Can a finger prick give a false low reading?

[cbooth5]

Just wanted to ask as only 8 months into diagnosis (type 1 diabetes) with very good control in honeymoon period.

I'm still adjusting things with insulin and exercise, went for a swim a coupe night ago and had pizza before, reduced by 1 unit but was physically tired from work already. I could tell my head felt heavy and maybe I had given myself an extra 0.5 units too much novorapid, as wasn't running super high (9.5 before exercising). Usually pizza sends my BMs crazy upwards. For the record I ate 90 mins before so gave it chance to spike well but it never did!

Towards the end of the swim I could tell I was on the low side but nothing drastic. My libre was reading 5.9 arrow down so I got out the pool. My body was telling me to get out the pool asap but i felt ok otherwise. I had 25g powerade, then 15g Choc bar and finger pricked. The first few said error 1 as fingers were still a bit wet for the first two. The third test worked but gave a 3.2 which I've never had before! Lowest has been 3.9. I panicked and drunk a full powerade, 10 mins later it read 6.2. I had no symptoms (usually get a bad crushing headache, cant think/concentrate etc.) other than a fast heart rate (but could have been from vigorous swimming). I want to know for safety if this is right as slightly worrying if its a true reading. Think my libre only got to 4.9.

 

[catinahat]

Yes it's possible to get a rogue reading with a finger prick test, could be a faulty strip or just the accuracy of the machines.
If you get a reading you don't expect, high or low it pays to double check by repeating the test.
Remember our testing methods are not as accurate as we would like. The manufacturing standards for accuracy are +/- 15% for 95% of the tests.
If you look at the table here https://www.diabetes.co.uk/blood-glucose-meters/blood-glucose-meter-accuracy.html you will see that even with the newer improved standards,
A reading of 3.5 means your actual level is somewhere between 2.67 and 4.33 .
When you take this into account your previous lowest of 3.9 and this 3.2 are both within this 15%. which means both results were in the same ball park
And remember this is for 95% of the tests, which means that 1 in 20 results could be outside of even the 15%.
Personally I think you did the right thing treating a possible hypo even if you didn't feel it, better to be safe than sorry.

 

[Omar51]

Yes it's possible to get a rogue reading with a finger prick test, could be a faulty strip or just the accuracy of the machines.
If you get a reading you don't expect, high or low it pays to double check by repeating the test.
Remember our testing methods are not as accurate as we would like. The manufacturing standards for accuracy are +/- 15% for 95% of the tests.
If you look at the table here https://www.diabetes.co.uk/blood-glucose-meters/blood-glucose-meter-accuracy.html you will see that even with the newer improved standards,
A reading of 3.5 means your actual level is somewhere between 2.67 and 4.33 .
When you take this into account your previous lowest of 3.9 and this 3.2 are both within this 15%. which means both results were in the same ball park
And remember this is for 95% of the tests, which means that 1 in 20 results could be outside of even the 15%.
Personally I think you did the right thing treating a possible hypo even if you didn't feel it, better to be safe than sorry.

I have been finger pricking for over 12 years.
Yes possible false reading but not too much off with my testing. Mostly if your hands are not totally cleaned and dried.