Intrinsic Blood Sugar Variability

Here is some evidence of the intrinsic variability of glucose levels from my daily logbook. I always eat the exact same amount of the exact same food every day, so the calories consumed and their glycemic index are constant. I live in such a routine way that I always expend the same amount of calories per day, so activity is constant. And also, over the last six days, I have taken exactly the same amount of insulin, including Lantus and Humalog, each day at breakfast. But despite holding constant every measurable and controllable influence on blood sugar levels, they still fluctuate spontaneously in a way that frustrates all efforts at control.

So here are the blood sugar results of the first half of the last six days. I should add that I have always found such spontaneous variability typical.

Morning Blood Sugar: 50 Noontime Blood Sugar: 79
Morning Blood Sugar: 54 Noontime Blood Sugar: 103
Morning Blood Sugar: 34 Noontime Blood Sugar: 83
Morning Blood Sugar: 54 Noontime Blood Sugar: 58
Morning Blood Sugar: 49 Noontime Blood Sugar: 49
Morning Blood Sugar: 49 Noontime Blood Sugar: 148

The effect of exactly the same dose of food, insulin, and activity on the morning blood sugar seems essentially random. Two morning 54s produce afternoon values of 103 and 58, while two morning 49s produce afternoon values of 49 and 148. And yet so many doctors assume that all blood sugar variations must be because the patient did something naughty so he/she should be scolded, and even one textbook on diabetes I read introduced the chapter on complications by saying, “For diabetics who choose not to control their blood sugar, complications may develop.”

For the doctors who are are unsympathetic to the vagaries of controlling blood glucose in diabetes (not all doctors, by any means!), I’ve often fantasized about a virtual diabetes simulator for them to begin to understand the myriad inputs that influence blood glucose. I’d enjoy watching them operate this simulator with the resultant blood-glucose trace publicly displayed at one of their professional meetings.

I’ve written many times before that the definition of diabetes insanity is doing the same thing over and over and expecting the same result!


I think this type of test woud have more validity were you starting from a normal blood sugar level. You started low every morning, and so it’s possible that your body responded to some of those lows by dumping glucose while not responding to others (since we know T1’s bodies don’t always respond properly to hypoglycemia).

However, I think everyone here would agree that there’s something beyond our control that makes blood sugar fluctuate. For me, it’s hormones, weather, medications, illness (including other chronic conditions I have), and many other things. Throw in a variable schedule, and at the moment I’m dealing with an unending rollercoaster of highs and lows (at times severe) despite using every tool in my toolbox.


I’ve been doing the “D” thing since 1978. The only takeway I’ve found is that each day is different. I can eat the same foods on thousands of occasions over the years, with a different result, some of the time. Too often, actually. :slight_smile:
A few days ago I ran low for about 6 hours, in the middle of the day, with just a minor amount of activity. Very unusual. There was nothing about my meals that was unusual.

Other days I can have a bowl of my usual soup at lunch and I can hit over 200 and need a “ton” of insulin to come back into range. I feel anyone who is a T1 and can guarantee that their bg is going to be normal because they are eating “the usual” meal and getting the same amount of activity (or inactivity, as the case may be) is a lucky T1.

The only consistent thing is variability. That’s why I’m stoked to now be wearing a Dexcom! :slight_smile:

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I remember one time I was sick sick sick with a stomach bug, throwing up all the time, and all the ER doc did was test my number and have it come up 160 and scold me for that. I thought that was really supremely good given how lousy I felt (and I had been as high as 400 earlier in the day).

But wow, more than half your numbers are deep into hypo territory.

I agree with everyone else here. you can do the same thing everyday and get different results each day. the disease never seems to play fair. and I must say I am always shifting my basal rates and carb ratios. Nothing seems to stay the same for me. After 47 years, you’d think I nailed but everyday is a new experiment. I think if anyone expects the same results everyday, you are setting yourself up for some failure. Nothing stays the same and everything is always changing . I think diabetes can one of the most frustrating conditions our there. Just when you think you have it figured out, things change.
Don’t beat yourself up here. And I do agree that there are a lot of lows floating around here. And hope they are your focus right now. I have always been told to fix the lows first, than try and fix the basals. Good luck and remember, diabetes is the biggest challenge out there, especially if you want perfection.

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I’ve said the same thing myself, that I “do the same thing every day” and get wildly different results. But it’s worth keeping in mind that it is never “the same thing every day.” Activity is never “constant,” as if we were mice in a controlled experiment.

For myself, at least, the effects of even minimal activity – something that most of us would never define as activity – will be visible on my CGM. Did I go to the kitchen for a second glass of water? Did I notice some fingerprints on the fridge door while I was there and give it a wipe? Did I empty the dishwasher? Did that second glass of water mean I walked to the bathroom an extra time? Did I have to wipe the bathroom mirror after my shower, which I didn’t have to do the day before? Did I retrace my steps to the living room because I forgot my book there? Did I walk to answer a knock at the door, or dash for the phone? Did I take the garbage out? Did I get up and lower the blinds because the sun was too bright? Did I tie shoelaces today rather than wear slip-ons like yesterday?

These are all little tiny minuscule things we do that vary hour by hour, day by day. They barely register as “activity” but they are an expenditure of energy nonetheless and influence BG. I think it is impossible to say that we do the exact same thing every day.

Add that to all the myriad other variables at work, noticeable or unnoticeable, and of course we don’t get the same BG result even if we eat the same thing, take the same dose, and think we expend the same amount of energy.


WOW You nailed it! Where’s my straight jacket??

Possible very true for some but for myself it’s food, exercise and insulin. And if I don’t take any insulin, don’t eat any food and just sit and read, my blood sugars are perfect as the basals are set pretty well right now. I am very sensitive to insulin but have never really noticed going to the bathroom an extra time during the afternoon making a difference in my blood sugar or drinking an extra glass of water. I try to make things as simple as possible and if I start thinking about how many glasses of water or whether I walk or skip to the door, I would go crazy. I love having my numbers make sense but have realized a long time ago, diabetes just doesn’t work that way. I would prefer to just live my life like everyone else and not sweat the small stuff. If I mess up, fix it and move on. I just file it so maybe next time I won’t do it that way but I always realize that even with that knowledge,the next time might be different. I have given up worrying and sweating everything. The disease is very fickled.

Me too! And I, too, would go crazy if I consciously considered how quickly I should move for the phone because it will affect my blood sugars. I just have to be aware that all those little not-thought-about things add up to “activity.” So when I look at my wonky numbers and think, “That’s weird. I did the exact same thing yesterday,” in fact it’s highly unlikely I did “the exact same thing” yesterday. I might have with my food and my insulin, but I probably didn’t with my activity.

This thread began with someone saying they “expend the same amount of calories per day.” But when you think about all the little variable activities that fill a day, the calories expended may actually vary quite a bit.

Well written @Sally7. I also TRY not to sweat the small things. My personality is such that my mind just doesn’t follow suit and I end up eating needles time trying to figure out why today my bg went up when yesterday it went down for same exact food, exercise, stress, and all those other contributing factors which I try to be cognizant.:frowning:

The key point here is that the ‘small stuff’ here, the varying amounts of calories expended by small variations in activity from one day to the next, and the improved or reduced utilization of glucose from minor activity increases or decreases from one day to the next, are equally small in their impact, so they can just be discounted, with the result that there is no need to ‘sweat the small stuff.’

My experience is very similar to dave44. Since using CGMS, I worry less about counting carbs and doing calculations. I respond to the trends on my dexcom to know when to pre bolus, when to start eating, when to treat or prevent low.

I also transitioned from using the exchange diet (1980s) to carb counting with pump calculations. But use of CGMS allows me to better respond to the multitude of factors that impact BG, by just watching trend, and consider other factors such as food already eaten, exercise in past or planned, illness, stress, etc. And make lots of mini corrections with food, pump bolus or Afrezza.


Exchanges blew my mind, like Analytical Geometry, which I failed in college. I gave up trying to work with exchanges 9 (late 70’s- 80’s). It wasn’t until 1996 when I was getting prepared to get my first pump. that I put carb counting into practice. Wow, what a difference!

In hindsight , it was ridiculous that they didn’t teach carb counting and carb ratios for dosing until you went on a pump. For years my logs showed I took NPH plus 5 units REG for each meal, but only tested BG before meals, and almost always added 2 correction units for high BG before the meal. No pre-bolus, so no wonder I was still high before the next (high carb) meal.

And I was considered a star patient because I didn’t have low blood sugars, or DKA. And got an atta- boy for getting A1C in the 9s.

The availability of forums, blogs, like this and many great books has enabled folks today many more advantages and improved health.

I was taught carb count and ratios long before I was on an insulin pump. I was taught carb count when I was on oral medication then ratios when started on sliding scale insulin. To this day all by glucose readings go to my Endo every 10 days for review and revisions if needed.

I’m literally laughing out loud as I’ve designed this same simulation in my head! :joy:

It’s time for one of my favorite memes. IMG_5993


There is a saying among endocrinologists, which is that “there are no brittle diabetics, but only diabetics who don’t bother controlling their blood sugars.” I am convinced now after having spent many years adhering to exactly the same amount of activity, exactly the same amount of calories consumed, exactly the same kinds of food eaten, exactly the same feeding times, and maintaining exactly the same weight for years on end, as well as meticulously recording all my blood sugar values and insulin doses, that the intrinsic variability of the blood sugar levels is so massive that it completely swamps any and all factors that can be controlled and measured, such as calories consumed, activities performed, and insulin taken.

For example, my job requires me to lecture to students, and the stress of lectures often elevates my blood sugar level by a good 80 points, but sometimes it doesn’t. I can only assume that this has to do with my emotions about the lecture and the students’ questions or reaction to it, yet there is no way to know in advance how my body is going to react to such situations or how much sugar it is going to produce or not because of them. So, since emotion has such a colossal impact on blood sugar levels and cannot be predicted, calculated, or controlled, blood sugar is also not controllable, however much you obsess over keeping all the measurable variables in line.

So never let anyone blame you for poor blood sugar control, since it is in large part controlled by your subconscious mind and its physiological effects, which are outside your control.


It wasn’t until Stephen Ponder published Sugar Surfing in 2015 did I realize that my static thinking about blood sugar control was part of the problem. I was taught about insulin to carb ratios (I:C), insulin sensitivity (ISF), and correction factors (CF). These are all static formulas with a retrospective bias. They all look backward in time to give an answer that you hope will work going forward.

We all can appreciate the many factors beyond food and exercise that influence our blood glucose (BG) levels. Instead of trying to quantify every last factor that influences your BGs, Ponder just accepts this variability. Instead he responds to what’s happening now, usually with the aid of a continuous glucose monitor. He calls this dynamic response to fresh trends, sugar surfing.

From Ponder’s Sugar Surfing website:

I find Ponder’s analysis refreshing in that I don’t have to look at every last influence of my blood glucose and attempt to quantify it and plug it into some static formula. I still find the static formulas useful, however. I hope that my “best guesses” derived from formulas for insulin dosing will at least get me into the right BG neighborhood. Then I can employ dynamic sugar surfing techniques to respond to whatever my metabolism decides to throw at me that day. I can use temporary basal rates in my pump to add or subtract from my programmed basal rates. I can also use the inhaled insulin Afrezza to quickly pull down a trend toward hyperglycemia.

I mostly depended on Ponder’s system for about a year until I switched to an automated insulin dosing system that I now use. These automated systems can do sugar surfing better since the computer can look at my status every five minutes and make a rational decision whether to increase, decrease, or stand pat with my basal insulin delivery.

If I were not using my current technology, I would definitely be using sugar surfing tactics.


I love his stateyabout thinking one can “control” their diabetes. My thinking now is, I work with it. I sure don’t contro it and it doesn’t control me. Some days we get along and some days we don’t. I agree that have some baseline numbers is always a good starting point but being flexible is a must and understanding what worked yesterday probably won’t today. I have kinda given up trying to figure it out. I just look at the number and decide what to do.
I do love the surfing ideas. Years ago it was great every low with 15 grams of carbohydrates and retest in 15 minutes. I now know that maybe one tablet will be just enough to pull me back into line or .5 unit of insulin will pull me back into line. Do I stress about not being in target? Not anymore! I just try and learn what I can from each experience and sometimes, I just don’t care to figure it out, I just move on!
And yes, one day we will all have the option to have a little computer do all the thinking for us! Can’t wait!