Patient Test Information

Fructosamine

Also known as:

Glycated Serum Protein; GSP

Formal name:

Fructosamine

Related tests:

Glucose; A1c; Albumin; Total Protein; Hemoglobinopathy Evaluation

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Why Get Tested?

To help monitor your blood glucose (sugar) levels over time if you have diabetes mellitus, especially if it is not possible to monitor your diabetes using the 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 to Get Tested?

When you are diabetic and your healthcare provider wants to evaluate your average blood glucose level over the last 2-3 weeks

Sample Required?

A blood sample drawn from a vein in your arm or sometimes from a fingerstick

Test Preparation Needed?

None

How is it used?

Fructosamine testing may be used to help a person with diabetes monitor and control his or her blood glucose level. 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.)

Both fructosamine and A1c tests are used primarily as monitoring tools to help people with diabetes control their blood sugar. However, 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 both tests and states that fructosamine may be considered as a substitute in situations where A1c cannot be reliably measured. Instances where fructosamine may be a better monitoring choice than 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 diabetic women who are pregnant, good glycemic control is essential during pregnancy, and the needs of the mother frequently change during gestation; 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. In these cases, fructosamine can be used to monitor glucose control.

When is it ordered?

Although not widely used, the fructosamine test may be ordered whenever a health 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 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 means that a diabetic's average 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 a person's glucose control is not adequate. This, however, does not pinpoint the cause. A review and adjustment to the person's diet and/or medication may be required to help get the person's glucose under control. Acute 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 that a diabetic has good diabetic 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 a person's 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 gastrointestinal tract, 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 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. 

Is there anything else I should know?

Since the fructosamine levels of people with well-controlled diabetes may overlap with those of people who are not diabetic, the fructosamine test is not useful as a screening test for diabetes.

High levels of vitamin C (ascorbic acid) and hyperthyroidism can interfere with test results.

What is being tested?

Fructosamine is a compound that is formed when glucose combines with protein. This test measures the total amount of fructosamine (glycated protein) in the blood.

Glucose molecules will permanently combine with proteins in the blood in a process called glycation. Affected 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 a 2 to 3 week time period.

Keeping blood glucose levels as close as possible to normal helps those 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 insulin-treated diabetics and by occasional monitoring of the effectiveness of treatment using either a fructosamine or A1c test.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm or from a fingerstick.

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.

  1. Can I test for fructosamine at home?

    No. Although a home test was available in the past, it was discontinued in 2002 after the manufacturer was purchased by another company and amid concerns that the test strips were producing falsely high results.

  2. Do I need to fast for a fructosamine test?

    No. Since it measures glycated protein and determines the average glucose over the past 2-3 weeks, the fructosamine test is not affected by food that you have eaten during the day. It can be measured at any time during the day.

  3. Shouldn't someone with a family history of diabetes have a fructosamine test?

    Not usually. Unlike A1c, this test is not recommended for screening non-diabetic people, even if they have a strong family history.

  4. 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.