Fructosamine in cats and dogs
Fructosamine is blood protein, mostly albumin, with glucose attached to it. Because these proteins last a couple of weeks, the result reflects average glucose over roughly the previous one to three weeks rather than at one moment. That makes it the vet’s main helper for telling a stress spike from diabetes and for following diabetes over time.
What it shows
Glucose in the blood slowly binds to serum proteins, especially albumin, and the product is called fructosamine. The more glucose there has been in the blood over time, the more fructosamine forms. How long it lasts depends on the life of those proteins, which eClinPath gives as generally 2–3 weeks in dogs and cats.
Sources describe the window a little differently: IDEXX and eClinPath speak of 2–3 weeks, Cornell of roughly the last two weeks, VCA of the past 7–14 days. In practice this means two things. Fructosamine is not fooled by a few stressful hours at the clinic. And it does not see what happened in the last days.
Higher than reference — what it may be a sign of
- Diabetes mellitus: persistently high glucose binds to more protein, so fructosamine rises. For an animal with high glucose at the clinic, Merck notes that fructosamine is normal in stress hyperglycemia — so a high value points towards diabetes.
- Diabetes that is not well controlled: in diabetic animals vets use repeated fructosamine to judge the response to insulin (VCA); a rising trend means glucose has been higher on average.
- Long-standing stress: eClinPath notes that on rare occasions fructosamine is increased in cats and dogs with chronic, long-lasting stress hyperglycemia.
Lower than reference
A low fructosamine can be an artefact of severe hypoproteinemia (very low blood protein): with less protein there is less to bind glucose. eClinPath adds that results appear unaffected while protein stays within reference intervals. In cats with hyperthyroidism, fructosamine was significantly lower than in healthy cats — worth knowing, because an older cat can have both an overactive thyroid and diabetes. In a diabetic animal a value lower than before means glucose was lower on average; how to read that is for the vet, together with glucose curves and how the animal is doing.
Look at together with
- Glucose — the snapshot, while fructosamine is the average. Together they separate a stress spike from diabetes.
- Urine glucose — Cornell and Merck describe diabetes as persistently high glucose in both blood and urine.
- Albumin and total protein — if they are very low, a low fructosamine may be artificial.
- Thyroid tests in older cats — hyperthyroidism can push fructosamine down.
Units and conversion
Fructosamine is reported in µmol/L (мкмоль/л on Russian forms) — the unit used by IDEXX — so there is usually nothing to convert. If a form shows a different unit, ask the lab before comparing results. In the app each row keeps the unit printed on the form.
Reference range
The reference range is on your lab’s form. Methods differ between analysers, so results from different labs are not always directly comparable, and a trend is best followed in one lab. Fructosamine is one piece of the picture: VCA’s advice for diabetic dogs pairs lab tests such as fructosamine and glucose curves with what the owner sees at home — appetite, thirst, urination and energy. A single value is read against that whole picture rather than on its own.
Cats and dogs
In cats fructosamine is especially useful because stress hyperglycemia is common and can be marked: a fructosamine within range next to a high clinic glucose suggests stress rather than diabetes. Two cautions apply. Cats with hyperthyroidism can have lower fructosamine, and because the test reflects the past weeks rather than days, a very recent change in glucose may not show up yet.
Dogs have milder stress hyperglycemia, so fructosamine is less often needed to rule out stress, but it is used to follow diabetes: VCA notes it may be recommended to evaluate a dog’s response to insulin and needs no special preparation such as fasting. As in cats, severely low blood protein can make it falsely low.
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
- eClinPath (Cornell University College of Veterinary Medicine) — Fructosamine
- IDEXX — Catalyst Dx Fructosamine Test: performance and reliability
- Buishand F. Diabetes Mellitus in Dogs and Cats. Merck Veterinary Manual
- Cornell Feline Health Center — Feline Diabetes
- VCA Animal Hospitals — Diabetes in Dogs: Testing and Monitoring
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.