How much of a bad stretch will ruin an A1C?

My latest A1C had me in the mid 7's.

Here's the thing though. I swear I'd been absolutely textbook perfect for nearly 2 months and the majority of the time was under 100, but had just had a 2 days stretch of lousy tests. Really erratic hard to account for blips that later I tracked down to be because of a leaking tube on my pump (where it meets the reservoir adapter). It was a tiny crack and was intermittent depending on the angle the pump was resting at.

My endo is a little difficult to converse with on specifics and ends up getting frustrated that you don't already know things, but I was a little confused and wanted to know why it would be this high because I'd been really good. (My print outs supported this too, but the inaccuracy of the CGM was blamed) I couldn't get a very specific estimate from him over how long it takes to boost the A1C result.

Can anyone help me out with this question?
If I theoretically had a BG of 100 for a month straight and had a single half day where my bg shot up to 300, would the A1C immediately read an average of 200ish immediately, or are things a little more subtle than this?

It frustrated the hell out of me.

A couple of things I have been told. If the "bad stretch" was close to the time when you had your A1C done, that stretch could have a larger impact on your A1C (compared to if it had happened a month earlier). In addition, I've been told before that if your BG is high for a substantial period of time (like several hours or an entire day), this will have a larger impact on your A1C than if it shoots up briefly and you correct for it and bring it down quickly.

I don't know how "true" either of these things are, but that is why it's important to not really focus so much on your A1C and look more at your BG data over several months to get a true picture of how "good" your control is. Because we T1s rely on things that are so beyond our control (the potency of insulin, mechanical devices that fail, etc), I don't think A1Cs are even close to being a "good" measure of how good we're doing.

shake it off and kick ■■■ on your next a1C. i had a similar situation this year. for the last couple years i've been at mid 6s and then in october I had a really bad stretch because of an illness and my A1C bumped up to 7.5. i'm not please but there isn't much i can do about it now but move on and show improvement on my next one.

Well, the A1c is "supposed" to measure an average over the last 90 days. So how much would your A1c be affected by having 2 days of blood sugars at 300 mg/dl? Well, if I assume you held to an A1c of 7% all the rest of the 90 days, then by my calculation, your A1c might go up to perhaps 7.1%, hardly a significant change.

ps. If your average BG has been 100, then you should have a really good A1c and this blip will not be noticable.

pps. As our fellow member Danny likes to remind us, we should never beat ourselves up over something this and instead we need to remember that "Tomorrow is another day."

Just used and Excel spread sheet 100 for 29 and 300 for one this gives me an average of 106.666 so not so bad. 2 days at 300 brings it up to 112.90 You should be good!

Like bsc I would think that some days will not have much influence. Do you think your number of red blood cells might be lower than normal? This number is important for the A1c too. Do you take iron supplements? If not I would recommend to take them for a while. I recommend the higher priced products with additional ricinus to prevent constipation.

First, your A1c is supposed to be a an average of the last 90 days, but the last 30 days carries more weight.

Second, since your A1c depends on hemoglobin exposure to glucose, it is also a measure of the time your blood cells are exposed to particular levels of glucose. Individual BG measurements do not, necessarily, reflect how much time was spent at a particular BG.I've had stretches of BGs in the 300s that have not had much of an affect on my A1c because I was able to correct them quickly. I've had overnight stretches in the 120s that have had a much bigger affect on my A1c, at least as confrimed by my CGM.

Finally. the line of correlation between A1C and Avg BG is not precise. YOUR particular relationship between YOUR Avg BG and a particular A1C may not be the same as the relationship shown in the chart.

When a red blood cell is created glucose present in the blood stream binds to the cell. This glucose stays constant until the cell dies. A1C is a measure of this bound glucose. Red blood cells are assumed to last 90 days hence the rational that A1C represents your average blood glucose reading for the previous 90 days. But in the real world some die sooner and are replaced. Thus the A1C is skewed toward the most recent week or even days reading. How much it's skewed would depend on the rate they are dieing. So plugging in averages in a spread sheet and computing averages while useful, doesn't really tell the whole story.

I download my meter readings to my computer and print out some charts for my Doc right before my appointments. I will filter for various time periods and compare average readings. For me the latest 14 day average always predicts my A1C exactly. Conversely if I have a good or bad stretch in the first 30 days of the 90 day period it seems to have comparatively little effect on what my A1c ultimately is.

Of course this depends on taking enough readings that you have a representative sample.

I do not have the scientific answers some have had, but I completely agree with everything you said. My last A1C I had great readings, except for about a week before my A1C was taken. I had two infusion set fail in a row and had an annoyingly high15-30 hours. My A1C was 0.4 higher than what I expected.

Don't beat yourself up about it. An A1C is NOT an exact science.

Seems kind of disputed though, huh?

Some say it shouldn't have effected it, and my CGM print outs supported this, yet it wasn't very good. It wasn't awful either, but by my usual accounting I was expecting far lower. I had an inkling the screw up would put me in the high 6's.

It's fabulous to have such a mine of knowledge to ask help from. Thank you all.

I think, like most things in life there are argued sciences and contradicting explanations, and as interested and pro-active diabetics we will also have a tendency to cling to those that make sense to our situation.
What I've taken from my experiences over the last 26 or so years of being a type 1, and actually reading such a vast array of experiences on this site, is that some things just don't make any sense, and what works for some won't always work for others.

Interesting comment on red blood cells. I am slightly anemic, but again my doctor hasn't explained a correlation with this and anything else, or how it would effect me in real terms as a type 1.

I really should look into getting a new endo. I seem to always walk out of there feeling like I've got 5 minutes left to live, no matter whats going on.

Anemia is supposed to lower A1C, so there's another variable to throw into the mix.

That's what I thought too, until I saw this:

I have no idea what microcytic anemia is though.

Thanks for this link, it was very helpful. Have just been diagnosed with anemia in addition to my diabetes and was wondering how the two interact.

Sadly, I've also recently learned that anemia (in particular abnormal hematocrit readings) may dramatically distort glucose meter readings. This recent study show that some meters have pretty bad errors, possibly making both the A1c and meter readings distorted.