Feline Diabetes & Fructosamine

Feline diabetes mellitus is a condition where a cat's body can't properly regulate the amount of sugar in his blood. It affects about 1 in 400 cats. Diagnosing diabetes requires running blood tests to check for the level of glucose present. Several factors can influence blood glucose including stress and illness, so a single blood glucose test can be misleading. Another test that can be useful to check for diabetes is a fructosamine level. This test can be more accurate than a blood sugar alone.

  1. What is Fructosamine?

    • High fructosamine level means high glucose level.

      Fructosamine is a complex of sugar and albumin (protein), and it forms under conditions where blood glucose is high over extended periods of time. A high concentration of fructosamine in a cat's blood means a high blood glucose level and is a strong indication of diabetes mellitus.

    Fructosamine Testing to Diagnose Diabetes

    • Systemic illness and stress can affect blood glucose levels.

      When diabetes mellitus is suspected in a cat, the veterinarian will run a urinalysis and a blood chemistry, looking at your cat's blood sugar. Urine and blood glucose values can be temporarily elevated by several factors including stress and illness. Even just going to the vet and having blood drawn can raise glucose levels. Fructosamine levels measure long-term elevated blood sugar over the last two to three weeks. Checking a fructosamine concentration in addition to urine and blood glucose tests can help to differentiate between a temporary hyperglycemia (high blood sugar) and true diabetes.

    Fructosamine Testing in Monitoring Diabetes

    • Fructosamine levels can be run either with blood glucose curves or on their own to evaluate how well the cat's diabetes is being controlled on insulin therapy. A single blood glucose test will tell you the cat's blood level at that time--which again can be influenced by stress, how recently the cat has eaten, etc. The longer term view provided by a fructosamine concentration can give your vet more information about how well the insulin therapy is working over a period of time, especially when reviewed along with a blood glucose curve and physical signs. Cats that are under good control may have a fructosamine level checked once every six months.

    Normal Values

    • A well controlled diabetic will have fructosamine levels under 400 microlmol/l.

      Fructosamine concentrations are measured in micromol/l. According to Schering Plough Animal Health, a normal non-diabetic cat would have fructosamine values in the 190-365 micromol/l range. A recently diagnosed diabetic cat would have values of 350-730. A cat that is really well controlled on insulin would show values under 400. A value over 500 means that the cat's diabetes is not being controlled on insulin.

    Disadvantages of Fructosamine Levels

    • Dehydration can affect fructosamine levels.

      If your veterinarian is concerned about short-term blood sugar elevations, fructosamine concentrations aren't useful. Hyperthyroidism can affect fructosamine levels because thyroid hormones cause a high turnover rate of proteins in a cat's blood. These cats may appear to have a low fructosamine concentration even though their serum proteins may be normal. In addition, other conditions, like dehydration, that affect protein concentrations in the blood can skew the fructosamine results.