How do you determine your insulin to carb ratio?

When I started using the Omnipod, my instructions were to bolus 5.5 + the 1 unit correction bolus before meals. So I have not had to deal with figuring out my carb:insulin ratio. Can someone tell me how you figure out what your carb to insulin ratio is?


What is your sensitivity factor? For example 1 u of insulin drops you x amount of points in BG. I am not 100% positive on this, but a good place to start is to do 1/4 of your sensitivity factor. So, for example, if your sensitivity factor was 1:40 (meaning that you dropped 40 mg/dl with 1 u of insulin) then a good place to start for your I:C ratio would be 1:10 (1 unit of insulin for every 10 g of carbohydrates). This is again a starting point and you may need more or less depending…
Because you’re a type II, it may also be different for you (although I am not sure to what extent).

One other point I might mention is that throughout the day my I:C changes (I have a lower ratio in the morning b/c of insulin resistance) so my sensitivity factor is also lower (1 u doesn’t drop me as much). Later in the day both of these increase some as my body becomes more insulin sensitive.

Thanks, Bradford.

I have abosolutely no idea what my sensitivity factor is, unfortunately. I’m a complete novice with all of this and my trainer just said to do a 5.5 unit bolus with meals, plus one unit for each 50 points above 150 before meals since I don’t use a count of carbs to determine my bolus dose. For snacks, just 5.5 units. I end up bolusing every 2 to 3 hours.

My basal rates were recently increased, since the rates I started at weren’t quite getting the job done and I’d end up adding 3 correction units to my meal boluses every meal.Talk about insulin resistance! My cells will fistfight the insulin to keep it out. I am on U500 because it takes 200 units of U100 each day to keep my BG below 225.

Now my BG generally is between 120 and 180 with occasional spikes in the 200’s. Not nearly like before when getting below 250 was a major fete.

Any help, advice, links to more information, is extremely welcome.


I highly HIGHLY recommend the book “Pumping Insulin” by John Walsh. He takes you step by step in figuring out how to start from a baseline with your ratio (and other settings) based on age/weight/etc and then teaches how to adjust. The book came out long after I started pumping, so I haven’t used it that much, but when I checked what I was already doing (and what was working well for me at the time) against his precise instructions, I was really impressed that he was right on the mark.

Maybe try a quick phone call to your trainer or doctor, maybe they have that information figured out and forgot to share it with you.

Are your meals and snacks pretty consistent with the number of carbs? If you keep track of the number of carbs consumed (which really is necessary when using insulin to carb ratios), 5.5 units, and a good post meal blood sugar, then you could do some reverse math (5.5 units, pre meal blood sugar 120, carbs eaten - 60, post meal 118, so, 5.5 units worked well with 60 carbs, divide 60 by 5.5 and you get about 1 unit for every 11 carbs)

Your suggestions make perfect sense. Thanks!

I found Pumping Insulin on Amazon last night and will be ordering it this weekend. Thanks Melissa!


Since you’re using U500, things may be different for you. I’ve heard/read that U500 acts more like NPH than one of the rapid-acting insulins, so you may not be able to use a strict I:C ratio. I would suggest doing lots of research online to find others using U500 like you are. There are some on the ADA forum boards who use it - I think their activity is mostly on the Type 2 boards.

Thanks Kimberly. If I remember correctly, because I am using the U500 (regular) insulin, instead of fast acting insulin, they put me on the 5.5 dose bolus dose. I’ll look into it.