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We’ve all heard people who don’t have diabetes minimize the struggle of management thinking it’s all math. “Oh so your CGM tells you what your blood sugar is, so you just count carbs and put it in your pump and it does the rest for you” Even our clinicians often act as if just getting the math right holds the key to all things blood sugar control, endlessly harping on carb counting as the singular cause of all our diabetes management struggles. We do it too! Sometimes we can get obsessed with finding the “magic math” that will make it all work, testing insulin sensitivity and carb ratios over and again only to get more and more frustrated when the magically perfect ratios don’t present themselves.

If diabetes management were all in the math it’d be easy!

And this is coming from someone who HATES math! I stayed after school and had a tutor in the third grade because I was SO BAD at math! ( a huge thanks to Mrs Adkins, Mrs Stewart and my mom for pushing me through that, because diabetes management and my entire nursing career is rooted in 3rd grade math!)  But as people with diabetes we can’t become fixated on the math.


Here are some eye opening realities about the numbers we can become focused on:

Blood sugar values: even the most accurate Meters are FDA approved to be 15% off for 85% of their readings. (the remaining readings can be even further off!)  The most accurate meter, the Contour Next, is ranked as roughly 99% lab accurate, but that still leaves room for enough error to skew the math when we are testing things like insulin sensitivity. When we then mix in the further accuracy issues, and delayed response of CGM, we can see where looking for precision in the numbers can become an endless exercise in frustration.

Carb counts: Did you know that even individually packaged foods are approved to be up to 20% off in their nutritional labeling for carb counts! So even if we are weighing our foods and have a label (the highest possible carb counting accuracy) we can still be off by 20% and have no way of knowing it! So in theory if we have a 1:20 carb count, and take 1 unit and eat 20 grams of food with the perfect insulin timing blood sugars should be spot on, and replicable. But the reality is that you really can eat that waffle one day and see a different result the next day, because the waffle itself might have thrown your carb count off. Combine that with your meter running 10% high one day and 10% low the next… And so the pursuit of that perfect carb ratio by testing it repeatedly is

Insulin Dosing:  Even in the most critical parts of our blood sugar management the numbers we base our decisions on are not as precise as we think of them to be. Insulin pens are approved with variability of ISO recommendations (1?±?1 U, 10?±?1 U, 30?±?1.5 U, 40?±?2 U, 60?±?3 U and 80?±?4 U).  Multiple studies have shown that pens are more accurate than syringe dosing, particularly for small doses, but this variability means that we could routinely be over or underdosing by a significant amount without having any way of knowing.  And pump users can’t consider ourselves immune to this variability. Studies of pump accuracies have shown not only variability of bolus doses, but significant variability of basal delivery with smaller doses having larger margins for error. And the amount of insulin needed to be blocked to set off occlusion alerts means that we really have a lot of room for mathematical error in knowing IOB at any given moment in time.

So if my meter is off by 10%, and my carb count is off by 10%, and my pen or pump is off by 10%, how can we ever hope to manage this disease?

The answer to diabetes management that is stable, steady and in which we can have a level of confidence is patterns. Rather than constant analysis of the movement of every food and dose, we can zoom out and look at patterns. Any single BG carb count or insulin dose may be off, but when we gather the outcomes of many BGs, carb counts and doses over a period of time the variability of these issues become outlyers. We are able to make dosage adjustments, and build habits based on the big picture of statistically significance rather than constantly being tossed about on a sea of variables. When we make micro adjustments day by day we often end up frustrated and exhausted because we end up chasing confounding variables. But slowing down, taking time to se the impact of adjustments over a week or more allows us to make meaningful changes that can reduce the burden of diabetes management both mentally and emotionally.

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