How do you calculate your I:C ratio


So I have been trying to calculate my Insulin to Carb ratio and not having much success, yet.

I have tried the 500 formula, which doesn’t work at all for me.
I have tried my carbs ÷ daily insulin, and its not right either, closer but not.

I just don’t seem to find how several people can turn around and say my morning I:C is 1:12 and my afternoon is 1:15 and be so exact when I can’t even find an approximate I:C that work for me.

I’m sure it doesn’t help that my sugar is all over the place in the last few days.
For example today’s lunch, I calculated appx 1:15 for my food, and at dinner time I was at 200 (4hrs+later)
Dinner, I used 1:25 ( I know with that dinner, I don’t need much insulin) and used just one unit to help correct my high, and an hour later I was already below 100, two hours later I was nearing 70, so I ate a cupcake and now at bedtime I’m at 115.
I can’t seem to get a good grasp and it’s a lot of guessing based on what I have learned ( more insulin resistance in the morning, more active during the day more insulin sensitive later on etc

My fingers are getting tired of all that testing ( yes, hopefully my insurance will approve a CGM at some point, but it’s not gonna be any time soon).

(joe) #2

@Emet hi Loica,

you start out by adjusting your basal insulin (or basal rates if you pump) because if basal is off then everything is off.

Then at breakfast time, starting with in-range blood glucose, you eat 15-30 grams of fast carbs or the carbs you most typically eat at breakfast. (this is important because different glycemic index foods will mess this test up). You start off with 1:15 and inject your insulin, ideally 15 minutes before you eat, then you test every hour. at 2 hours “post-prandial” (after your first bite) your blood sugar should be no more than 50 mg/dl higher than your pre meal. at 4 hours you should be “exactly” where you started. if you are way off (say +150) then you know you were too conservative, and repeat your test when the conditions are right at 1:12 or 1:10 or some other factor. oh, make sure you activity level is “typical” or you have to go back to start, do not pass Go and do not collect $100.

rinse and repeat for lunch and dinner.

in 3 short months or so, depending on how good your basal adjustments go… you’ll have pretty good numbers for breakfast lunch and dinner.! easy-peasy. think of it as a “lab” and take good notes. yes I am being sarcastic because this sucks so much.

basal adjustments are made by skipping meals in a successive and organized manner and watching for rising or dropping blood sugar. adjustments are made and tests are repeated until you break a window or find you are “good enough”

these “protocols” are in the books “pumping insulin” and “Think like a pancreas”


Thank you @joe
One more reason for me to get these books. Can’t wait to read them.
I’m work on that as per your suggestion.

My basal is good.
At first I was annoyed at my Endo. It took over a month to get my bolus ( between the pharmacy, insurances and doctor, but looking back, it was good as it helped me fine tuned my basal without the ups and downs caused by the bolus.

Now I’m just trying to figure out the bolus.
My schedule and eating habits are very different between the weekend and week days. Weekdays being very active (at work) and limited food intake, so my insulin is very minimal but the weekends with the carbs and the whole schedule being so different, i can get a grasp yet and I figured as I’m on vacation this week and on “weekend schedule” it’d be the perfect time.

Also I’m wondering if our pancreas sometimes pushes out some insulin that can create these huge differences we sometimes experience or does our body “sense” ( for lack of better word) that we have Insulin on board and take a rest from trying to come up with beta cells/insulin ?

Thank you all for being such an amazing support group

(joe) #4

@Emet Hi Loica, first - you’re welcome.

I am assuming you pump - if I am wrong pls let me know.

yup you may have guessed we can’t typically wait around for a doctor to say “nudge your basal rate down at 10 AM” so we need to be very proactive. The more you do it the more comfortable it’ll get.

in honeymoon, yes your pancreas still makes a bit of insulin… it won’t last forever… the next thing to be aware of is your liver will dump sugar from time to time. sometimes when you really need it like when you are going low… other times when it is a pain in the a$$ like early in the morning.

I have my basal and I:C set for my average low activity days… that way when I am in the upper range of activity I can set temporary basals (for a few hours of activity) or a secondary pattern for an all day thing.

my pump lets me schedule I:C based on time of day, so it’s in there, and for me I am more insulin resistant in the morning, so my I:C is set more aggressive for the morning. now if I am headed out on a bike ride right after breakfast… I just override the pump bolus to something more correct for a very active morning.

the thought that the pump is automatic comes with the knowledge that only you know what you are likely to do next… don’t expect that much automation even in a hybrid pump with CGM feedback like the 670. we still have manual transmissions, even with the new bells and whistles! my favorite doctor said to me “you can always take more medicine”.

cheers good luck!


Hi @joe
No I’m not on a pump but on insulin pens for now. Yet I’m learning so much.
His" you can always take more medicine" is so valid.
I started at 1/3 to 1/2 what my Endo prescribed and still going through a lot of hypos, now I’m learning to go even easier and add later if necessary. ( Like last night) This very comment you made to someone else last week hit home for me and has been changing how I’m approaching it.

What I find mess me up in the morning is that my sugar goes up after I wake up. For example, I can wake up and check my sugar and be at 90. An hour or two later, by the time I sit for breakfast I can be at 140. It’s like the dawn phenomenon but awake. Not sure how to handle that either. I try now not to compensate it with insulin because it makes me crash later on. I think it’s once I eat breakfast, it just starts dropping naturally and sometimes pretty fast.

I have also already regained close to 10lbs in the last month alone ( which I wasn’t particularly looking forward to regain) I would really like to find this even keel. Hyper’s make me feel so blahs ( go to bed and not move) and hypos so yuck ( nausea and muscle pain and lost brain cell power)

Am I the only one who also feel like I’m on a rollercoaster when I take insulin. I often feel dizzy and out of sorts shortly after I take it. My numbers are still in the range, but I think it’s just that it’s moving too quickly for my body. Like when you are used to a 15 mph zone and suddenly you are with someone else in the car and they are driving 65 mph in the same zone. I felt that way too when I was on glympiride ( when docs thought I was type 2) I was hoping it would subsidize with time but it hasn’t yet, I’m wondering if it will at some point.

And have a great weekend

(joe) #6

hi @Emet Loica,

hey just one more thought… dawn phenom doesn’t always mean when you are sleeping, the whole thing starts when your liver puts in a little sugar to help you get going in the morning… for normals - it works great, for us, it shows up as a spike.

There are strategies that work… some ignore it until 2 hours after breakfast (that’s what I do) because the breakfast + dawn) is built into my morning bolus, Some eat more, purposely trying to hit ~140 in the morning and find that if they hit it right, it doesn’t appear. keeping with the car analogy: your mileage may vary.

insulin is a growth hormone… if you want to get big, you can take more insulin and eat more carbs… if you want to get smaller, less insulin and less carbs… or less insulin add exercise and same carbs. if you were recently diagnosed, please realize most of the weight you lost was water which is essential.

cheers I will start my great weekend as soon as work is over! - I hope you will too!