Fructosamine
At a Glance
Why Get Tested?
To help monitor your diabetes over time, especially if it is not possible to monitor using the HbA1C test; to help determine the effectiveness of changes to your diabetic treatment plan
When to Get Tested?
When you are diabetic and your doctor wants to evaluate your average blood glucose level over the last 2-3 weeks
Sample Required?
A blood sample taken from a vein in your arm
Test Preparation Needed?
No test preparation is needed.
The Test Sample
What is being tested?
The fructosamine test is a measurement of glycated protein, mainly albumin. When glucose levels in the blood are elevated over a period of time, glucose molecules permanently combine with proteins in the blood in a process called glycation. Affected proteins include albumin, the principal protein in the blood, other serum proteins, and hemoglobin, the protein found inside red blood cells (RBCs). The more glucose that is present in the blood, the greater the amount of glycated protein and haemoglobin formed. These combined molecules persist for the life of the protein or RBC and provide a record of the average amount of glucose that has been present in the blood over that time period.
Since RBCs live for about 120 days, glycated haemoglobin (haemoglobin A1C) represents average blood glucose levels over the past 2 to 3 months. Serum proteins have a shorter lifespan, about 14 to 21 days, so glycated proteins, and the fructosamine test, reflect average glucose levels over a 2 to 3 week time period.
Keeping blood glucose levels as close as possible to normal helps patients with diabetes to avoid many of the complications and progressive damage associated with elevated glucose levels. Good diabetic control is achieved and maintained by daily (or even more frequent) self-monitoring of glucose levels and by monitoring of the effectiveness of treatment using either a HbA1C or, occasionally, a fructosamine test.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
The Test
How is it used?
Fructosamine testing has been available since the 1980s. Both fructosamine and HbA1C tests are used primarily as monitoring tools to help diabetics control their blood sugar, but the HbA1C test is much more popular and more widely accepted. Fructosamine may be useful in situations where HbA1C cannot be reliably measured. These include:
- Rapid changes in diabetes treatment – fructosamine allows the effectiveness of diet or medication adjustments to be evaluated after a couple of weeks rather than months
- Diabetic pregnancy – good control is essential during pregnancy, and the needs of the mother frequently change during gestation; fructosamine measurements may occasionally be requested along with glucose levels to help monitor and accommodate shifting glucose and insulin requirements
- RBC loss or abnormalities – an HbA1C test will not be accurate when a patient has a condition that affects the average age of red blood cells (RBCs) present, such as haemolytic anaemia or blood loss. The presence of some haemoglobin variants may affect certain methods for measuring HbA1c. In these cases, fructosamine can be used to monitor glucose control.
Since the fructosamine concentrations of well-controlled diabetics may overlap with those of non-diabetics, the fructosamine test is not useful as a screen for diabetes.
When is it requested?
Although not widely used, the fructosamine test may be of value in the above situations.
What does the test result mean?
If a patient’s fructosamine is increased, then the patient’s average glucose over the last 2 to 3 weeks has been elevated. In general, the higher the fructosamine concentration the higher the average blood glucose level. Trends may be more important that absolute values. If there is a trend from a normal to high fructosamine, it may indicate that a patient’s glucose control is not adequate – that they are getting too much sugar, too little insulin, or that their insulin treatment has become less effective.
Fructosamine results must be evaluated in the context of the patient’s total clinical findings. Falsely low fructosamine results may be seen with decreased blood total protein and/or albumin levels, with conditions associated with increased protein loss, or with changes in the type of protein produced by the body. In this case, a discrepancy between the results obtained from daily glucose monitoring and fructosamine testing may be noticed. Also, someone whose glucose concentrations swing erratically from high to low may have normal or near normal fructosamine and HbA1C levels but still have a condition that requires frequent monitoring.
Is there anything else I should know?
High levels of vitamin C (ascorbic acid), lipaemia, haemolysis, and hyperthyroidism can interfere with test results.
Common Questions
Ask a Laboratory Scientist
Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
