Averaging Glucose Meter Readings

[AdamJames]

It would be interesting to see if your median is more often than not the first test you do, you may find that statistically you don't need to do 3 tests..........

But I would have though the mean would be more 'accurate' as you are using 3 numbers which could be up to 15-20% off the actual result so averaging by mean should reduce the discrepancy?

Haha! My head is now going to explode.

I'm really torn now. The median has it's appeal, however for...

8.1, 8.1, 9.4

...I'd have to feel *really* confident that the 9.4 was more about meter inaccuracy than glucose levels.

And getting two numbers the same means that the "mean" is pulled very strongly towards them: it would be 8.5 in this case. Much closer to 8.1 than 9.4.

I think the real conclusion is: I need a continuous glucose monitor

 

[Bluetit1802]

Testing a particular meal just once or twice and making a decision on the result, whether an average of 3 or not, is not a good plan. Just as one example, time of day matters greatly when insulin resistance is there. Our IR varies throughout the day, as do our own insulin levels in the blood stream, and whether our liver has decided to dump just as we are eating but our pancreas is still asleep also enters the play. It can also make a difference if we don't eat the foods on our plate in the same order each time we test the meal.

Over a period of time any rogue readings will work themselves out, as there will be just as many low ones as high ones. People tend to forget that it isn't just high numbers that may be rogue ones. Swings and roundabouts. There is nothing scientific or mathematical about finger pricking.

Experience tells me what narrow range I can expect at any time of day, and anything within that range is good enough for me. If it is well outside that range I will re-test and take it from there. It doesn't happen very often. Most meters will be accurate enough most of the time.

 

[ringi]

I like median as I am less likely to make an error while doing the maths in my head.

 

[AdamJames]

Testing a particular meal just once or twice and making a decision on the result, whether an average of 3 or not, is not a good plan. Just as one example, time of day matters greatly when insulin resistance is there. Our IR varies throughout the day, as do our own insulin levels in the blood stream, and whether our liver has decided to dump just as we are eating but our pancreas is still asleep also enters the play. It can also make a difference if we don't eat the foods on our plate in the same order each time we test the meal.

Over a period of time any rogue readings will work themselves out, as there will be just as many low ones as high ones. People tend to forget that it isn't just high numbers that may be rogue ones. Swings and roundabouts. There is nothing scientific or mathematical about finger pricking.

Experience tells me what narrow range I can expect at any time of day, and anything within that range is good enough for me. If it is well outside that range I will re-test and take it from there. It doesn't happen very often. Most meters will be accurate enough most of the time.

I'd go along with that. I learned early on that porridge oats was a great food for me, until it was a horrendous one. In the end it turned out that more often than not, it's horrendous. I'd never have discovered that from doing one accurate test (3 readings either side), but it eventually became apparent with many inaccurate tests (1 reading either side) over a few weeks.

One of the many flaws in my meal-testing is that I generally test new foods at breakfast (even if the meal is not traditionally designed to be a breakfast). I do this based on some research that suggests the biggest spikes from the same food is often in the morning, so I'm hoping my results are worst-case. However I don't always re-check the same foods at other times of day, and I have no idea whether I fit that pattern. There are so many things to check to be sure of things and my fingertips are already like pin-cushions. Seriously tempted to save up for a continuous monitor; not necessarily for life, but for a few months, to get a feel for how my body works. Even then I expect it will all change a year later!

 

[slip]

...I'd have to feel *really* confident that the 9.4 was more about meter inaccuracy than glucose levels.

who to say in this 9.4, 8.1, 8.1 scenario you didn't have 2 duff strips and an accurate one..........

 

[slip]

With a CGM, you will add in another variance - the delay between interstitial fluid and Blood glucose - a delay which as with everything diabetic isn't static either.

 

[LittleGreyCat]

Haha! My head is now going to explode.

I'm really torn now. The median has it's appeal, however for...

8.1, 8.1, 9.4

...I'd have to feel *really* confident that the 9.4 was more about meter inaccuracy than glucose levels.

And getting two numbers the same means that the "mean" is pulled very strongly towards them: it would be 8.5 in this case. Much closer to 8.1 than 9.4.

I think the real conclusion is: I need a continuous glucose monitor

You also have to be aware of "confirmation bias" if you decide to ignore one reading.

Would you feel the same, for example with 8.1, 8.1, 6.7? There might be a temptation to include the more favourable outlier but ditch the less favourable outlier.

I think you are right to stick to the same methodology regardless. At least it gives consistent results.

 

[AdamJames]

who to say in this 9.4, 8.1, 8.1 scenario you didn't have 2 duff strips and an accurate one..........

With a CGM, you will add in another variance - the delay between interstitial fluid and Blood glucose - a delay which as with everything diabetic isn't static either.

Haha! Oh dear. This is turning into a very painful thread for me Brings another meaning to 'diabetes complications'!

It reminds me of a "discovery" I made recently:

I put the strip in the meter, pricked my finger, let the strip suck up the blood, and the meter dropped on the floor before it finished working things out. The strip stayed in, and the meter eventually read 2.7(!). I took another reading and got a more expected result. I wondered if that pointed to a possible way to achieve remission: If the meter dropped about 3 foot and got a reading of 2.7, maybe letting it drop just 1.5 feet would get an ideal reading? Problem solved!

 

[AdamJames]

You also have to be aware of "confirmation bias" if you decide to ignore one reading.

Would you feel the same, for example with 8.1, 8.1, 6.7? There might be a temptation to include the more favourable outlier but ditch the less favourable outlier.

I think you are right to stick to the same methodology regardless. At least it gives consistent results.

Great point. Confirmation bias is the enemy of reason and should be fought at all costs!

 

[Rachox]

Testing a particular meal just once or twice and making a decision on the result, whether an average of 3 or not, is not a good plan. Just as one example, time of day matters greatly when insulin resistance is there. Our IR varies throughout the day, as do our own insulin levels in the blood stream, and whether our liver has decided to dump just as we are eating but our pancreas is still asleep also enters the play. It can also make a difference if we don't eat the foods on our plate in the same order each time we test the meal.

Over a period of time any rogue readings will work themselves out, as there will be just as many low ones as high ones. People tend to forget that it isn't just high numbers that may be rogue ones. Swings and roundabouts. There is nothing scientific or mathematical about finger pricking.

Experience tells me what narrow range I can expect at any time of day, and anything within that range is good enough for me. If it is well outside that range I will re-test and take it from there. It doesn't happen very often. Most meters will be accurate enough most of the time.

I'd go along with that. I learned early on that porridge oats was a great food for me, until it was a horrendous one. In the end it turned out that more often than not, it's horrendous. I'd never have discovered that from doing one accurate test (3 readings either side), but it eventually became apparent with many inaccurate tests (1 reading either side) over a few weeks.

One of the many flaws in my meal-testing is that I generally test new foods at breakfast (even if the meal is not traditionally designed to be a breakfast). I do this based on some research that suggests the biggest spikes from the same food is often in the morning, so I'm hoping my results are worst-case. However I don't always re-check the same foods at other times of day, and I have no idea whether I fit that pattern. There are so many things to check to be sure of things and my fingertips are already like pin-cushions. Seriously tempted to save up for a continuous monitor; not necessarily for life, but for a few months, to get a feel for how my body works. Even then I expect it will all change a year later!

I can definitely tolerate more carbs later in the day. I always keep breakfast and lunch to less than 10g and save the majority of my carbs for my evening meal. I’ve never thought to test a meal at the ‘wrong’ time!

 

[slip]

Would you feel the same, for example with 8.1, 8.1, 6.7? There might be a temptation to include the more favourable outlier but ditch the less favourable outlier.

At least *always* using the median, the potentially misleading high or low reading(s) can be ignored then, but only then. So going to back, how often do you find the first test is the median?

 

[AdamJames]

So going to back, how often do you find the first test is the median?

Oh dear, now I think I need to do this! I think this thread has put me off numbers for life! Well maybe half an hour or so.

I don't have my data with me, but from memory, I'd say it was random as one might expect.

 

[ringi]

So going to back, how often do you find the first test is the median?

Or more to the point, "how often is the first reading within 0.3 of the median"?

 

[Bluetit1802]

I can definitely tolerate more carbs later in the day. I always keep breakfast and lunch to less than 10g and save the majority of my carbs for my evening meal. I’ve never thought to test a meal at the ‘wrong’ time!

Same with me, but I have tested berries with yogurt at breakfast, lunch and evening meal. Breakfast they were a big fat no. Lunch fared better, evening meal better still. (None of them brilliant though - fruit is a nemesis for me)

 

[ringi]

What makes us think that an increased BG does the same harm regardless of the time of day?

Remember that the research shows having most of your food at breakfast time gives the best long-term health results.....

 

[AdamJames]

What makes us think that an increased BG does the same harm regardless of the time of day?

Remember that the research shows having most of your food at breakfast time gives the best long-term health results.....

I always question research data and the interpretation of it. One interesting example is one piece of research that suggested kidney damage is more due to fluctuations in bg level, rather than the absolute value. Connecting long-term damage to exactly what an individual's blood sugar levels have been over their lifetime seems like an impossible task and we just need to make educated guesses for now, until we've had a few decades where thousands of people have worn conscious glucose monitors and had all their data and medical events collected for a study.

I'm interested in this research re breakfast if you could point me in the right direction, thanks.

 

[Boo1979]

If i were going to do 3 tests to average results in an attempt to get a really accurate idea of the effect of a particular meal, Id test the same meal on 3 different occasions and average those results rather than 3 consecutive tests on one occasion

 

[AdamJames]

If i were going to do 3 tests to average results in an attempt to get a really accurate idea of the effect of a particular meal, Id test the same meal on 3 different occasions and average those results rather than 3 consecutive tests on one occasion

Agreed, that's what I do when testing a food for how it effects me.

The three-readings thing these days I pretty much only do when testing carb tolerance to see if it's changed. The carb tolerance tests are always with exactly the same food.

 

[nailchewer]

I only do this triple-before-and-after at most once a week these days, sometimes only once every two weeks. It can cost as little as £1 depending on how cheaply I've managed to bag the strips for!

I do a before food and 2 hours after for my two main meals a day. I use urine sticks to spot trends and to monitor new foods. It seems to work. Diabetic clinic today says gold standard, and have maintained this for over 3 years.

 

[4ratbags]

Its a bit counter productive by not testing your reaction to meals at the time of the day they would normally be consumed. If you test your dinner time meal at breakfast your results may be worst case scenario but you may be eliminating a meal that if tested at dinner time may actually result in good numbers.