Learning to use cgm

Since starting on a cgm.I am almost afraid of it.When my receiver shows a double arrow rising or lowering I get worried, especially if the number is below or above my target…I have to teach myself to not pay so much attention to the number and look at patterns more.For 30 years I have been going by the number on my glucometer to determine treatment. Can anyone give me some helpful hints on how to cope with this ?

The first thing to know is that a sensor glucose (SG) reading usually lags behind a blood glucose (BG) reading when you see double arrows rising. On the other hand, BG is probably dropping faster than SG when you see double arrows down. A fingerstick will confirm.

When I see a double arrow up, I take a moment to think about what I’ve eaten and the timing of my bolus. Often I am able to turn things around with just 5 minutes of medium exercise such as marching in place or a 15-20 walk or housework session. Sometimes, though, the overall pattern suggests I have under-bolused and need extra insulin.

I don’t worry about double arrows down unless the SG approaches or drops below my target (but do keep an eye on the numbers until the rate slows). Usually I get double arrows down only during/after exercise. So I set my low alarm higher so I can check and take on extra carbs right away as needed (and rest a bit for the carbs to kick in before resuming my activity).

Hope this helps! :smiley_cat:

As @CatLady06 has said, the Dexcom number lags actual blood glucose by about 15 minutes. Arrows up or down, double or single, shouldn’t be a cue for fear but it makes sense to pay closer attention. At these times I think of a fingerstick blood glucose number as an indication where the CGM number is headed. In effect, it allows you to see 15 minutes into the CGM’s future.

Learning how to use a CGM well requires understanding of some basic insulin management techniques. You need to understand IOB (insulin on board) and insulin sensitivity factor (ISF). You also need to have an insulin duration of action setting on your pump reasonably close to your actual. You can find info about these concepts in Scheiner’s Think Like a Pancreas and Walsh’s Using Insulin or Pumping Insulin.

You should take into account your insulin on board number. You can view your IOB on your pump. That is the amount of insulin taken earlier that has yet to take effect. So, for example, if you have a down arrow with say an 80 mg/dl reading on you CGM and your IOB is say 1.0 and your fingerstick reading is 75 then you need to take action to counteract 1 unit of insulin with a quick source of carbs. If your insulin to carb ratio, I:C, is 1:10, then that tells you that you need to take 10 grams of fast-acting carbohydrates to soften your low blood glucose (BG) landing. I like to use glucose tablets because they are a measured quantity and I can resist overdoing it.

For another scenario, let’s say the CGM reads 70 mg/dl and a fingerstick reveals 85 mg/dl, then I would do nothing because your BG is already turning around and treating it with fast acting carbs buys you a ticket on the glucose roller coaster.

Let’s say your CGM indicates 140 mg/dl and you IOB is at 0.0. If you target 110 mg/dl then you’ll need enough insulin added (or better yet, some exercise, like walking). If you wanted to take insulin, I would use your insulin sensitivity factor, or ISF, (how much one unit of insulin drops your blood sugar) to calculate how much insulin makes sense. Let’s say one unit of insulin can drop your blood sugar by 40 points (mg/dl).You would calculate 140-110=30 mg/dl. Then divide 30 by your 40 ISF number, 30/40=0.75 units of insulin needed to bring your blood sugar back to 110 mg/dl.

If your CGM shows a 140 with arrow(s) up and your IOB is at 2.0, then that means your IOB with an ISF of 40 can drop you blood sugar by 80 mg/dl. 140-80=60 mg/dl, a moderate hypoglycemic number. In this case you do nothing but watch to see how it plays out. If the trend continues up, you’ll reach a point where your calculation shows more insulin or exercise is needed.

Your CGM is like the speedometer on your car but a little more complicated. Like a speedometer, it will suggest stepping on the gas, applying the brakes, or simply doing nothing and coasting.

I apologize if I’ve thrown too much at once to you or if I’m covering ground that you already understand. Good luck with your CGM. It’s a great tool and can really blossom when you hone your understanding about how to tactically adjust your metabolic “speed.”

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Just remind yourself that your BG is doing the same things it did before you got your CGM, and you seem to have survived that unscathed. Now, you just have more information to sort through before making a much more informed decision about what to do.

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Another book that I recommend reading is Gary Scheiner’s Practical CGM. I think he has some great advice in there on how to maximize CGM usage.

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i was reading, Gary Scheiner’s Practical CGM, other then that, i can’t help much, since i stop using my cgm.

Starting on CGM can be a big psychological shock to the system. Even if you test 10+ times per day, you are still only seeing a limited selection of your BG values - with CGM there is no hiding place - every excursion outside your target zone is recorded - so your control will probably seem to be a lot worse that you thought.

When I started on CGM I had to make a significant mental adjustment. I had a few sessions with a Psychologist specializing in people with chronic medical conditions and I found that really helpful. I have established some “rules” for myself.

  1. Despite having “good control” I still have T1D and my blood glucose levels can never be those of a non-D person (however hard I try). I cannot be perfect.

  2. .I am not the subject of a self-directed one-rat experiment.

  3. Don’t take it personally. When the numbers are out of whack, correct them and move on. It’s not a value judgement.

The rest of it is just experience.

Thankyou,those were very kind and thoughtful words and rules.I read It’s a Sweet Life blog and the way that person felt is the exact same way I felt I just couldn’t describe the fear.It’s anxiety.That’s it.Now I try to tell myself that it’s only a number and I can correct it and move on.I have hypo unawareness and the cgm should keep me from going too low.I find that sometimes the number can be off so I always test before I correct or take carbs for a low.

i also like this one to !. Beyond Fingersticks: The art of control with continuous glucose monitoring.

Just read the book Sugar Surfing by Dr Ponder. Lots of good examples on how to micro tune sugars. CGM gives 288 readings a day which lets me take action before (usually) I get too high or low.
Couple of keys for me: Use alarms, especially for lows when sleeping.
Predose boluses well before eating due to the delay in insulin action (like 30-60 minutes - caution: watch for lows). Don’t eat carbs when glucose is >100 or going up.Use fats/proteins to slow carb absorption.
CGM revolutionized my understanding of my DM. Can be overwhelming at first but then can free you up to be in better control.

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