New bG meters are now being held to accuracy/reliability standards which none of the CGMS machines can meet, so the FDA and EU Approvals required that CGMS devices not “pretend” to be as accurate. They would not have been approved without the official usage requiring that non-euglycemic readings be confirmed before proceeding to treatment.
Many people, however, seem to be treating their CGMS devices as a reliable indicator, at least some of the time. This is strictly “off-label” usage by the lazy… including me, on those days when I’ve verified it’s readings to be “spot on”. (Which is nearly every day after the first day, until it becomes inaccurate and I replace it about two weeks later.) Even though lots of us take action directly from CGMS readings, none of us can actually RECOMMEND it for anyone else. It’s a bad habit, and at least somewhat dangerous.
For me, using Dexcom 7+, the “delay” in CGMS readings during falling bG is nearly non-existent. (5-10 minutes.) But I nearly always see a much longer delay during rising bG.
Several of your posts seem to be focusing on “the number” (it’s precision, and promptness, and so on). But in practice, nearly all of us actual users find the trends and alarms to be the key benefit: When you see the shape of the curve change, heading towards a direction you didn’t expect, you really can treat most of your “emergencies” before they have actually occurred.
The greatest benefit in using CGMS (when you’re conscious) is seeing the trend, rather than just a few numbers. Unless you’re poking at least 8x per hour, you can’t really see the shape of the glucose curve change. You can only see a couple of points and try to fit a slope, with no idea whether it’s “steepness” is accelerating or leveling off. And of course, another huge benefit when you’re sleeping, or distracted by work and daily life, is the alarms.
Regular bG meters provide neither of these things.