Readings between 2 different meters are of as much as 20

First off, Hello to all (first post/newly diagnosed with t2 )
Does anyone have experience with relion premier blu meter . i have two meters (fora g20/relion premier blu) one as a backup. tried last month to use relion after not planning ahead and running out of test strips . went to walmart and bought relion meter . but decided to try against each other and found readings to be as much 21 points from each other . nurse said meters are all calibrated to differently and not to a standard.
my note to was , Ok but one reading is good and the other has deadly consequences , and outcome of readings also fortell what to eat and what not too.


Hi @erif902! Welcome to FUD.

As far as being precise, a lot of meters can be kind of dicey like that. I tried that meter you are talking about and was not impressed.

There is really no argument about which meter is the best. It’s pretty much agreed on here that this is the meter to get. The strips are not too expensive so you can use this without any prescription. Probably just as cheap as what people pay for prescription strips.

Check out this thread on FUD:


@erif902 sadly your experience isn’t unusual. Some meters will read a 20 point difference with sequential strips from the same blood drop. As @Eric mentions, we follow all the studies of accuracy closely. Your Fora g20 is not one I have heard mentioned or seen measured in the head to head studies that researchers have done. Here is one of the studies that was published from 2017. You will notice that there is variability even within brands. It seems that some strip designs and manufacturing plants produce higher quality products.


Look at those people spending thousands of dollars to come up with the same result that I got in my kitchen.


I use Accu Check Guide meter and find it provides consistent results and find it also matches my lab draw within a couple points. Very pleased with it. I have used Contour and agree with @Eric it is a great meter.

Avoid One Touch at all costs. It is a random number generator.


Thanks to everyone who responded to my question . now i have one other reading through manual. should I get the control solution it says to do it everytime you start new test strips among other things


I never use control solution. It really doesn’t show anything about accuracy, it basically just tests the meter for “completely broken” vs “detects glucose.”


Me, neither.


Can confirm, son has been a diabetic for 6 years, never used control solution (also couldn’t tell me what it is for) and is still alive, and thriving. /s


Almost 6 years for me as well, and I still have no clue what this “control solution” is. Meter handbooks talk about it, but I figure if its that important, drug companies would have ads for it all over my fb feed. :laughing:


You have to understand the tools you use.

Two meters can both be within 10% of lab value, one high, one low, and be 20% apart.
You can get a 20% difference in two consecutive readings with one (1) meter if your technique is not good.

The ideal technique is to wash your hands thoroughly with warm water, massage, shake and dry them. That helps assure that blood is circulating through the finger capillaries . Express one drop of blood to make sure that you’re not testing with interstitial fluid, mixed in and then express a drop for testing.

If the reading is far enough outside your your control range that it requires you to make a change an insulin dose or intake, the safe thing to do is to take a second reading.

If you have two identical meters and one of them is consistently different than the other by more than 10% using strips from the same vial and control solution, it’s possible that the less accurate meter has become damaged.

But if it’s consistent then it should not be a problem to “calibrate” the result.

I always do a BG test just before blood is drawn when the lab will measure the blood glucose level. I’ve replaced meters that has been accurate when they stopped closely matching the lab results.


@psfud123 While I like the idea of testing BG just before a lab test, my recent experience at surgical clinic causes me pause. Their test of my BG before a procedures was way off of both my G6 and Contour Next One. The hospital test machine (red, 3”x3’x8”, I didn’t check the make/model) was significantly high (out of range), while the G6 and Contour were within 8 pts of each other (middle range). I told the surgical center we were going with my readings, not thier’s (they agreed and decided their machine needed checking). This wasn’t a “lab” test per se, but Lord knows how long they’d been using their machine. I’ll have to look at what labs use and how often they get tested against a known sample (control fluid?).

“A man with one watch knows what time it is…a man with two watches is never sure!”


The lab value is accurate. The bedside test machine is probably the least accurate because it gets used by so many people and rarely gets calibrated or serviced.

Your finger stick test is less accurate than the lab test result because it’s measuring capillary glucose levels which don’t match venous levels. There’s always a difference.

A finger stick test meter, if you look at a large number of tests in the middle of your control range will be within 10% with a small standard deviation.

The G6 doesn’t measure blood glucose at all. It measures interstitial glucose levels and makes an estimate based upon a large number of samples in a lab. The standards for CGMs are plus or minus 20% of a laboratory value within the control range and plus or minus 20 points outside of it, all these being in mg/dl.

CGMs aren’t useful in closed-loop systems because of their absolute accuracy but because they are sensitive to changes in the right direction. If you read the directions that is included with every single one of them they tell you not to make management decisions based upon their values but to use the fingers stick meter.


You mean like this? (

"The Dexcom G6 is FDA-permitted to make diabetes treatment decisions without confirmatory fingersticks or calibration.*

*Fingersticks required for diabetes treatment decisions if symptoms or expectations do not match readings."

Or this? (Continuous Glucose Monitoring (CGM) | FreeStyle Libre Systems)

"With the FreeStyle Libre 2 system, you can check your glucose with a painless*1,2 scan instead of fingersticks.†

† Fingersticks are required if your glucose alarms and readings do not match symptoms or when you see Check Blood Glucose symbol during the first 12 hours."


I use Accu Check meters, and I have used ReliOn meter from Walmart upon recommendation from OBGYN who’s wife had gestational diabetes, and because the test strips are so cheap. But I found it to be wildly inconsistent, so it’s a back, back, back-up now. :wink:

I’ve been Type 1 for 43 years and I’ve never used the control solution.

You have to realize that even the best meter is an estimate of your actual BG. I can find a difference of 10 to 20% between sequential BG values from different fingers!! Anyone else experience this??

Anyway, even with the advanced technology that we have available, these are still estimates of actual BG. What we want is the best estimate we can get.


The detailed FDA ruling has conditions where confirmations aren’t required. Dexcom’s advertising and their website statement meets the lawyer’s test of technically true. But it has a subtly concealed Catch-22.

How can you tell if a CGM reading doesn’t match a BG value without doing a BG test? :man_shrugging:

What you quoted is part of what’s in the 356 page Dexcom G6 User Guide. It goes on to give detailed directions how to calibrate the “no calibration required” G6 CGM if/when it doesn’t match your BGM reasonably well. Again, how can you tell without doing BG tests?

That’s a far cry from “no calibration required”. That’s like saying “no speedometer required just keep pace with the other traffic”. Try doing that with your eyes closed.

Furthermore, user experience has shown that the G6 “2 hour warm-up time” is not the time required for the G6 to be within the loosest specifications for a BGM and reliable. That time has proven to be closer to 12 to 15 hours. So a comparison/calibration can’t be done for at least 12 hours after sensor insertion when your BG is steady for at least a half hour.

Some users have also noted the accuracy of the sensors deteriorating during the 10th day. How? They did BG tests.

So of the 10 day G6 sensor llfe, the first 2 hours is unusable, the first 5% is untrustworthy and the last 5% is questionable.

For someone who had +8 A1Cs and was chronically hyperglycemic before using a CGM and under 7 afterwards, those gaps in usable accuracy may be acceptable - until they have severe hypoglycemia.

For someone like me trying to maintain tight control 24 hours day even without a CGM, those lapses can’t be ignored. I’m risk-adverse when it comes to staying alive. That’s why I always have 2 BG meters of the model I’m using, both checked with control solution and validated by a recent tab test. There are times when I BG test +8x/day (usually only 4x). I keep logs that I carefully analyse. Yes it’s a PITA, but saving my ass, eyes and extremities for another decade or more is worth it to me.

BTW, I’m not picking on the Dexcom G6. Imo it is the best of the lot of US FDA approved mediocre sensors available today. I knew exactly what its deficiencies were before getting one on order. \

By understanding what it can’t do, I can use it to improve my management without incurring greater risk. I will “trust but verify” every new sensor, just as I do the test strips and BG meters I use for verification. Only then can I rely on it to provide 1960s-quality “cruise control” of a Tandem pump. But my hand will always be on the wheel and my eyes on the irregular road of diabetes for potholes and closures.


Sequential tests that aren’t from the same drop will almost always be different. Blood flow varies between fingers on one hand and the two hands. BG fingerstick meter accuracy is already as far it can go. It will be replaced by non-invasive resonance unless the strip sellers block it.

I’ve used more kinds of BG meters in 45 years than i can remember. The docs originally told me that testing urine and 1X in the morning of NPH was good enough. I didn’t agree, I switched to MDI and multiple insulin types. Everything was out of pocket. I bought my first BG meter for so much that I had to save up for it, and paid +$1/strip when those dollars were worth 3x as much as today. I determine my insulin types and doses empirically.

I use BG readings like a level to see if I’m going up or down. I know when I’m low, and how low without a BG meter. That’s partly because using human synthetic insulin hasn’t impeded my awareness. The risk of losing that is what has held me back from using “better” kinds i=of insulin and a pump. It’s only been in the past 2 year that the tech is getting close to what I’ve been dong for +30 years. I figure it will be better that what I used to be able to do within the next 3.


@TomH, when people are talking about readings from a clinic, they are referring to lab values which @psfud123 calls out well. If it isn’t being delivered by an actual lab, then their readings are no better than yours. Portable machines just aren’t handled very well in practice, whether they are in a medical facility or not. It is the actual lab values you want to compare against from a blood draw.


Control solution is a total waste of time.


I just found a PubMed paper documenting the actual performance of the G6 (this is cross posted in the recent thread about the G7, which seems to be considerably more accurate):

So, in fact, comparing the G6 using test strip standards the G6 is worse than +/-30%,+/-30mg/dL. The test strip standards are based on ranges such that 95% or better of the tests are within range - the G6 only achieves 93.6% at the +/-30 range.

The G7 information suggests that the test being used for CGMs is not one about the absolute proportion of tests that are in a particular range (as for test strips) but the average (mean) error from the real BG [MARD]. That makes sense to me because CGMs squirt out readings continuously, test strips produce single results which we rely on without, normally, re-testing to make sure.