Fructosamine

Also Known As:
Glycated Serum Protein
GSP

This article was last modified on March 25, 2021

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At a Glance

Why Get Tested?

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 To Get Tested?

When you have diabetes and your healthcare practitioner wants to evaluate your average blood glucose level over the last 2-3 weeks

Sample Required?

A blood sample drawn from a vein or sometimes from a fingerstick

Test Preparation Needed?

None

Looking For Test Results?

Looking For Reference Ranges?

You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”

For more information, please read the article Reference Ranges and What They Mean.

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. 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.

Common Questions

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?

No. 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.

Can I test for fructosamine at home?

No. Although a home test was available in the past, it was discontinued in 2002.

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.

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

No. Unlike A1c, this test is not recommended for diabetes screening, even if they have a strong family history.

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?

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

View Sources

Sources Used in Current Review

2018 review completed by Nadia Ayala-Lopez, PhD, MLS, Postdoctoral Fellow, Yale University.

American Diabetes Association. (2018). Standards of Medical Care in Diabetes. Diabetes Care, Volume 41, Supplement 1. Available online at http://care.diabetesjournals.org/content/diacare/suppl/2017/12/08/41.Supplement_1.DC1/DC_41_S1_Combined.pdf. Accessed on 10/28/2018.

National Glycohemoglabin Standarization Program (NGSP). Harmonizing Hemoglobin A1c Testing: Factors that Interfere with HbA1c Test Results. Available online at http://www.ngsp.org/factors.asp. Accessed on 10/27/2018.

National Institute of Diabetes and Digestive and Kidney Diseases. Sickle Cell Trait & Other Hemoglobinopathies & Diabetes (For Providers). Available online at https://www.niddk.nih.gov/health-information/diagnostic-tests/sickle-cell-trait-hemoglobinopathies-diabetes. Accessed on 10/27/2018.

Rifai, Nader. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Philadelphia: Saunders, 2018.

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