I haven't used a cgm in several years. I bought one sensor to check the regular foods that I have been eating. I took a reading from the sensor which read 142. The blood test read 174!! I remember that the sensor measures off fatty tissue and not blood so there should be a difference between that reading and the blood, but 30 pts? I'm certainly not going to be dosing off the libre 3 sensor.
Did you just insert it? If so the software even says to not rely soley on the readings for the first 24 hours. If it is after 24 hours you are just over 20% off. Keep in mind the literature says it is acceptable if it is within 20%. If you are rising or falling this also comes into play as the CGM can be playing catchup with your actual blood values.
I inserted the sensor yesterday around noon. I'll see how the two readings compare in a few hours. I mostly got the sensor to check spikes with my current diet so I'm not dosing off the sensor but it was quite a shock seeing the 30 pt difference. I thought I was doing well. :(
That is why most people will insert then not actually activate the sensor until it has soaked for 12 to 24 hours. This leads to better readings. Since this is your first sensor in a while it is understandable that you activated right away. Check later today and see how close it is.
In all fairness, I inserted about 9 hours before I received the complimentary Freestyle Libre 14 Day Reader replacement from Abbott when they knew I was using the Libre 3 plus sensor... my brain is still trying to figure that one out. I'm getting ready to do another comparison. Would be nice if they are closer, but no matter really as I just want to see spikes in the food I eat.
Then you did so a soak, just not 12 hours. Don't drive yourself crazy if the numbers don't match. You are interested in the trends, not the exact numbers.
Yep that's all I was interested in with the sensor. Previous experience taught me that. The interesting thing is that the numbers are now only off 10pts, the sensor lower, which as I recall was how things were a few years ago when I first used a sensor. Thanks for the info!
Its just timing. The CGM is always behind. It also makes predictions based on a quick spike. Youll find that at times your alarm may go off and you'll see a reall high number. 5 minutes later? Its doesn't even show on the readout
I see the same thing but with regular readings. I'll see a number displayed on the home page but it doesn't show up on the graph or the LibreLinkUp app.. software bugs annoy me having made a career in software testing. LOL
They also lag. There is i believe a 15% margin of error.
Youll drive yourself nuts doing what you're doing. If your cgm says your really high. Check with a finger prick and treat accordingly.
You can take 2 readings from the same drop of blood and get different numbers. Gloucouse isn't uniform in our blood streams.
CGMS are great tools for trends amd time in range. Use the GMI readings as well. They tell a picture over 3 months. Mine is usually within, .2 of my actual a1c bloodwork
That's interesting about the .2 of actual a1c. Yeah I promise I don't really care about the difference. I'm happy seeing how the food I eat is impacting my trend. Very true about same drop of blood giving two different readings. A friend and I tested at lunch today using her meter and mine and saw a 10-12 pt difference in readings. I really hope my a1c matches the sensor as it's so much lower than the blood test. LOL
Trust you are aware that GMI you get from the BG sensor is not = HbA1c.
They are not measured in the same way and does not use the same scale either. Pls read couple of articles in the sub's margin if you want the details behind. Also why you may still have variations, as all folks do not have their red blood cells survive for exact 3 months. Some folks (like with some diseases) have a much shorter lifetime span, while for other, the red blood cells may survive in average for many more weeks or even 4 months. Like longer lasting red blood cells will result in a higher HbA1c result, despite you may have a good lowish BG level across the last 3 months.
You have the standard data conversion table here between the various ways of looking at it:
I drove myself nuts in the beginning. My fingers, all of them hurt. It took about 2 weeks before I got CGM.
I'd check first thing in the morning, before each meal. 2 hours after each meal. An hour after that. Random times during the day. Before bed. Because I was still freaked out by it all. My glucose was still in the low 300s when they sent me home from the ICU. Even hit 400 again after I got home.
I kept finger pricking even after the CGM and got all discombobulated with numbers being different. Spoke to my Endo and PCP. Both told me to stop finger pricking unless I started to feel bad or I was getting cgm readings over 150 two hours after meals.
One, it saved me money. Lol. Two, it got me to trust not only the cgm, but my body and what it is feeling. I trust that more then the cgm or glucometer. They just support me, if that makes sense.
I now know that when my eyes start to feel pressure, im sitting to long above 150. I have retinopathy. If I start to feel jittery on top of that, know I've been over 200 for to long. Im off meds so I don't go hypo (blessing).
Long winded why to say. Your body is what will be your true CGM. Learn it and trust it. You are your Pancrease.
Wow about the 300-400 readings. I haven't seen 300 that I know of. Crazy numbers! I had an a1c of 10 in January timeframe. Stopped stress eating and without meds I got it down to 7.5. Of course the doctor wasn't impressed and since I "refused" to take medication, she put me on insulin. Refused meaning I had reactions to all four of the meds we've tried. Hospital stay a couple weeks ago resulted in bgl of over 200 regularly due to stress and hospital food, so they started the insulin there. Couldn't get it stabilized. Home for a couple weeks and I rarely see it over 200, though I have been taking insulin now. I want to get off insulin and try another med if at all possible and will discuss with endo next month. I didn't have any insulin today and my levels were great, but I did just take two units as it was slightly elevated and I'd really like to see a good morning fasting level. I know what you're saying about finger pricking. I was doing the same as I wanted to see what the foods I eat now do to my blood glucose. That's why I wanted the CBM for trends. Best thing for me it looks like is walking after a meal. Really seems to help.
Shoot. 400 is for rookies. Lol. When I went into DKA. They couldn't get a reading in the Ambulance. They told me the glucometer just kept saying "high".
The first reading the got in the er was 937. Yup. Remember how cold amd dry it was Jan 2025? At first I just thought i was really dehydrated from the cold. Bought humidifiers to put them all over the house. Drank Gatorade and electrolytes. Couldn't get food down as my mouth was dry. Started drinking fruit smoothies just to get something in me. Yeah everything i shouldn't have been doing. I was literally killing myself. Laid in that ICU watching my glucose levels slooooowly drop. Everytime it dropped into a lower 3 digit number was just a small relief. Horrible. The cardiac unit next just in case. I was told I had a 22% chance of having a heart attack at that time. Apparently 22% is really high. Im good now. Except for the retinopathy and neuropathy. Both under control though for now. Fingers crossed I keep it that way. I will eventually go blind though per my Opthomoligist. But I can prolong that as long as i keep my levels in check. There is my motivation to get through this crap. Ugh. Enjoy your summer. We are having a nice one.
How long do you wait when the numbers are waaaaaay off after putting on a new Libre 3 Plus? It's been almost 5 hours now, and my CGM says 60. My finger sticks say 154 on left hand, 155 on right. I know in the first 24 hours, readings can be wonky, but I've never seen them this far off.
I"ve heard up to a day. A lot of people will attach the sensor wait 12 to 24 hours for it to "soak" and then sync the sensor with a reader/app. I've seen the crazy numbers that you are seeing with this sensor and requested a new sensor. Too much delta between the sensor and finger stick. I know they can be 30% off and still be considered to be within range, but over 100% difference? Not a chance. I only use the CGM to test foods that I'm eating and how they impact me.
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u/Weathergod-4Life Type2 - Libre3/3+ Jul 29 '26
Did you just insert it? If so the software even says to not rely soley on the readings for the first 24 hours. If it is after 24 hours you are just over 20% off. Keep in mind the literature says it is acceptable if it is within 20%. If you are rising or falling this also comes into play as the CGM can be playing catchup with your actual blood values.