Carb- Insulin Ratios


What carb-insulin ratios do people use? I’ve gotta work it out. At the moment I’m guestimating… made worse by not measuring carbs accurately. Bad me!

I know I need much more insulin (bolus) in the mornings (even 20 g of carbs in the morning without short acting insulin can send me high) than lunchtime. But in the evenings I can eat a some more carbs (20 - 30 g) without needing extra insulin at all.

Currently I use 10 units morning and evening of NPH, and I guess and inject novalog before meals where I eat carbs. I’ve only gone low once (60s) so far when I injected Novalog for a carby evening meal. Now I try to avoid many carbs and insulin in the evenings.

I pretty much use about an ICR of 4. I am a bit insulin resistant. I rarely eat meals with more than about 30 g carbs.

It’s hard to set i:c ratios if your basal insulin is not providing reliably in-target blood glucoses over the 24 hour period, and with NPH you don’t get that. That being said, you’ll have to do it trial and error. Keep a small notebook with times and test results at left, what you ate with grams in the middle, and what NPH and Novolog units you gave.
Use small numbers of carb grams and small numbers of Novolog first, figuring how far up a 4 gram tablet of glucose takes you. When you’re 160-180 mg/dL, you can inject one unit Novolog to see your sensitivity - how far down one unit will take you. You’ll have to do this for each third of the day since your NPH varies your baseline instead of being able to depend on always starting from a blood glucose of approximately 100 mg/dL.
You’ll also need to see how far up small numbers of starch, milk products, and fruit take you separately, since each affects your blood glucose differently. Note how fast each works - and with pizza, note you’ll need an immediate injection plus a later one in 3 hours.
If able to move from NPH to an 18-24 hour basal insulin, do so. The basal insulins sometimes require two shots a day due to spikes and length of action varies with individuals, but you can get a more stable round-the-clock baseline with them - then i:C ratios become more stable to figure, too.
Everyone uses a greater amount of insulin per carb in the a.m. than noon and supper, due to tamping down Dawn Phenomenon.
Newbies usually start with ratios 1unit:15gm and do trial and error from that, but with NPH as your basal, I can’t predict.
I’m on 1:3 in the morning; 1:4.5 noon and supper. I’m taking prednisone so that skews my regular i:C ratio mammothly! Good luck, best wishes, etc.

I am 1:10 in the mornings, 1:15 in the afternoon, and I can sometimes even get away with 1:20 in the evenings. Most people are more insulin resistant in the morning because of the hormonal surge we all have upon waking first thing in the day. I am fairly insulin sensitive and very active, so my I:C ratios may be a bit higher than most. I try to keep all my meals around 30-40g of carbs, less if possible.

I agree that you’ll need to make sure that your basal insulin is keeping you steady first in order to get a good idea of what your carb ratio should be. I use 1 unit for every 6 grams of carbs in the morning and then 1 for every 8 the rest of the day. I think everybodies carb ratios vary quite a bit, and you’ll just have to experiment to figure out what works well for you! Good luck!

Mine varies between 1:8 and 1:12, depending on where I am in my monthly cycle. It’s currently at 1:12.

When I am exercising regularly (I’m currently not exercising at all) that puts it up to 1:14 or 1:15.

If I lost weight (I’m currently overweight), it would probably go down a bit more.

I agree that it’s hard to work out an I:C ratio with NPH. I tried it back when I was on NPH and none of it made any sense until I started Lantus.

I currently use 1:15 for breakfast and lunch and 1:18 for dinner.

It was definitely trial and error figuring this out and will be quite different for most people.

As others have said, lots of trial and error is involved, and I know for me, once I have my ratios all set, something happens & I need to start tweaking again. Right now, I’m at 1:27 i:c from 5:30am-8am, and the rest of the time it’s 1:45. My correction ratio is a round the clock 1:60.

Saw my endo and my latest A1c was 7.0. Not that great. She said to switch my ratio to 1:15 and Lantus 13. That was only up one unit for each. i kept getting over 200 after eating so I changed my ratio to 1:5 for breakfast and 1:10 the rest of the day and Lantus 14. I like my doctor but think she is way too conservative. Now my after meals are closer to 150. Still I may have to play with it a little more.

I usually do OK with 1 unit for 8g of carbs. If I’m more active than usual, I can go with 1:10.