Unwritten Rule #1: Timing Matters for Blood Glucose Tests
In outpatient clinics, it's common to encounter diabetic patients arriving hurriedly near noon, saying, "Doctor, please test my fasting blood glucose. I haven't eaten or drunk anything." Will the doctor perform this fasting blood glucose test? The answer is "no." Even if tested, it wouldn't qualify as a true fasting measurement. Why is that?
Medical testing requires a fasting period of 12–14 hours. It's important to note that "fasting" for blood draws means abstaining from food, but water is permitted. Additionally, if you have conditions like hypertension, taking blood pressure medication is acceptable.
Fasting beyond 14 hours often leads to excessive hunger, causing changes in the body's physiological and metabolic activities.Glucose serves as the body's primary energy source—much like gasoline powers a car. Without sufficient glucose, the body cannot function properly. To maintain stable blood glucose levels, we rely on three daily meals. Additionally, during prolonged fasting periods, the liver releases stored glycogen into the bloodstream to prevent hypoglycemia, causing blood sugar levels to rise. Consequently, the glucose measured during this state does not represent true fasting blood glucose.Therefore, for fasting blood glucose testing, it's best to arrive at the clinic first thing in the morning when the doctor starts work, avoiding prolonged fasting.
For postprandial 2-hour blood glucose testing, the 2-hour period is timed starting from the first bite of food. Blood is drawn exactly 2 hours later. Many patients mistakenly believe timing starts after finishing the meal. Since postprandial blood glucose gradually decreases over time, incorrect timing will yield inaccurate results.
Unwritten Rule #2: Comprehensive Blood Glucose Monitoring
Some diabetes patients visit the hospital only to get prescriptions and medication, neglecting regular blood glucose monitoring. Others monitor blood glucose but focus solely on fasting levels, believing that controlling fasting glucose means everything is fine. These approaches are clearly incorrect.
Blood sugar levels fluctuate throughout the day like waves, rising and falling. They are generally lower during fasting, before meals, and before bedtime, while peaking after meals. To understand your blood sugar status, you need to monitor it "around the clock" at different times.
Additionally, diabetes patients should measure their "average blood sugar," which reflects glycemic control over the past 2-3 months. This "average blood sugar" is also convenient to test—blood can be drawn anytime, unaffected by timing or meals. Doctors refer to this "average blood sugar" as "glycated hemoglobin." If financially feasible, diabetes patients can test it every 3 months.
Unwritten Rule #3: Preventing Blood Glucose Test Manipulation
Many patients harbor this mindset: anticipating a blood glucose test the next day, they desperately want normal results. Consequently, they become extremely cautious about eating, strictly limiting or even skipping meals. Others, knowing exercise lowers blood sugar, avoid physical activity normally but suddenly engage in intense workouts right before testing. Some patients binge eat, eager to see how high their blood sugar can climb.
These practices are akin to "cheating." If you engage in them, the test results you receive are "false" because they don't reflect your typical blood sugar control. In a sense, the blood draw is pointless and useless.
Therefore, it is recommended that diabetes patients maintain their usual eating and exercise routines before blood tests. Avoid "cheating" to ensure the results accurately reflect your true condition. This prevents your blood from being drawn in vain and allows you to obtain genuine blood sugar results, enabling timely detection of issues and adjustments.
Unspoken Rule #4: Medication Use Before Testing
This "unspoken rule" warrants separate emphasis due to its critical importance. Many diabetes patients, especially when testing postprandial glucose, deliberately discontinue their regular hypoglycemic medications or insulin. This approach is profoundly misguided.
After a diabetes diagnosis, medication or insulin is used to manage blood sugar. The purpose of subsequent blood glucose monitoring is to assess whether the chosen treatment approach is effective, and whether the medication dosage is appropriate and sufficient. Therefore, when testing blood sugar, continue taking medication as usual to understand the "true" blood glucose control status under medication. Only then can adjustments to current diabetes medication or insulin be made based on blood glucose readings.
That concludes our explanation of the four key rules for blood glucose testing. We hope this information proves helpful. Wishing you good health and smooth sailing this winter.