugar need a vet straight away.
Look at together with
- Fructosamine — reflects average glucose over the previous weeks. It stays in range with short stress spikes and rises with persistent hyperglycemia, so it helps separate stress from diabetes.
- Urine glucose — glucose appears in urine once blood glucose passes the kidney threshold: about 180–200 mg/dL in dogs and 280–290 mg/dL in cats, according to eClinPath. Consistent glucosuria would be unexpected with stress alone.
- Pancreatic lipase — chronic pancreatitis can lead to diabetes, so the two are often checked together.
Units and conversion
European labs usually report glucose in mmol/L, North American labs in mg/dL. 1 mg/dL equals 0.0555 mmol/L, so 100 mg/dL is about 5.6 mmol/L. In the app each row keeps the unit printed on the form; the chart converts to one unit so forms from different labs line up.
Reference range
The reference range is on your lab’s form. It differs between labs and analysers, and glucose depends more than most values on the circumstances of the draw: how calm the animal was, when it last ate and how quickly the sample reached the lab. A value just above the range in a nervous cat means little on its own; a trend over several samples taken in similar conditions says more than one number.
Cats and dogs
Stress hyperglycemia is the main thing to know about glucose in cats: a frightened cat can show values that look like diabetes. Merck notes that several blood and urine samples may be needed to confirm diabetes in a cat, and Cornell that a single clinic reading may not be enough. Cornell lists obesity, increasing age, physical inactivity, male sex and steroid use as the main risk factors; Merck adds that many diabetic cats can reach remission and no longer need insulin.
Dogs develop milder stress hyperglycemia, usually below 300 mg/dL, so a markedly high glucose in a dog is less easily explained by nerves. Low glucose deserves particular attention in dogs: toy and small-breed puppies, hunting dogs during hard work and dogs that have eaten xylitol are known risks. Merck notes a higher risk of diabetes in dogs that have received glucocorticoids or progestins for a long time.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.