Fructosamine
Chemistry ·Also called: FRU, fructosamine serum, average blood glucose
What it is
When glucose circulates, a small proportion binds irreversibly to blood proteins. Those proteins live for a couple of weeks, so the amount of bound glucose is a running average rather than a snapshot of one moment.
Why your vet measures it
It answers two questions a single glucose cannot. Is this cat actually diabetic, or just frightened? And in a pet already on insulin, has control been good over the last fortnight, regardless of what today's reading says?
What a high result can mean
- Diabetes mellitus — sustained high glucose over weeks, not just at the appointment
- Poorly controlled diabetes in a pet already on insulin
- Hypothyroidism in dogs, which can raise it modestly
What a low result can mean
- Too much insulin, or prolonged periods of low blood sugar
- Low blood protein, which reduces the amount available to bind glucose
- Hyperthyroidism in cats, which speeds protein turnover and lowers the reading
Dogs and cats differ
This test earns its keep mainly in cats, where stress hyperglycaemia is routine and a diagnosis of diabetes should not rest on one glucose measurement. It is also the reason a hyperthyroid cat's fructosamine can look reassuring even when glucose control is not good.
Questions worth asking your vet
- Does this confirm or rule out diabetes for my cat?
- How has control been over the past few weeks compared with last time?
- Does my pet have any thyroid or protein problem that would skew this?
Related terms
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