A fructosamine test is a blood test used to monitor diabetes. It measures a patient’s average glucose (blood sugar) level over the past few weeks.

Along with other glucose tests, a fructosamine test can indicate how well a patient’s diabetes has been controlled and whether the average glucose level is too high. The test can also verify other blood test results, determine the effectiveness of a diabetes management plan and predict a patient’s risk of developing complications.

The test measures glycated serum protein, glucose that has bonded with proteins in blood. High levels of glycated serum protein are proportional to high levels of blood glucose. Excess glucose (hyperglycemia) is associated with many diabetic complications, such as nerve damage (diabetic neuropathy) and eye diseases.

Once glucose attaches to serum proteins, it remains there for the life of the protein, about 14 to 21 days. As a result, the evidence of high glucose is still detectable as glycated serum protein, even after blood glucose levels have returned to normal. Whereas most other glucose tests provide a “snapshot” of the amount of glucose in a person’s blood at any one time, fructosamine tests provide more of an indirect measurement of glucose levels for the past few weeks.

The glycohemoglobin test (A1C test), covering two to three months, is used more commonly to determine the effectiveness of a diabetes management plan. However, the fructosamine test has advantages in certain circumstances needing shorter-term assessment, such as pregnancy, illness, blood loss or recent adjustment of a treatment plan.