This is the second in a series of postings on self-testing using an inexpensive, easy-to-use glucose meter to gain a better understanding of our glucose metabolism, far more effective than a single fasting glucose measurement performed at our annual physical. The first post examined a set of glucose measurements following a typical meal eaten by my friend, whom I’ll call “Mr. White.”
The Shortcomings of Fasting Glucose as a Diagnostic Tool
Most traditional routine physicals use fasting glucose as an indicator of how healthy our glucose metabolism is. For the reasons explained in Don’t Die Early, fasting glucose is a very poor indicator, as it is typically the last lab value to show a problem when our glucose metabolism is broken. In other words, by the time our fasting glucose shows that we’re “diabetic” or “at-risk,” we’re almost always already diabetic.
One of many reasons fasting glucose is not a reliable predictor of diabetes risk is because a person’s fasting glucose can vary dramatically from day to day, for a variety of reasons, some of which include:
- specific food, or alcohol, consumed the night before
- the time of day that the fasting glucose reading is taken
- the amount, and quality, of sleep obtained the night before
- daily variations in our glucose metabolism that are not fully understood
Mr. White, who was so kind as to let me use his postprandial glucose values for my previous posting, has supplied me with 14 fasting glucose measurements to illustrate some typical fasting glucose measurements:
Note that each of these points is a fasting glucose level from a different day. Think about the implications of this for Mr. White’s annual physical, which often uses a single fasting glucose measurement to decide if he’s “diabetic” or not.
Setting aside the many other problems with using fasting glucose as an indicator, the day-to-day variability of the morning fasting glucose means that whether Mr. White is diagnosed as “normal,” “at-risk,” or “diabetic” depends entirely upon which day, and what time of the morning, he happens to show up at LabCorp.
If Mr. White had shown up at LabCorp at day 2, for example, he would be diagnosed by his physician as “normal” but had he showed up at LabCorp at day 3, his physician would have a far different opinion about Mr. White’s risk of Type 2 diabetes and would like be offering Mr. White entirely different advice about his glucose health.
Because Mr. White spent $40 on a blood glucose meter at Walgreen’s and endured the very slight inconvenience of testing his fasting glucose a number of times, he has a much more complete picture of the state of his fasting glucose metabolism. When you consider that Mr. White also has a set of postprandial glucose measurements that reveal how his typical diet is affecting his non-fasting glucose levels, it’s clear that Mr. White has a more complete picture of his glucose health than most of us.
All for $40 and a slight inconvenience.