What's your pre-soak sweet spot?

For those who don’t know: pre-soaking is the practice of inserting a new CGM sensor way ahead of time before switching over your transmitter at the end of a session. This is supposed to ameliorate the instability a lot of us see during the first hours of a new sensor, sometimes taking as much as 24 hrs to settle down and start giving accurate readings. There seems to be a lot of YDMV in terms of how long people need to do it to see a good effect, but do you need a really long time, like 24 hours, or will a couple of hours do it—some say 8 is plenty, maybe less? Worth determining because it has a bearing on how inconvenient the whole business is.

In that light I’ve been carrying on a kind of informal experiment over my last several sensor changes (I’m using a Dexcom G6) to see if I can figure out what my sweet spot is. Here’s what I’ve seen over my last four, including the one I started today:

  • Sensor 1: pre-soaked 6 hours. Result: flakiness settled down within ~8 hrs.
  • Sensor 2: pre-soaked 8 hours. Result: flakiness settled down within ~8 hrs.
  • Sensor 3: sanity check. Is presoak doing anything for me? Didn’t presoak at all. Result: flakiness for 24 hours.
  • Sensor 4: pre-soaked 12 hours. Result: came out of warm-up 2 hours ago and hasn’t been erratic at all. I’ve done 3 finger sticks and it’s been within 8 points the whole time. More important, I’m not seeing those sudden zig-zag ups and downs that are the hallmark of the phenomenon and tell you you can’t really rely on what your numbers are yet.

Two hours is probably too soon to be absolutely sure, and I’ve just bolused and am about to eat lunch, so we’ll see how it goes. But so far it’s looking like a 12hr pre-soak is my sweet spot. What’s yours?

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12 hours works great for me as well. If I am forced to start a sensor without a pre-soak then I usually get 6-12 hours of somewhat flaky data although not technically out of Dexcoms 30% just not quite up to my standards.

Thank you both for this information! I haven’t received my g6 yet (have never had a CGM before) and accuracy in the first hours has been my concern since my understanding is that Medicare won’t pay for strips if one has a g6. Good information! Thanks!

Is Medicare denying any prescription of strips? Like they won’t cover any if youre on a dexcom?

Dexcom told me a couple of days ago that G6 users will not be eligible for strips w/ Medicare coverage. I hope Medicare revisits that crazy decision by the time I am forced onto the G6. There are times when one must resort to strips.

I’m only on my 8th G6 sensor and I’ve only presoaked one of them.

My presoaked sensor was for 24 hours and it worked great no crazy stuff after I moved the transmitter to it and the 2 hour warmup.

One of them (no presoak) worked just fine after the the 2 hour warmup with no nonsense.

All of the others (no presoak) have severe false hypo in the first hours after the 2 hour warmup. Calibrating does no good (except perhaps knocking the sensor offline more quickly). Sometimes this is followed by a false high. The graph in the first 12 hours after those completely bogus things, shows some erraticness (some zigzagging up down 20% with a period of an hour or so).

In my super limited experience, it’s the sensor itself that is wacky for the first 24 hours, and the timing of when the transmitter is put on it seems to not really matter (except if the transmitter is in for the first hours you’re gonna get whacked out readings - not the transmitter’s fault, but the sensor’s.)

Maybe the 2 hour warmup idea for the G6 isn’t panning out and the previous (G5) 24 hour warmup is really more realistic.

That said, with a 24 hour presoak I like the G6 better because it’s only 2 hours without CGM readings then it’s back to good reliable numbers.

It is more of a challenge to wear the sticky tape 11 days than 10 days, I have found. So 5-6 days in on my presoak I put on an overpatch.

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I don’t pre-soak because, for me, it just seems like a PITA. I also agree it all depends on the sensor. Some are perfect out of the gate and others not so much. I do change my sensor in the evening, so I will occasionily get wonky readings overnight(the first 12 hours). In the morning I will test and, if needed, calibrate. That works for me. After day one, I rarely have a need to calibrate.

I also agree that medicare folks not getting any test strips is just nuts. Why I have greatly reduced my test strip use with the G6, there are times you definetly need to confirm G6 readings. For example, I always test in the morning before leaving for work, just to be sure all is good.