Reprinted with permission from DiabetesMine. Read more news & reviews at www.healthline.com/diabetesmine
70-120mg/dL. I think every person with diabetes has had this infamous number range ingrained in their psyche. We are constantly told that anything below 70 is considered a low blood sugar and should be treated. So when I finally got my CGM after seven years of living with type 1 diabetes, I naturally plugged this golden range of numbers into my machine. And I thus commanded my new little black box to alert me anytime my blood sugar dropped below 70.
Fast-forward four years later. I’m finishing up medical school. I’ve studied the human body and gained a better understanding of my disease. And my CGM now warns me if my blood sugar drops below 100. And my diabetes control has never been better. What? Below 100? 100 is considered low?
Allow me to explain. There have been a number of factors that have lead me to make this change:
- The CGM lags significantly behind our real blood sugar.* This is because the CGM does not measure glucose in the blood. Rather it measures glucose in the interstitial tissue fluid. You’ll notice it’s not called a “continuous blood glucose monitor” but a “continuous glucose monitor”. The missing word “blood” makes all the difference.(although I’ll admit, CGM has a better ring to it than CBGM).
- Another reason the CGM value can lag behind real BG is because it only checks every five minutes. Have you ever done intense, vigorous exercise while wearing a CGM? You’ll be able to watch your BG drop. It might read 130 when you start, then 111 five minutes later, then 96 five minutes after that. Now suppose you whip out your CGM and take a look at it four and a half minutes later. It will still say 96. In reality though, a finger stick at that point in time will probably tell you that you’re already awfully close to the hypoglycemic range.
- Lows are horrendous for overall control of BG. When BG’s dip below 70, our bodies alarm us to get some sugar into the system. One way our bodies do that is by releasing hormones that cause us to have intense hunger. (This is why I try to avoid lows when I’m in public – I’ve learned the hard way that people will look at you strangely when you finish an entire box of cereal in one sitting). Throw some clouded thinking into the mix, plus frustration at yourself for your lack of control on your BG, and you’ve got yourself a recipe for disaster. Having the self-control to eat only the required 10-15g of carbs is close to impossible. This knowledge has allowed me to devise The Hypoglycemia Roller Coaster Theorem:
Low BG= Monstrous overeating= high BG = over correcting with angry boluses= roller coaster BG for 24 hours plus. The best solution I’ve found is to simply avoid lows at all costs.
- The conventional thinking is that highs are bad in the long term and lows are just bad in the short term. However, a recent growing body of evidence is pointing towards the fact that lows may have some long term effects as well. You can read about it here.
All this has led me to set my CGM alarm at 100md/dL. This allows me to get the warning well before my blood sugar is actually in the hypoglycemic range. I then have the time to closely monitor where my BG is headed and to prevent a possible low well before it’s too late.
I will throw in one disclaimer: I don’t always have my CGM alarming under 100mg/dL. For example, if I’m going to sleep and my BG is 95mg/dL and I’m pretty certain that it will remain steady, then I’ll drop my alarm down to 85-90 (otherwise my CGM will be beeping unnecessarily all night long).
As CGM technology continues to improve, and CGM’s become more accurate, my hope is that someday I won’t need to have my alarm set at a number that is well above the hypoglycemic cutoff. But until that day comes, you’ll continue to hear me beeping away with a BG of 99mg/dL.
*Note from Dr. Edelman: Some CGM systems have a longer lag time than others. Dexcom is the best at 10 minutes and Medtronic can be quite long. Also remember that CGM alerts should always be individualized.