What Is a Fructosamine Blood Test for Diabetes?

The fructosamine test for diabetes is a blood test that measures average blood glucose levels over the two or three weeks prior to when the test is performed. While similar to the hemoglobin A1C test (HbA1c), which measures average blood sugar over the previous two to four months, it is not as commonly used. The shorter window of time it evaluates is not sufficient for determining a long-term prognosis.

In addition to glucose, the fructosamine test measures glycated protein in the blood, instead of glycated hemoglobin. Sugar molecules present in blood adhere to proteins. These proteins circulate in the bloodstream for 14 to 21 days, so measuring them provides a picture of the amount of sugar in your blood for that time period.

Purpose of the Test

Unlike the A1C test, the fructosamine test is not used as a screening test for people who do not have diabetes or who have well-controlled diabetes.

Instead, the fructosamine test may be used in situations in which the A1C test may not be reliable. For example:

• You have had blood loss or hemolytic anemia (The rapid turnover of your red blood cells means a hemoglobin A1C test result will be falsely low.)
• You have sickle cell anemia or other hemoglobin variants
• You have another condition that may affect HbA1c reliability, such as kidney failure (end-stage renal disease), liver disease, HIV infection, and having undergone recent blood transfusions

The fructosamine test is also used when your doctor simply wants more information than another test can provide. In particular, it may be used if you've had a recent change in your medicines or insulin, as it can help gauge the effectiveness of the new treatments after just a few weeks. The test may also be used during pregnancy when your body is changing constantly.

Another Test Option

Some doctors may be moving away from the fructosamine test. A 2016 review concluded that it doesn’t have enough evidence to support its use.

The authors note that a different test that measures glycated albumin—which also reveals blood sugar levels over the short term—shows promise in most accurately identifying prediabetes in African-Americans and those who are not obese.

Another 2015 article noted that glycated albumin testing is considered more reliable than fructosamine testing.

How the Test Is Done

This is a blood test done with a sample drawn from a vein or fingerstick at your doctor’s office and analyzed in a laboratory. It is usually covered by health insurance.

Risks are minimal, as with any blood draw, and no special preparation (e.g., fasting) is required.

Interpreting Results

High fructosamine levels indicate high average blood glucose levels took place in the previous two to three weeks.

Usually, a trend is monitored with repeat testing, whether that is of fructosamine levels or other indicators, such as glycated albumin or HbA1c. If the results remain high, it shows you have not had good blood glucose control.

Your doctor will try to determine the cause and help you adjust your medications, diet, and other factors to maintain better control.

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While it's not entirely clear what fructosamine levels indicate and how they correlate to diabetes or its complications, the following guide is suggested by some authorities.

• For people without diabetes, the fructosamine range should be 175-280 mmol/L.
• For people with controlled diabetes, the fructosamine range should be 210-421 mmol/L.
• For people with uncontrolled diabetes, the fructosamine range should be 268-870 mmol/L.

Other Considerations

Sometimes, the reliability of the fructosamine test can be compromised. Any condition that affects serum albumin production, either increasing or decreasing turnover, may affect the reliability of the fructosamine test.

Some examples of these conditions include:

• Liver diseases (e.g., cirrhosis)
• Nephrotic syndrome
• Thyroid disease
• Paraproteinemia

In addition, high levels of ascorbic acid (vitamin C) can interfere with the reliability of the test. Therefore, patients should abstain from ascorbic acid supplements for a minimum of 24 hours prior to sample collection.

The Chinese herb Polygalae Radix may also affect results.

A Word From Verywell

A fructosamine test is likely to be part of a larger group of tests your doctor orders. Take your time to review your results, and be sure to ask questions about anything you don’t understand.

Getting abnormal test results can be worrisome, but remember there are many easy ways you can take control of your blood sugar with diet, medication, and other lifestyle changes, such as exercise. Use your test results as a motivator to learn more about diabetes and make simple changes so you can see improvement the next time you're tested.