Serum fructosamine levels can be used to monitor glycemic control in dogs and cats with diabetes mellitus. The term "fructosamine" refers to the albumin and other plasma proteins which have been linked to a sugar (usually glucose) by the nonenzymatic chemical reaction of glycosylation. Fructosamine concentration is proportional to blood glucose concentration over the lifespan of the glycosylated protein being measured (e.g. about 2-3 weeks for human, and 1-2 weeks for feline and canine albumin). Therefore, serum fructosamine concentration provides an assessment of an individual's average blood glucose concentration over the preceding few weeks. Serum fructosamine can be measured quickly, easily, and economically for evaluating dogs and cats with diabetes. Recently completed studies show that fructosamine concentration reflects metabolic control of diabetics more objectively than sporadic blood glucose measurements. Reference fructosamine ranges in the cat and dog are from 175-400 µmol/L and 258-343 µmol/L, respectively. Measurement of serum fructosamine should be included as part of the initial diagnostic workup in the diabetic animal and should be monitored periodically during follow-up evaluations. This test is especially helpful in the cat because fructosamine is not affected by the stress hyperglycemia which commonly occurs during blood collection. Well-regulated diabetic cats and dogs usually have serum fructosamine values below 450 µmol/L, while poorly regulated diabetics usually have fructosamine concentrations above 600 µmol/L.