The fructosamine test for diabetes is a blood test that measures the average blood sugar level two to three weeks before the test is performed. Although similar to the hemoglobin A1C test (HbA1c), which measures the average blood sugar over the past two to four months, it is not commonly used. The shorter time window it assesses is insufficient to determine long-term prognosis.
In addition to glucose, the fructosamine test measures glycated proteins in the blood, not glycated hemoglobin. Sugar molecules present in the blood attach to proteins. These proteins circulate in the blood for 14 to 21 days, so measuring them can give you an idea of how much sugar is in your blood during this time.
Unlike the A1C test, the fructosamine test is not used as a screening test for people without diabetes or with well-controlled diabetes.
Conversely, the fructosamine test can be used in situations where the A1C test may not be reliable. E.g:
- You have blood loss or hemolytic anemia. (The rapid turnover of red blood cells means that the hemoglobin A1C test result will be falsely low.)
- You have sickle cell anemia or another hemoglobin variant.
- You have other medical conditions that may affect the reliability of HbA1c, such as kidney failure (end-stage renal disease), liver disease, HIV infection, and recent blood transfusions.
The fructosamine test is also used when your healthcare provider simply wants more information than other tests provide. In particular, it can be used if you have recently changed your medication or insulin, as it can help you assess the effectiveness of the new therapy after a few weeks. The test can also be used during pregnancy when your body is constantly changing.
Another testing option
Some health care providers may waive the fructosamine test. A 2016 review concluded that it had insufficient evidence to support its use.
The authors note that a different test that measures glycated albumin — which can also reveal short-term blood sugar levels — shows promise for the most accurate identification of prediabetes in African-Americans and non-obese people.
Another article from 2015 noted that the glycated albumin test is considered more reliable than the fructosamine test.
How the test is done
This is a blood test done at your healthcare provider’s office using a sample drawn from a vein or fingertip and analyzed in a laboratory. It is usually covered by health insurance.
As with any blood draw, the risks are minimal and no special preparation (such as fasting) is required.
A home-based fructosamine test was discontinued in 2002 because it was inaccurate.
Interpret the results
High fructosamine levels indicate high average blood sugar levels over the past two to three weeks.
Often, trends are monitored by repeating tests, whether it is fructosamine levels or other indicators such as glycated albumin or HbA1c. If the results are still high, your blood sugar is not well controlled.
Your healthcare provider will try to determine the cause and help you adjust your medications, diet, and other factors to maintain better control.
While it’s not entirely clear what fructosamine levels indicate and how they relate to diabetes or its complications, some authorities suggest the following guidelines.
- For people without diabetes, the fructosamine range should be 175-280 millimoles per liter (mmol/L).
- For people with controlled diabetes, the fructosamine range should be 210-421 millimoles per liter (mmol/L).
- For people with uncontrolled diabetes, the fructosamine range should be 268-870 millimoles per liter (mmol/L).
At times, the reliability of the fructosamine test can be compromised. Any condition that affects serum albumin production, whether it increases or decreases turnover, may affect the reliability of the fructosamine test.
Some examples of these conditions include:
- liver disease (such as cirrhosis)
- Nephrotic syndrome
- Thyroid disease
Also, high levels of ascorbic acid (vitamin C) can affect the reliability of the test. Therefore, patients should avoid taking ascorbic acid supplements for at least 24 hours prior to sample collection.
Chinese herbal medicine Polygala may also affect the results.
A fructosamine test may be part of a larger test group ordered by your healthcare provider. Take a moment to review your results and be sure to ask questions about anything you don’t understand.
Abnormal test results can be worrying, but keep in mind that there are many simple ways to control blood sugar through diet, medication, and other lifestyle changes, such as exercise. Use your test results as motivation to learn more about your diabetes and make simple changes so you can see improvement at your next test.
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