Something to think about

A. Let's assume your insulin to carb ratio is, for example, 1 unit of insulin for every 10 grams of carbs.
   This is the number which is programmed into your pump to determine boluses for meals.

B. Let's also assume that your sensitivity in 30 mg/Dl for every unit of insulin.  That is, 1 unit of insulin will
   drop your blood sugar 30 points (mg/dL).  This is the number which is programmed into your pump
   for correction boluses.

IF 1 unit of insulin equals BOTH A. 10 grams of carbs AND B. 30 blood sugar points (mg/dL) THEN
    A. 10 grams of carbs equals  B. 30 blood sugar points (mg/dL) which simplifies as follows:
          1 gram carbs = 3 sugar points (mg/dL)

In theory at least, what this implies is that for every one gram of carbs you eat without bolusing or, morelikely, to correct a low, your sugar should go up 3 points.  You can use this information in the following way:

EXAMPLE:  Say you just woke up with a 52 blood sugar and you want to ingest the exact amount of carbs to raise your blood sugar to 100.  To figure it you would divide the difference between the two, 48, by 3, which is the number of sugar points you should get out of 1 carb ingested and get exactly 16
grams of carbs.  Since most glucose tablets contain 4 grams of carbs, you would need to take exactly
4 glucose tablets.  It also means that every single glucose tablet would raise YOUR glucose by 12 points.

You might ask, what if I do the calculations, try it and it doesn't work out that way.  What does it mean?
It probably means that either you carb ratio or insulin sensitivity settings or both are incorrect.  Now this is interesting because it gives you a very easy way to recalculate all three numbers.  You would have to start with at least five hours of fasting, no exercise and a blood sugar of around 150.  First, take 1 unit of insulin, wait a couple of hours, and see how far your sugar drops.  This will give you your sensitivity. Now eat 2 or 3 standard glucose tablets, wait an hour more, and see how far your sugar rises.

To find your carb ratio, first divide the number of points your sugar rose after eating the tablets by the total number of carb grams in the tablets.  Then divide your insulin sensitivity, which is the number of points your sugar DROPPED after taking the insulin, by the first number to get your carb ratio.

EXAMPLE:  You tested your blood sugar, after fasting and no exercise, and it was 150.  A couple of hours  after taking exactly 1 unit of insulin your sugar dropped to 112.  This tells you your sensitivity is the difference between 150 and 112, or 38. Next, an hour after eating exactly 2 glucose tablets (8 grams of carbs) your sugar rose from 112 to 144.  So you divide the difference between 144 and 112, which is 32, by the 8 grams of carbs to get 4,  Next you divide your sensitivity, 38, by 4 and get 9.5, which is your carb ratio.  You should need 1 unit of insulin for every 9.5 grams of carbs you eat.

Simple huh?

you lost be in section A.



Wow, I'm proud of myself for reading all your calculations. (:

You better hope you're not getting a cold or something! I feel like my body doesn't stay that consistent throughout each month. It depends on stress, illnesses, hormones, etc. I've always wondered if it's easier for guys to keep consistent blood sugars because they don't have to worry about adjusting insulin up and down for menstrual cycles. lol.

I understand everything you've said but how do you factor in the basal rates?  Or rather the possibility of your basal rate being a little too high or too low?


Hi Jaco1199,

Yes, you couldn't factor in your basal rates being too high or too low UNLESS you knew EXACTLY how much too high or too low.  In which case, you would have or at least will correct your basal rate.  This is why establishing correct basal rates throughout the day and perhaps even basal patterns for different kinds of days (eg. work days, exercise days, etc.) MUST come first.  Basal rates, as I'm sure you know, are determined by fasting for different time periods throughout the day.

My initial intent on writing this post had been to establish the 3-way connection between carb-insulin ratio, insulin sensitivity and the one most people don't think of which is, carb-blood sugar ratio.  This last one is the one which SHOULD tell you exactly how many carbs to eat (or drink) when your sugar is low to bring it up to your target blood sugar.  I have found over the past few days that glucose tablets are not doing what I expect them to do, so I'm beginning to investigate.

I'll agree that the carb-blood sugar ratio is important and one that not too many people think about only because when you're low you just want to get your sugar up and will grab/eat anything.  I am at major fault for this (especially for a night time low).  Then I have to deal with the high blood sugar later on.  And it's that up and down that really wears me out. It's all such an intricate balancing act.  

Since the carb ratio can change throughout the day and sensitivity can change throughout the day I guess the carb-blood ratio will change throughout the day also.  Which is something I've never factored in - I'll have to try it.  Hopefully it'll help with some of my rebounding frustrations.   

Wouldn't it be nice if it was that easy? But you can't just use a mathematical model like that, with experimentation, for a few reasons.  How can you be sure that your basal rates are right, or know how much they are wrong, if you're other stuff isn't perfect?  How do you get rid of other factors like mood, hormonal cycle, activity level of that day and all of the previous days, how long you were awake for, etc?  They're all going to have an impact, and it's all going to be a bit messed up by the fact that you have to start with at least five hours of fasting.  Have you heard of the morning effect that makes it so that people need more insulin in general in the morning?  I've also found that my sensitivity varies by different times of day.

You have a nice theory, and if it works for you then that's great.  But there are other ways to do it, and they're less intrusive.  For example, you can chart your numbers and see when you're going high.  If you spike a little after meals and don't drop right back down, then you need more meal bolus.  If you're too high in general for a while, you need more basal.  It's trial and error and adjustment.