Now, we have to be careful not to try and compare apples and oranges and elephants when looking at our blood sugar numbers

At any given moment in time a Lab Test will NOT AGREE with a Stick Test which will NOT AGREE with a (flashed) instantaneous CGM Sensor Reading

Why not?

Because they are measure blood sugar at different points in the "supply chain" 😁

An A1C test is conducted on "blood plasma" which harvested from our "larger veins" - much closer to the "input source" (our digestive system)

Lab Drawn Blood gives you a blood sugar reading at the beginning of the sugar migration to the cells

A SMBG (self-monitored blood glucose) reading AKA "Stick Test" measures the sugar level in "whole blood" contain in a Capillary - it can be higher or lower (or the same) as the level of sugar in the Blood Plasma further up the food chain

And finally the CGM Sensor uses a fiber (submersed) in Interstitial Fluid - the fluid around the cells where they "suck out the sugar", which is the end of the line for blood sugar in our system

At that point it either becomes energy or body fat or simply continues to "float around" doing damage

At any instant you might have high sugar in your cell fluid and low in your plasma or vice versa or they might be the same or close

But comparing that one shot in time is irrelevant - who cares if they are "not the same" as long as the end of 3 months they all give you the same answer

And since Diabetes is managed (clinically) by monitoring your AVERAGE, it's average and not ONE Number that is important

Over a period of 90 days the Lab Drawn A1C, the collection of Stick Tests averaged by an APP or Software and the CGM Sensor average (calculated by it's APP or Software)..

ALL AGREE on what your A1C is within such a tight error rate that it is insignificant

An A1C of 6.0% equates to an average blood glucose, over the past 90 days of: 126 or 7.0 mmols

To lower that A1C to 5.8% you would only need lower your average to 120 or 6.7 mmols

Not much difference - 6 points (average) can move your A1C by 0.2% so when Lab/Stick/Sensor can all get it within 0.1% that is more than accurate enough for "any of us"

CGM's are wicked accurate - they take 1440 "stick tests" A DAY just doing their job - they know when you were eating, eating the wrong thing, doing the right thing, when you were sleeping and awake - just like Santa

Are they expensive, sure are - new technology (relatively)

Are they "as accurate" as a Lab or Stick Test?

Sure are, just don't give you the same answer at the same second

I take 7-8 Stick tests a day. 2500 per year. My numbers agree to within 1 usa, if I use the same drop of blood for any of my 3 fingerstick meters.

My A1C always agrees with the average I calculate from my stick tests within 0.1%.

I would say stick tests are quite accurate.

So an FBS stick test can give you a "snapshot" that is relevant to your management routine

Couple that with a 2-hour Post-Prandial Glucose (after meal) test every day - and best to pick your most carb intense meal of the day, typically Supper - and average your PPG or 2 hour after meal Blood test, again over the month or 3 months and that will give you a pretty good idea of where your blood sugar is "after eating"

So with the FBS (which should be your lowest "average" numbers typically) and your PPG "average" you should be able to figure, accurately enough, what "range" you have been running in AND the average of those numbers can be used to "guesstimate" your A1C

For a number of years I used Software that I could upload my Accu-Chek Guide meter (data) and it would do all the math for me (towards the end it became an APP called MySugr)

In the years that I used that, testing my FBS and after supper everyday, it NEVER Missed Calculating my A1C by more than 0.1% - it may have said 5.5 and actual was 5.4

So even with a 10% "error rate" on the meter it still got it "so close" to the lab results that it was "more than accurate enough" to give me the information I needed to manage meals, see when there was an issue (elevated fasting number) to try and solve it (or change or introduce medication etc)

The meters are fine and if you use them at least twice a day, strategically, they will provide you with what you need

But you have to "stick yourself"

Not the end of the world when you do it twice a day but if you were a Basil and Bolus Insulin user who dynamically dosed (My Father "stuck" 5 or 6 times a day - always complained about his fingers), but somebody was looking for a "better way" and that is what has led to the current CGM Sensor offerings

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@A DiabetesTeam Member

Another super article by @A DiabetesTeam Member

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I would think that sticking is accurate because you are dipping the strips directly into the blood. Layman here.