By Maureen Haggerty
For anyone who has diabetes, monitoring blood glucose levels is crucial.
Self-monitoring of blood glucose (SMBG testing) provides a map that guides decisions and changes in treatment components to improve diabetes control," says Susan McLaughlin, American Diabetes Association president-elect, Health Care and Education. "Tracking patterns helps individuals know when they're at greatest risk of very high or very low blood glucose, which can increase the risk of falls, result in fracture, decrease mobility, diminish quality of life, and lead to depression."
What to Look for in a Test Kit
Buy a blood glucose monitor that is portable, accurate, and reliable. Test results are sometimes reported in as little as five seconds, and almost always in less than a minute.
Monitor accuracy may decrease, and memory may be lost as batteries drain. Replacing batteries sometimes erases stored data. Other factors affecting monitor accuracy are:
- The quality of the meter and test strips
- The number of red cells in the patient's blood
- Uric acid
- Vitamin C
- Incorrect coding
Altitude, temperature, and humidity can have unpredictable effects on glucose test results. The package insert describes how to store and handle the meter and test strips.
Ease of Use
Some are easier to use than others, require less blood for testing, and store more data. Error codes, automatic timers, and barcodes make calibrating the units less complicated, and large display screens allow people with limited vision to read test results. Some monitors provide audible testing instructions and announce test results. Some speak Spanish.
The monitor manual should explain its use in words and pictures that are easy to understand. It should also explain how to interpret error codes that signify a problem with the meter, test strip, or blood sample and include the manufacturer's toll-free phone number and website address.
A Variety of Results
The monitor you select should read a wide range of glucose values. Most newer models provide "plasma equivalents." The doctor will want to know whether the monitor provides these readings, which can be 10 to 15 percent higher than values for whole blood glucose.
Test Site Options
Some monitors measure glucose in blood from parts of the body other than a fingertip. Many patients find this alternate site testing less painful than fingersticks, and results are similar when blood glucose isn't changing rapidly. Values vary after a meal or during hypoglycemic episodes. That's because blood taken from a fingertip measures "real-time" glucose levels. It's the most accurate indicator of how successfully low blood sugar has stabilized after treatment.
How to Perform SMBG Testing
- Place a small amount of blood on a disposable test strip coated with chemicals that combine with glucose.
- Insert the strip into the monitor, which measures glucose by determining how much electricity can pass though the blood sample or how much light reflects from it.
- The glucose level appears as a number on the monitor. Some monitors store test results, which can be transferred to a computer and printed or sent to the doctor.
Even if the monitor has a memory, it's important to keep a written record of results. These notes, which should include information about diet, activity, and the time the tests were taken, show how and when blood glucose values change. Take the record book to every appointment with the doctor or diabetes educator.
Inserted under the skin, continuous glucose monitors measure glucose levels in fluid around cells. Sensors relay information to a beeper-sized box or to a compatible insulin pump, which stores it. "The sensors track blood sugar trends," McLaughlin notes. "One shows how rapidly and for how long after a meal blood sugar rises or falls. This indicates whether insulin, food intake, or exercise should be adjusted."
Here are some factors to consider before testing blood glucose levels:
- Prepare the puncture site
- Make sure circulation is adequate at the site
- Use several different blood glucose monitors
- Handle and store monitors properly
- Retest if results don't reflect how he or she feels
- Contact the doctor if the problem continues
- Dispose of used test strips, lancets, and other waste materials
- Change batteries when Daylight Saving Time goes into effect
The best time for SMBG testing depends on medication, mealtimes, and sugar control. Taken during the night, fasting blood sugar (FBG) can indicate a need to adjust medication or long-acting insulin. Measuring blood glucose before a meal or at bedtime can determine whether diet or medication should be modified. SMBG testing an hour or two after eating may reflect the highest blood sugar of the day. It shows how food affects glucose levels.
The doctor may recommend more frequent testing if your loved one:
- Is ill
- Starts taking one or more new medications
- Changes his or her diet, exercise routine, or activity level
- Is experiencing stress or unusual circumstances