On using continuous glucose monitors (CGMs)

Bret Scher, MD of Dietdoctor.com recently interviewed Casey Means, MD, a Stanford-educated physician (both BA and MD). Dietdoctor podcast # 59 https://www.youtube.com/watch?v=336fjAmY8JQ

Dr. Means was doing an ENT surgical residency at Oregon Health Sciences Center when she realized that most of the conditions she was treating surgically (chronic sinusitis, placement of ear tubes) were inflammatory in nature and might be better treated by diet.

This opinion was not well received by her surgical peers, where the prevailing ethos was “when in doubt, cut it out”, and “you eat what you kill” (meaning that your income depends upon the procedures you perform).

She pursued metabolic health, especially the use of CGM (continuous glucose monitors, eg the Freestyle Libre and the Dexcom).

She had a number of interesting things to say, including that when CGM is studied in healthy populations, they spend 90-95% of their day in a blood glucose range of 70-120 mg/dl.

Regarding fasting glucose, lower is better. While the normal range is defined as less than 100, “70-80 (or 72-85 mg/dl) is where you want to be”.

Regarding post meal spikes in glucose, she thinks a range of 70-110 is ideal, and prefers no post meal excursions of more than 15-20 mg/dl.

Regarding the accuracy of the monitors, for the Freestyle Libre, she referenced page 16 of the FDA paper on Safety and Effectiveness, which has a nice graph showing the accuracy of the Libre at various glucose levels. https://www.accessdata.fda.gov/cdrh_docs/pdf16/P160030S017B.pdf

She notes the Dexcom can be calibrated with fingerstick blood glucose measurements, unlike the Libre.

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