Why Bother with a Blood Sugar Monitor at Home?
Blood sugar monitor
To know what your blood glucose level is, your doctor performs several blood tests, among them a test called glycohemoglobin or HbA1c. This test in particular can help you and your doctor evaluate how well your glucose levels are controlled over the previous several weeks. So, why do you need to bother with a blood sugar monitor to test your blood sugar at home?
What is glycohemoglobin?
Inside your red blood cells there is a protein called hemoglobin that is responsible for carrying oxygen from your lungs to all tissues in your body. Glucose that circulates in your blood can attach to, or glycate, the hemoglobin inside the red cells, forming glycohemoglobin.
Once the glucose attaches to the hemoglobin, it stays there as long as the red blood cell lives, which is generally about two to three months. Old red blood cells are constantly dying and new ones are constantly being made. You might say that, at any time, your red blood cells are a mix of the very old, the middle aged, and the quite young.
Normally, in someone who does not have diabetes, about 4 to 6 percent of the hemoglobin in their blood is coated in glucose. In the person with diabetes who has blood glucose levels higher than normal, more glucose attaches to the hemoglobin molecules; usually anywhere from less than 6 percent to more than 20 percent of their hemoglobin molecules are coated in glucose.
The glycohemoglobin or HbA1c blood test measures this percentage. And because some of the hemoglobin molecules are older and some are newer, the test results provide a backward glance at the average glucose levels over the past two to three months.
Looking at these numbers can help you and your doctor evaluate how well your current diabetes therapy is working and whether any adjustments need to be made to improve your blood glucose control.
It is recommended that a person who has diabetes have a HbA1c test at least twice a year. More frequent glycohemoglobin testing may be needed when a new medication or treatment regimen is being tried or when glucose goals simply aren’t being met.
What does an HbA1c number mean?
In general, when evaluating an HbA1c test, each percent increase in the hemoglobin A1c reflects an increase in average blood glucose of 35 mg/dl. So, if an HbA1c of 6 percent is equal to an average blood glucose level of 135 mg/dl, then 7 percent would be equal to 170 mg/dl, 8 percent would equal 205 mg/dl, and so on. The American Diabetes Association recommends that the hemoglobin A1c goal be less than 7 percent for people with diabetes.
Why bother with blood sugar monitors to test your glucose at home, then?
The blood glucose monitoring you do at home gives you specific information about your glucose level at the time of the test. It allows you to take immediate action to keep your blood glucose from going way too high or way too low. Based on the reading, you may decide that you need, let us say a snack, or more insulin. It is the overall effectiveness of these day-to-day decisions, which you make based on your daily blood testing at home that will eventually reflect in your HbA1c.
HbA1c testing is not a substitute for your own daily blood glucose monitoring. The HbA1c measures only the average glucose level over the past two to three months. It can provide you with an overall picture of how well you have been controlling your blood glucose over time, or if you need to make changes in your plan. The HbA1c can’t tell you what your blood glucose level is at any one point in time; that’s why home blood glucose testing is so important.
These two types of testing, the one you do at home and the HbA1c, also serve as cross-checks for one another. For example, let us say the blood glucose tests you have being doing at home for the last couple of months indicate your levels have been in a range that reflects excellent control of diabetes.
But your HbA1c test results shows a much poorer level of control over the same period of time. It is possible that something went wrong with the HbA1c test. But it is also possible that you are not doing the home blood tests properly or often enough or that your meter is not providing accurate results.
If your HbA1c value does not agree with the average of the values recorded by your blood glucose meter, you should ask yourself the following questions:
1. Am I testing frequently enough? Checking four times a day and occasionally one hour after meals should indicate your average value.
2. Have I been testing long enough? You need to take the average of at least 6-weeks’s worth of blood glucose readings to get a valid comparison to the HbA1c.
3. Is my meter accurate? Using a single blood sample, compare the readings from your meter against readings from your doctor’s meter.
4. Do I have a medical condition that may be affecting the accuracy of my HbA1c tests? Certain conditions such as anemia caused by loss of blood, kidney disease, pregnancy, and vitamin deficiency may cause your hemoglobin molecules to have a shorter than normal life span, resulting in artificially low HbA1c values. Rarely the HbA1c value can be artificially high as a result of abnormalities in the hemoglobin itself.
Final thoughts
If you have been testing long enough, if your meter’s readings appear to be accurate, and if conditions that affect hemoglobin have been ruled out as possible factors, ask your doctor to redo your HbA1c test. If there is still a discrepancy, you will need to work with your diabetes care team to determine and correct the problem.
To your health!
Emilia Klapp, R.D., B.S.
www.TheDiabetesClub.com
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