Pass This Test!
When it comes to blood glucose levels, your best guess may not be good enough
Before reading any farther, stop and estimate your blood glucose level. Write down the figure. Now test your glucose. How did your guess and the results of the actual test compare?
If you underestimated or overestimated your blood glucose, you're not alone. A 2005 study published in the British Journal of General Practice revealed that 60 percent of its 104 participants didn't guess correctly, either:45 people underestimated and 18 overestimated.
The results of this study are helping to settle an ongoing debate over whether people with non-insulin-dependent diabetes (that's most people with Type 2 diabetes) should test their blood glucose levels. Here's what the experts at Johns Hopkins say about the importance of testing instead of guessing your glucose level based on how you're feeling.
Understand the reasons to test
Estimating glucose levels is risky, even for people with Type 2 diabetes whose levels fluctuate over a moderate range and who have no symptoms of high or low glucose levels. “Most people feel no different whether their blood glucose reading is 95 mg/dL or 195 mg/dL. But there are huge implications for being at the high and low ends of this spectrum,” says Johns Hopkins endocrinologist Todd Brown.
The risk of long-term complications increases as average blood glucose rises. Someone whose glucose averages 195 mg/dL, for example, has a much higher risk of eye, kidney and nerve disease than someone with an average glucose level of 95 mg/dL. The risk of heart attack and stroke also increases as blood glucose averages rise.
Persistently low glucose levels could mean that your diabetes medications, some of which can cause hypoglycemia, need to be adjusted. Testing can detect low blood glucose before symptoms of hypoglycemia kick in. Symptoms include dizziness, confusion or, in severe cases, loss of consciousness.
Getting an accurate measure of your blood glucose is the only way you'll be able to tell if changes in diet, exercise and medication are working, says Christine McKinney, M.S., a diabetes educator at Johns Hopkins Bayview Medical Center. “Through testing, patients can learn to spot the signs and symptoms that may accompany high and low blood glucose levels.”
The bottom line? Testing helps everyone with diabetes get involved in managing his or her disease and become attuned to how best to control it.
Tailor testing to individual needs
How frequently to test varies depending on whether you have Type 1 or Type 2 diabetes and whether you are on insulin or oral medications. The American Diabetes Association (ADA) recommends testing daily or more often if you take insulin. If you don't take insulin, you should test often enough to know whether you are meeting your target levels but the ADA does not specify a frequency. Your health care provider will tell you how often you should test.
“I may encourage more frequent testing if there are problems with low and high glucose levels, specific concerns about the effects of exercise and diet, or if there has been a recent change in medication,” says McKinney.
Generally, it's a good idea to test before and after exercise and two hours after any meal that's a departure from your routine (at a holiday party or wedding reception, for example). Your health care provider also may advise you to test more frequently if the flu or another illness is interfering with your normal meals and activities.
Learn your trends
For newly diagnosed patients, however, McKinney proposes a month-long schedule of testing to evaluate trends in blood glucose levels. (A trend is defined as three consecutive high or two consecutive low glucose readings.) For example, if you had glucose levels of 170 mg/dL, 198 mg/dL and 164 mg/dL on Monday, Tuesday and Wednesday before lunch, this would be considered a trend of high blood glucose levels. “We would then explore why this person's blood glucose is generally high before lunch,” she explains.
Here's how McKinney's schedule works:
- Week 1: Test in a fasting state (before breakfast) and two hours after the meal.
- Week 2: Test before lunch and two hours after the meal.
- Week 3: Test before dinner and two hours after.
- Week 4: Test before bed and on waking up (the fasting test).
If you are only willing or able to test once a day, follow this schedule for pre-meal tests only. “Seven numbers taken at the same time of day over a week mean a whole lot more than random glucose levels obtained at various times,” McKinney says.
Establish a long-term testing schedule
Once someone's glucose patterns are established, the testing schedule depends on whether he or she is taking insulin and how well, overall, blood glucose is controlled, says Brown. It may help to know, however, that research has shown a link between how often people test and their A1C levels. A lower A1C level is not a direct result of more frequent testing, Brown says, but knowing about a high or low glucose level is likely to motivate you to do something about it.
Tips for effective blood glucose testing
- Keep a log of your glucose levels and bring it to every appointment. Many meters let you download readings to a computer.
- If you test high or low, determine the cause. Have you been unusually active or eaten too little or too much? Watch for and report any trends to your doctor.
- To minimize pain during testing, use a fresh lancet, test on the sides of your fingertips and rotate fingers. Some meters now have lancing devices that can be used on other sites, such as the palm, forearm, thigh or calf.
- Make sure the meter and strips are working properly. Calibrate or code your meter according to its instructions. Use the control solution manufactured for your meter routinely to check that the meter and the test strips are working together as a system. Observe the expiration and discard dates on the control solution.
