Diabetes Daily has in important interview with Dr Steven Edelman on hypoglycemia (particularly in type 1 diabetes) and the need for injectable glucacon to treat it. This could easily apply also to type 2 diabetes that’s treated with insulin or other drugs that can cause hypoglycemia. Folks with type 1 diabetes seem to be more prone to hypoglycemia unawareness. That is, the blood sugar is dangerously low, but not recognized or treated promptly, potentially resulting death. Dr Edelman notes that dangerous hypoglycemia has been significantly reduced by the use of continuous glucose monitoring (CGM).
Note that CGM measure glucose levels in the the fluid in between the cells of subcutaneous tissue (AKA interstitial fluid). Your familiar fingerstick glucose is measuring capillary fluid levels. Capillaries are tiny blood vessels at the end of arteries. After going through the capillaries, blood enters veins for the return trip to the lung and heart. Glucose levels in the interstitial fluid and capillaries may not be the same as in the large arteries delivering glucose to the brain. Most CGM devices will provide the user with an alert when the glucose level drops too low, so that remedial action can be taken.
An excerpt from Diabetes Daily:
What are some ways that the CGM can most effectively help avoid hypos?
Well, one of the things I do in clinic is to really check where people set their upper and lower alerts. I had a patient yesterday in clinic who has had type 1 for 60 years. Her A1C is unbelievable, but she does have hypo unawareness and her lower alert was 65. You have to convince people that the extra alerts are worth it to you.
A lot of people said they put their lower alert at 65 and they don’t realize this situation called the “lag time.” So, when your blood sugar is dropping, even if you have a diagonal arrow down compared to, even worse, one arrow down or two arrows down, looking at the Dexcom arrows, they don’t realize that the glucose in your circulation is probably much lower than it appears on the Dexcom monitor or your phone. Because the Dexcom sensor and other sensors too, they measure the glucose in the subcutaneous tissue, and there’s a lag between the subcutaneous tissue and the circulation.
When your Dexcom goes off or when your CGM goes off at 65, and if your trend arrow’s going down, you could be 45 or 40. So that’s really an important issue, especially for people that their symptoms aren’t as obvious anymore. You could be caught off guard. And I had multiple patients that has occurred with. And then unfortunately, as you know, the majority of T1Ds in this country do not wear a CGM and that’s the topic of a whole other story.
Does this lag time issue apply to a regular glucometer as well?
Yes. If your blood sugar is dropping, your meter or CGM may be perfectly accurate of the subcutaneous tissue at 65. If you checked your blood sugar with a meter, it’s still going to say 65, but your circulation that’s going to your brain might be 45. So, the lag time is key. You could have the most accurate meter or CGM in the world, it doesn’t affect the lag time.
Click for my five-year-old article on drugs that can cause diabetes.
Click for my brief article on hypoglycemia unawareness.
Click for my general article on recognition and treatment of hypoglycemia.
Steve Parker, M.D.