To help monitor your blood glucose (sugar) levels over time if you have diabetes, especially if it is not possible to monitor your diabetes using the hemoglobin A1c test; to help determine the effectiveness of changes to your diabetic treatment plan that might include changes in diet, exercise or medications, especially if they were made recently
When you have diabetes and your healthcare practitioner wants to evaluate your average blood glucose level over the last 2-3 weeks
A blood sample drawn from a vein or sometimes from a fingerstick
Glucose molecules will permanently combine with proteins in the blood in a process called glycation. These proteins include albumin, the principal protein in the fluid portion of blood (serum), as well as other serum proteins and hemoglobin, the major protein found inside red blood cells (RBCs). The more glucose that is present in the blood, the greater the amount of glycated proteins that are formed. These combined molecules persist for as long as the protein or RBC is present in the blood and provide a record of the average amount of glucose that has been present in the blood over that time period.
Since the lifespan of RBCs is about 120 days, glycated hemoglobin (hemoglobin A1c) represents a measurement of the average blood glucose level over the past 2 to 3 months. Serum proteins are present in the blood for a shorter time, about 14 to 21 days, so glycated proteins, and the fructosamine test, reflect average glucose levels over 2 to 3 weeks.
Keeping blood glucose levels as close as possible to normal helps individuals 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 in people treated with insulin and by occasional monitoring of the effectiveness of treatment using the A1c test or the fructosamine test.
How is the test used?
Fructosamine testing may be used to help people with diabetes monitor and control their blood glucose levels in cases where the A1c test cannot be used and/or a shorter-term monitoring window is desired. The level of fructosamine in the blood is a reflection of glucose levels over the previous 2-3 weeks. (See the "What is being tested?" section for more on this.) However, what this translates to in regard to outcomes and prognosis is not as validated as with A1c.
The A1c test is much more well-known and widely accepted because there are firm data that a chronically elevated A1c level predicts an increased risk for certain diabetic complications, such as problems with the eyes (diabetic retinopathy), possibly leading to blindness, kidney disease (diabetic nephropathy), and nerve damage (diabetic neuropathy).
The American Diabetes Association (ADA) recognizes the usefulness of monitoring glucose control and suggests more frequent self-monitoring of blood glucose or changing the timing of continuous glucose monitoring in situations where A1c cannot be reliably measured. The ADA states that the prognostic significance of the results of a fructosamine test are not as clear as with A1c.
Instances where fructosamine may be considered over A1c include:
- Rapid changes in diabetes treatment – fructosamine allows the effectiveness of diet or medication adjustments to be evaluated after a few weeks rather than months.
- Diabetic pregnancy – in women with diabetes who become pregnant, good glycemic control is essential during pregnancy, and the needs of the mother frequently change during the pregnancy; fructosamine measurements may be ordered along with glucose levels to help monitor and accommodate shifting glucose, insulin, or other medication requirements.
- Shortened RBC life span – an A1c test will not be accurate when a person has a condition that affects the average lifespan of red blood cells (RBCs), such as hemolytic anemia or blood loss. When the lifespan of RBCs in circulation is shortened, the A1c result is falsely low and is an unreliable measurement of a person's average glucose over time.
- Abnormal forms of hemoglobin – the presence of some hemoglobin variants, such as hemoglobin S in sickle cell anemia, may affect certain methods for measuring A1c. Furthermore, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recommends against the use of the A1c test in patients with the hemoglobin variants HbSS, HbSC, or HbCC as these patients may suffer from conditions that affect the A1c test, such as anemia, increased RBC turn-over, and frequent blood transfusions.
When is it ordered?
Although not widely used, the fructosamine test may be ordered whenever a healthcare practitioner wants to monitor a person's average glucose levels over the past 2 to 3 weeks. It is primarily ordered when a diabetic treatment plan is being started or adjusted in order to monitor the effect of the change in diet, exercise, or medication.
Fructosamine levels also may be ordered periodically when a diabetic woman who has diabetes is pregnant or when a person has an illness that may change their glucose and insulin requirements for a period of time. The fructosamine test may be used when monitoring is required and an A1c test cannot be reliably used, as in cases of a shortened RBC life span or in some cases where the person being tested has an abnormal hemoglobin.
What does the test result mean?
A high fructosamine level means that the average blood glucose over the previous 2 to 3 weeks has been elevated. In general, the higher the fructosamine level, the higher the average blood glucose level. Monitoring the trend of values may be more important than a single high value. A trend from a normal to a high fructosamine level may indicate that glucose control is not adequate. This, however, does not pinpoint the cause. A review and adjustment to diet and/or medication may be required to help get glucose under control. Illness and significant stress can also temporarily raise blood glucose levels so these factors may also be taken into account when interpreting results.
A normal fructosamine level may indicate good glucose control and that the current treatment plan is effective for the individual. Likewise, a trend from high to normal fructosamine levels may indicate that changes to the treatment regimen have been effective.
Fructosamine results must be evaluated in the context of a person's overall 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 in the urine or digestive tract, or with changes in the type of protein produced by the body. In this case, there may be a discrepancy between the results obtained from daily glucose monitoring and fructosamine testing. Also, someone whose glucose levels swing erratically from high to low may have normal or near normal fructosamine and A1c levels but still have a condition that requires frequent monitoring. However, most people with such unstable diabetic control do have elevated fructosamine and A1c concentrations.
Can a fructosamine test be used to screen for diabetes?
Can I test for fructosamine at home?
Do I need to fast for a fructosamine test?
Shouldn't someone with a family history of diabetes have a fructosamine test?
If I have diabetes, should I have a fructosamine test?
The vast majority of people with diabetes can be monitored using A1c tests that reflect their glycemic control over the previous 2 to 3 months. Fructosamine testing can be useful during pregnancy when the woman has diabetes, when a person's red blood cells have a shortened lifespan, and in some cases of people with abnormal forms of hemoglobin. Most diabetics will never need to have the test performed.
Is there anything else I should know?