# Does this mean my spikes don't last long?

I just want to clarify something with A1c as a representation of good control. I know spikes can skew a good A1C reading, SO:

If I have 90% of my diabetic life had A1C's of 6.2-7.5, but never had a significant problem with LOWS, then it is unlikely my A1C's are skewed by high numbers right? For example:

Say my latest A1C was 6.9 (roughly a blood sugar of 150 on average) and I am not usually seeing numbers <100, that would also mean that I am not staying at like 200 for any length of time right? If you have a good A1C but you are not having crazy lows, that must also mean you aren't high alot, because it is an average?

Standard Deviation is the number to tell how much your BG are swinging up and down. I'm math lazy and my CGM calculates this for me but some meters will also produce report calculating SD results. I used to have a One Touch Ultra Smart that would display it but I lost it when I dropped it on a bike ride. The Wikipedia article on the subject pretty much explains it. I have a book, "Insulin Pumps and Continuous Glucose Monitoring" by Dr. Francine Kaufman that suggests that you should try to aim your SD to be < half your average BG which I'm usually able to do. I haven't seen that much about using it for a goal in other books. Unfortunately, I can't seem to find my book this AM or I'd see if there were anything else interesting in the section. :-(

I would second AR's recommendation, SD is a good target to use in order to predict your A1c.

A1c is not a average BG, it's simply a measurement of how many of your red blood cells are (stuffed with sugar at any given time) Glycated hemoglobin. A none PWD will be around 5% and a uncontrolled PWD can be as high as 25%...most of us PWD's fall somewhere in between.

I hate to say this but Unfortunately A1c is kinda like a 90 report day card.

Standard Deviation is a horrible parameter to use to answer your particular question because it simply cannot and will not tell you if your A1c is being driven by highs or lows.

You have an average BG of 150.

Let's say you have an SD of 30. Some people would say,"hey, get that down to 15 because it's a smaller number and better."

Really, whether you have an SD of 30 or 15, the assumption of the Standard Deviation calculation is the same. For every number above 150, there is a number exactly that far from your average below 150, whether those numbers actually exist or not.

You don't want a program to manufacture that for you. You want to know if that is actually true or not.

The best way to determine if your A1cs are being driven by highs or lows is to look at your actual data and do a frequency count. A frequency count is exactly what it says it is.

You count how many times you are above 150 versus the number of times you are below 150. Determine for yourself what your highest number is and what your lowest number is. Those are your real data and if you cant determine those with finger sticks from a BG meter, there is n way on this earth that SD can conjure those numbers up for you.

Even then, you're only approximating, unless you want to put a stop watch on how long you spend above 150 and how long you spend below 150 because time exposure to highs and low are also important to your A1c.

I agree that mathematically it's sort of meaningless but, when my control is tightest, my SD drops into the high teens/ low 20s. When it's loser, it runs up. With my collection of gizmos, it's readily available as a single number that requires no effort on my part to figure out, because it's just there as sort of a handy tool.

I guess I'm not quite sure how to approach it clinically as mine is a bit below Dr. Kaufman's suggestion anyway. I am certain that my A1C is driven by my own efforts rather than highs or lows. It seems like the "low A1C could still have wide swings" theory seems to be used as means to dismiss lower A1Cs as being irresponsible and I'm inclined to be dismissive of that notion.

A1c is definitely driven by highs and lows. which definitely drive average BG, which defines A1c, and round and round we can go. That's not the question or the issue here.

The OP is asking, specifically, about the ratios of highs to lows and how those relate to his A1c. The reason why SD is such a horrible parameter to use to answer this question is, specifically, because it ialready assumes within that calcuation itself that his ratio of highs to lows is exactly 1, even if it isn't.

You must understand that even if your actual BG data are skewed as hell to either highs or lows, if you calculate a standard deviation for your data, the calculation itself will simply treat the numbers as if they are not skewed to either the high or low end.

Without your average reported, you can't even report your SD and have it mean anything at all.

So, let's say your average is 86. Then, what your SD says is that you can expect about 68% of all your other actual readings to lie between 106 and 66, and about 95% of your actual readings lie between 126 and 46. That's it. That's the meaning, period, even if your data don't actually do that.

You can do a frequency distribution for every single BG reading you've already taken and determine where your variation actually is based on real numbers rather than a calculation from a formula that may or may not represent what your data actually look like.

Yeah, it's extra work, but that's the exact question that the OP is asking and there is no shortcut to the answer.

I'll add that the OP used the parameter "time", as well, which is way beyond the scope of the SD, unless you are actually measuring time itself, which we obviously are not.

So there's no difference whatsoever between 25 SD and say 70, in terms of BG control? I notice my SD will go up when I have more highs. Maybe it shouldn't, since I generally follow highs with lows, but SD seems to be pretty predictable to me.

It's not the only tool I use but it seems to offer something. Maybe I don't understand it that much. Re "time", I find the pie charts and reports from the CGM are very helpful, not in that the numbers are exact but that they cluster the reports into pre-meal and post-meal categories so I can tell if a time range, say "after lunch", is running lower b/c it has a %age of lows that's more than the other regions I can identify areas that need to be fixed. A lot of times, if I fix "after lunch" it will also pull into "before dinner" and so on and sort of fix things across the board. I think that using the most data from pump and/ or meter reports is necessary and I guess I understand your mathematical points but I just figured I'd toss it out there for something to look at. It's sort of like A1C in that it's not really "moveable" without moving your BG, which is the foundation of everything. I like any data I can see very quickly as I don't log anything and have sort of a vague idea about how things are chugging along. Sometimes, looking at the charts can help I think.

In and of themselves? There's simply not enough information from an SD alone to make any kind of determination. Standard deviation isn't calculated to predict. It's calculated to describe. You have a set of data. SD describes the variation, but only given built in assumptions about the data set.

So, let's say you have an average BG of 150.

An average bg of 150 with an SD of 15 says that you can expect to find 95% of the data between 180 and 120. That's a very tight set of BGs, but you're still dealing with an average Bg of 150 which can be improved.

An average bg of 150 with an SD of 70 says you can expect to find 95% of the data between 290 and 10. That's a huge range of BGs and probably not even representative of anything that can happen in real life.

Only you know what your SD means because only you have your complete set of data to look at.

You're absolutely correct in saying that having a lot of variables to look at is the best way to go but if you don't know what the variables are telling you, it's kinda crazy to rely on them.

Hi Christoph

I'm assuming you do not have CGMS, and probably doing most of your BG testing prior to meals, to calculate insulin dose ?.

If you want to know about how high and long your post meal spikes are, the best way is to do BG testing after meals (or get a CGMS). Your A1C cannot really help with that.

Before switching to a pump, and on MDI, I used to test 3-4/day, and only tested before meals. So my A1C always seemed high compared to my average BG on my meter/logs. When I started testing after meals, I found that after breakfast and dinner, I would have the highest spikes, often >200, where after lunch was usually < 150.

If you are using a carb ratio to determine your bolus for meals, do you have a different ratio for each meal ? Some can use the same ratio, but for many it is different at different times of the day. Some people even include protein when calculating insulin bolus.

It is great that you are not having lots of lows. But with an average of 150, it's possible your BG is close to 200 for 6-8/hours per day, after each meal. If you are able to maintain 100-120 overnight, that could average out to 150 / A1C 6.9.

Do you have a target A1C and target BG before/after meals ?

Yeah, this is a much more succinct way to say what it took me 500 words to do.

Your best bet is accurate CGM data because it generates a series of BG measurements that is roughly comparable to real time spent at given BG levels. Without CGM data, it is imperative to get enough BG measurements from finger sticks to approximate what is happening in real time. At the very least, you would need to catch your maximum and minimum BG levels. We can assume that the max BG readings will come at some point after a meal and that you are catching your lows because hypo sensitivity necessitates testing when you are symptomatic. Like you suggest, those are not guaranteed, but either way, more than the minimal 5 measurements a day are what's required.

Megaminx I think you have hit the nail on the head for what my A1C results might tell me. I am really good at keeping my overnight BG 100-120, a good amount of the day around 140-150, then post meal 200ish. BUT one thing: I think when I see this 1-2 hour postprandial test of 200ish, I immediately slam my blood sugar down as best I can with medication, hopefully minimizing this time at 200. That has been my goal all along. I guess my goal A1C in an ideal world would be a LEGIT 6.0 with my blood sugars all between 85-150. Right now I hover between A1C's of 6.3 to 7.0 or thereabouts, but I don't want these A1Cs to be misleading. I do postprandial tests and get sugars around 200 like you said, but I often think I minimize the time I spend there and KEEP IT TO A QUICK SPIKE. So at worst my A1C is telling me I am high 6-8 hours a day with the rest of the day in great shape...at BEST I'd say my sugar is usually between 100-170 right now with spikes post meal that don't last more than an hour at a time, 2-3 times a day.

Maybe the answer lies somewhere in the middle. Would you consider the worst scenario to be as bad as having an A1C of 8? If what you said was true Megaminx,what should I consider my A1C instead of a 6.9? Maybe like a 7.5?

Christoph - I think you're putting to much meaning on a LEGIT A1C. Your real A1C is what the lab said it was. It is a measurement of how much hemoglobin has attached to your blood cells at that point in time. Since blood cells live ON AVERAGE of 120 days, the A1C is correlated with what your average blood sugar is during that past 2-3 months.
But it is a CORRELATION, so what you might be thinking is that the 'real' average BG was under 150. But there's no way to 'prove' that, unless you have CGMS that provides an approximate BG reading every 5 minutes.

ADA recommends A1C < 7.0 , AACE recommends < 6.5.

A1C recommendations

Based as several studies, particularly DCCT which is mentioned in the link, the lower the A1C, the lower the risk of complications. So generally everyone tries to get as low as they can, without too many lows, or other problems.

I've had T1D for 48 years, with some vision loss, so my goal is to preserve what vision I have left, and prevent kidney and other complications. During my first 20 years, BG testing was not even available, so my BGs were likely 240-400 most of the time. They didn't measure A1C back then, but I probably had A1C of 12-14 for most of the first 20 years. So my current goal is < 6.0, which I can obtain with the help of CGMS.

Only you can decide what goal A1C is right for you. You may want to discuss with your health care team.
If you can 'hover' more on the 6.3 side than the 7.0 side, you will reduce your risk for complications.

There are tons of ideas here on TuD on things that have worked for others in lowering A1C. Unfortunately there is not a magic solution for all, and through trial and error you find what works for you.
So instead of 'slamming' down your BG when you see it ~200, you can try to avoid having it get to 200 in the first place.

My endo is pretty much like "well, if all my patients were like you, I'd be doing great" and asks me if i have alot of lows (I assume he does this because if i have alot of lows, that might also mean I have alot of highs, and it could provide an average made up of half of the time poor blood sugars). I tell him I don't have low problems, so he is basicly like great, you are in good control, if you must, bring it to like 6.7.

He is also a T1 diabetic himself. I know the responsibility falls on me, but is his logic faulty here?

Also, the link you provide basicly says after 6.5 complication risk goes up, but if you are 7 or under, well, you are still really at not in poor shape compared to 6.5. Obviously the lower the better

It is common for Endos to ask about lows (or download meters and review), as they are concerned about your safety (and others, due to car accidents etc that occur when low). If you were having many lows, he would likely discuss why and what changes to make to prevent them.

And most Endos follow the ADA guidelines, and encourage goals closer to 7.
Some would consider this 'faulty', since AACE recommendation is 6.5.
Interesting that his reply was 'If you must'..

I have seen one study that shows only 30% of adults actually have A1Cs < 7.0, so of course your endo is happy with your results.

If you continue to stay 6.3-7.0, I think you're doing great, especially since you are using MDI/shots and no CGMS. But as you said, the lower the better in terms of minimized risk of complications.

Many believe that the risk of complications is more tied to time spent > 150, rather than actual A1C. So instead of focusing on A1C, maybe you just want to consider changes that would help avoid the post meal spikes. It may have minimal impact on bringing your A1C down, but may reduce risk of complications. Many people, including me, physically feel better when staying under 150-160.

What helped me was waiting 10-20 minutes after bolus, then eating the lower-carb food items first. I also reduced/eliminated fast carbs such as breads, pasta, pizza, rice, etc.

thank you for the awesome advice!

I guess this is also good news...This article says that with an A1C <7.3 means that our post-meal numbers contribute more to the a1c then do our fasting numbers.... So I guess that since my A1C's are under 7, 70% of my a1C is representing post-prandial numbers, aka they can't be horrible with a low A1C http://www.ncbi.nlm.nih.gov/pubmed/16627379

Christoph,

How many times a day do you test, and when?

Two things to realize about our A1cs is, one, that they are a reflection of our average Blood Glucose over time and that, two, the relationship between A1c and average BG is highly variable and very individual.

When you see charts that show soandso A1c is equivalent to thisandthat average BG, those charts are based on averages of many individual A1cs and BGs, but each individual data point may be very different for every person.

Your best information about your BG numbers are your fingersticks. If you can perform enough fingersticks throughout the day to get a representative profile, you will know which numbers are driving your average BG and your A1c.

So, the primary literature you are referencing is a good place to go for general information, but because type 2 individuals with A1cs under 7.0 show that 70% of their A1cs results are due to post-prandial numbers, that doesn't necessarily mean that yours are as well. If your spikes are occurring mostly after meals, which would make sense for people who are generally under good control, then yeah, possibly. That should not change your approach to your management that much because we all fight to keep post-prandial spikes to a minimum anyway.

Some people have good control post-meal, but have a terrible time with Dawn Phenomenon, or post-workout spikes, or stress related spikes. They would, presumably, have a bigger influence on their A1cs from these other causes of high BG spikes than post-meal numbers.

You have very relevant concerns about your BG numbers and some interesting questions, but the only way to really answer your questions for yourself is to do the fingersticks and find out.