A fructosamine test is a blood test used to monitor diabetes. It measures a patient’s average glucose (blood sugar) level over the past few weeks.
Along with other glucose tests, a fructosamine test can indicate how well a patient’s diabetes has been controlled and whether the average glucose level is too high. The test can also verify other blood test results, determine the effectiveness of a diabetes management plan and predict a patient’s risk of developing complications.
The test measures glycated serum protein, glucose that has bonded with proteins in blood. High levels of glycated serum protein are proportional to high levels of blood glucose. Excess glucose (hyperglycemia) is associated with many diabetic complications, such as nerve damage (diabetic neuropathy) and eye diseases.
Once glucose attaches to serum proteins, it remains there for the life of the protein, about 14 to 21 days. As a result, the evidence of high glucose is still detectable as glycated serum protein, even after blood glucose levels have returned to normal. Whereas most other glucose tests provide a “snapshot” of the amount of glucose in a person’s blood at any one time, fructosamine tests provide more of an indirect measurement of glucose levels for the past few weeks.
The glycohemoglobin test (A1C test), covering two to three months, is used more commonly to determine the effectiveness of a diabetes management plan. However, the fructosamine test has advantages in certain circumstances needing shorter-term assessment, such as pregnancy, illness, blood loss or recent adjustment of a treatment plan.
About fructosamine tests
The fructosamine test measures the amount of glycated serum protein in the blood. Serum proteins, primarily albumin, combine (glycate) with glucose (blood sugar) to make glycated serum protein. The amount glycated serum protein is proportional to the amount of glucose in the blood. Serum is the fluid part of blood.
Whereas glucose monitoring is a method of measuring day-to-day glucose control, a fructosamine test can provide an overall view of how a diabetes management plan is working. The test measures a person’s average glucose control for the previous two to three weeks.
The test indicates recent glucose levels because once glucose attaches itself to serum protein, it remains there for the life of the protein, about 14 to 21 days. So even after blood glucose levels have returned to normal, the evidence of high glucose (hyperglycemia) is still detectable as glycated serum protein.
Benefits of a fructosamine test include:
- Confirming other test results. Fructosamine tests can verify self-testing results and blood test results from a physician.
- Determining the effectiveness of a diabetes management plan. If results are abnormal, a physician can make adjustments to a patient’s exercise plan, diet or medications.
- Predicting the patient’s risk of developing complications. High levels of glycated serum protein are equivalent to high levels of blood glucose. Hyperglycemia increases a person’s risk of developing complications such as diseases of the eyes, kidneys, nerves, heart and blood vessels.
- Encouraging the patient. Good test results can show patients the effectiveness of their decisions on diet, exercise and quitting smoking.
Although fructosamine tests can provide an idea of how well a patient’s diabetes management plan is working, there are disadvantages. Major drawbacks of solely using fructosamine tests include:
- Day-to-day glucose control is not measured. Patients must still rely on regular self-testing with a glucose meter to detect high and low glucose.
- Dosage of medication cannot be adjusted based on results of fructosamine tests. People who are prescribed insulin and certain antidiabetic agents need daily results to prevent low glucose (hypoglycemia) and high glucose.
- Many factors can cause inaccurate results, such as:
- Vitamin C.
- Hyperlipidemia (high amount of fats in the blood).
- Hemolysis (premature breakdown of the red blood cells).
- Changes in a patient’s protein levels.
- Body weight. Higher weight causes lower test results, and vice versa.
- Liver or kidney disease.
- Vitamin C.
- Providing an average of glucose levels can be misleading. Patients whose glucose levels swing erratically from high to low (unstable diabetes) may have a normal or near-normal fructosamine test result even though their glucose is not well controlled.
Although the information provided by a fructosamine test is useful, the test is not widely administered. The glycohemoglobin test (A1C test) is used more commonly to determine the effectiveness of a diabetes management plan. The test measures a person’s average blood glucose level over the past two to three months. Hemoglobin combines with glucose to make glycated hemoglobin. The glycohemoglobin test measures the amount of glycated hemoglobin, which is proportional to the amount of glucose in the blood.
Over the course of a year it would take about 18 fructosamine tests to provide the same information on glucose control as four glycohemoglobin tests. However, situations in which a fructosamine test may be ordered instead of a glycohemoglobin test include:
- When glycated hemoglobin cannot be measured or may not be useful. A fructosamine test may be ordered for patients with blood loss or abnormalities (e.g., hemolytic anemias).
- When changes in a patient’s diabetes management plan need to be evaluated quickly. The fructosamine test can reveal whether the adjustments are effective after a few weeks rather than months.
- When a woman is pregnant. Pregnancy can affect glucose by increasing a woman’s need for insulin. Fructosamine tests may be used as a way to frequently monitor and address changing glucose and insulin requirements.
- When an illness may alter a patient’s glucose levels. Fructosamine tests may be used as a way to frequently monitor and address changing glucose and insulin requirements.
- When there is a discrepancy between a glycohemoglobin test result and a patient’s record of self-testing results.
Before, during and after the test
There is no special preparation for a fructosamine test. The blood sample can be taken at any time, without the fasting that some glucose tests require. Because vitamin C and some medications can interfere with the test, patients may be asked to stop taking these substances at some point before the test.
The test is performed in a physician’s office for laboratory analysis. Blood is usually drawn from a vein (venipuncture) from the inside of the elbow or the back of the hand. First the puncture site is sterilized with antiseptic and an elastic band is wrapped around the patient’s upper arm. As a result, the pressure restricts blood flow through the vein and causes the veins below the band to fill with blood.
A needle is then inserted into a vein. Occasionally more than one puncture is necessary to locate a vein. Some people may feel a moderate level of pain when the needle is inserted, but most feel only a prick or stinging sensation. Once the needle is inserted into a vein, a tube is attached to collect the blood as it begins to flow out. The elastic band is then removed.
After the necessary amount of blood is collected, the needle is withdrawn and a small cotton ball or pad is applied with light pressure over the puncture site. After several minutes, the cotton will be discarded or replaced, and a small bandage will be placed on the puncture wound. The entire process takes less than 10 minutes. The sample is sent to a laboratory for analysis, and results are returned in several days.
Despite the precautions taken to avoid bruising and soreness, it does sometimes occur. Typically, this is not a cause for concern. To minimize soreness, patients may immediately apply a warm compress to the puncture site and repeat the application every three hours until the discoloration or pain subsides.
Patients may resume taking vitamins and medication according to their physician’s orders.
Understanding test results
It is important for patients to be aware that labs may use different tests for fructosamine and use different units when reporting results. Normal values may vary from lab to lab. Patients should be aware of the normal range for the lab their physician is using.
Test results should be evaluated in trends. When a patient’s amount of glycated serum protein has increased, this may mean that the average glucose (blood sugar) level has been higher over the previous two to three weeks. A trend from low levels to high amounts of glycated serum protein may indicate that the diabetes management plan has not been followed or is ineffective and requires adjustments. A physician may recommend adjustments in the exercise plan, diet or medication.
If changes are made, the patient may need to retest the glycated serum protein level again in a few weeks to monitor the effectiveness of the new treatment.
A trend from high levels to low amounts of glycated serum protein may indicate that adjustments to the patient’s diabetes management plan are effective and that glucose has been well controlled. However, low results can also indicate that a patient’s protein levels have changed. Falsely low results may be caused by a decrease in protein levels, an increase in protein loss or a change in the type of protein being produced by the body. Discrepancies between fructosamine test results and a patient’s record of self-testing results are often explained by changes in protein levels.
Questions for your doctor
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about the fructosamine test:
- When would I receive a fructosamine test instead of another blood glucose test?
- What is my fructosamine target range?
- Are there any medicines or over-the-counter products that could interfere with my test?
- Do I need to do anything to prepare for the test?
- When will my results be ready? Who will explain them to me, and how?
- What are my test results?
- Are there any conditions that could be skewing my results?
- Do my test results show the need for any additional tests or treatments?
- How often should I have a fructosamine test?
- What other blood tests might I need to monitor my glucose control?