What no one tells you about CGMs: Compression lows

Dexcom cover to prevent compression lows above

I don’t know why, but I’m convinced Dexcom doesn’t want you to know about compression lows. I have no idea why you never hear about them. Did you even know there was such a thing? Likely not, proving my point.

Compression lows happen when pressure is applied to the CGM sensor on your body. Most often this happens during sleep when you roll over on it, especially if you wear it on your arm, as so many of us do.

Here’s a fuller explanation of what a compression low is and why it happens. This is written by a parent of a child with type 1 diabetes. These explanations are much easier to find from those of us living with diabetes, than the manufacturers of our CGMs.

Compression lows also happen during the day. If I’m wearing my CGM on my arm, I’ll notice all of a sudden I drop like 20 points for no reason. It takes me a minute or two to realize it’s not a true drop, but the CGM on my arm is pressing against the side of my armchair, or the side of the bus I may be seated on. Move myself away from the source of pressure, and voila, my blood sugar reading rises, once again reflecting reality.

Here’s my compression low the other night while I was sleeping. Can you spot it? Pretty easy.

This is why I keep my iPhone (where I see my Dexcom readings) in my living room and not my bedroom, so these fake lows don’t wake me up in the middle of the night.

Trust me, I’m not telling you to do this. I know my body well enough after living with type 1 for five decades, and I make sure that before I go to sleep I’m at a safe number, even if I have to stay up to 2 am to make sure, which I do.

The only thing I do want you to do is to know about compression lows. Because if you don’t, it’s possible you’ll treat them, and then curse your blood sugar (and yourself) when it goes unnecessarily high. And, you know, that’s just another kick in the head living with diabetes when we already have enough.

6 thoughts on “What no one tells you about CGMs: Compression lows

  1. Riva… WOW! I wear my sensor on my abdomen per Dexcom’s recommendation. But I’m a stomach sleeper. Sounds like a problem. Thinking back I’m sure I’ve had a compression low or two or three… Not sure what to do about it except to check via glucometer if I get a dramatic low in the night. Thank you so much for this insight.

    • Hey Chad, does Dexcom not alert you at all when you’re sleeping? I would think if you have a compression low it would. Right now I’m trying a new spot, wearing it on my thigh. Amazing, I hardly remember it’s there.

      • Riva… I do get alerted in the middle of the night. But I’ve been confused. Trend line would look great until a precipitous 20-point drop for no reason. Most of the time I’d automatically treat, stay awake for 20 minutes for the uptick, and go back to sleep only to be blown away by high BS in the morning. Total mystery until now! (I so appreciate your blog!) In the future, I’ll glucometerize to confirm what’s happening. Good point about alternative sites. I’m going to experiment with both thigh and upper arm. (Saw some research that said both are acceptably reliable and valid.)

      • The only reason Dexcom only talks about wearing the device on the stomach is because that’s the only site they tested it on when applying for FDA approval. Yet, almost the entire DOC (diabetes online community) wears it all over the body, predominantly the arm. Google pix and you’ll see. I’m pretty sure most anywhere you wear it will work. Hmm…maybe I should retract that last line, but I won’t 😉

  2. Pingback: What no one tells you about CGMs: Compression lows - My Teens Heath

  3. Pingback: Oh, woe, not one, not two, but three compression lows! | Diabetes Stories

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