There are many ways to dose mealtime insulin. One way, called matching insulin to carbohydrate or advanced carb counting, involves the use of two ratios. One ratio tells you how much insulin you need for a given amount of carbohydrate and the other ratio tells you how many points one unit of insulin will drop your blood glucose.

You might have been given the ratios by your health care professional, or maybe you calculated your ratio from an equation, or you could have completed a series of food and blood glucose records and had the ratios calculated from the information in these notes. If your ratios were calculated a long time ago, how do you know that they are still adequate and, even more importantly, how do you change them if they are not?

There is a simple way to determine if your ratios are doing their jobs. In addition to the two ratios, you were most likely also given a blood glucose target or goal to aim for—somewhere between 100mg/dl and 150mg/dl. The lower end of the range is often used for young, healthy adults and pregnant women who want tight control of their blood glucose, while the higher range may be used for those who are at risk for frequent episodes of hypoglycemia.

If your ratios are on target, your blood glucose three hours after injecting insulin should be within a 40 point range from your goal number. For example, let’s say you are using a correction factor of 50. This would mean that each unit of insulin would drop your blood glucose 50 points. If your target blood glucose was 100 mg/dl, then, if your ratios are accurate, your glucose level three hours after a correction dose should be between 60 mg/dl and 140mg/dl. But keep in mind that 60mg/dl is a low reading and if your glucose level is often in this range after you take a correction dose, it is likely that your correction factor is too strong.

When you check your correction factor you should make sure your blood glucose is above 180mg/dl, that you are not having anything to eat or drink and that you were not recently physically active. If you are also evaluating your carbohydrate ratio you want to make sure your blood glucose is in target range before you eat so you don’t have to give a correction, that you know the specific grams of carbohydrate in the meal and that your meal is low in fat and doesn’t contain alcohol.

If, when testing your correction factor you land outside of your target zone on two or more occasions, a modification of your correction factor would be in order. To do this you would subtract your current blood glucose level from your starting blood glucose level and then divide the number of insulin units taken into the result.

Here’s an example: Starting blood glucose = 300, ending blood glucose = 200. The correction reduced your glucose level by 100 points. If you took 5 units of insulin, your correction factor would be 20 (300-200=100/5 =20), if you took 10 units it would be 10.

Knowing how your correction factor works and being able to adjust it when life changes can keep you ahead of the curve in your diabetes management.

Hi,

I didn’t know the formula to adjust the correcting factor and it’s very useful.

Thank you very much.

Cristina

I am a 30 year old type 1 and have been diabetic since I was 20. I consistently have A1c results in the low sixes. I attribute almost all of that success to knowing my ratios of my Lantus and Novolog and specifically using the concepts outlined here. . . rather I should say understanding how to calculate new ratios for myself when I’m not getting glucose readings between 80-120.

I understand that these treatment procedures are really difficult and complicated for many people, especially if math and numbers are a challenge, but I have a background in Finance and business analysis so I was fortunate enough to find this straightforward and logical.

I would urge those that take a less tailored and analytical approach to really put forth the effort with your doctor to understand how to do this method here because all those years of cumulative lower glucose levels will be truly a a lifechanger.

I would just like to add one thing. Please make sure to have 2 or 3 different corrective ratios and mealtime carb ratios to use throughout your day. Because I am so insulin resistant in the morning (or start of my day) that it is almost twice what I use later on in the day. And when it comes to my corrective ratio, I need 4 or 5 units to drop me 100 points at the beginning of the day and only 1 unit to drop me 100 points thereafter. So please don’t be confused if you’re trying to use 1 standard ratio to get you through everything. Make morning, lunch, and dinner ratios.

Dear CBS,

Many people do end up needing more than one insulin to carb ratio during the day. It can be due to greater insulin resistance at a particular time of the day or simply because their eating patterns, e.g. higher in fat at dinner, change at different meals. The best thing to do is to start with one ratio and self-monitor to see what your blood glucose levels are 2 to 3 hours are after different meals.

In the formula: 300-200=100/5 =20, I understand that 20 is the correction factor, but what does 20 stand for, units of insulin??!!!

With all do respect, I think there´s something wrong with your formula. Assuming that the target glucose level is 100. The patient took 5 units of insulin that reduced 100 points of glucose level (from 300 to 200), then the patient would need 10 units to reduce 200 points (from 300 to 100). If he/she took 20 units of e.g. humalog, he would be dead in 3 hours.

Dear Mary,

The example in the blog concerns a correction factor that didn’t work. It reduced the glucose level to only 200 mg/dl and didn’t bring it to target. Five units of insulin were taken, therefore the correction factor( or drop in blood glucose) per unit of insulin is 20. Every unit brings the blood glucose down 20 points. It that is so and the target is 120, 9 units of insulin are needed; if the target is 100, 10 units of insulin are needed.

CBS – Your comments were as helpful as the article. I was diagnosed with Type I at 50 and I my endocrinologist said that I am just about the most brittle diabetic he has ever seen. Using different ratios during the day may help me. Would you please walk me through your system? If you contact me at mcerreto@aol..com, we could set up a time to talk. Thank you. Mary Cerreto, Ph.D.

Dear Mary,

In order to see if your correction factor or insulin to carb ratio is working you need to check 3 hours post meals. If the result is greater than 40 points away from your goal and you have checked at least twice then you may need to change the factor. Bringing your records to your diabetes educator can make it clearer for you.

The article was informative relative to those who are on Multidose Injections. Is the approach same for those of us on Insulin Pump Therapy ? I would greatly appreciate additional info. on this. I have been on insulin pump for 25 yrs and aTD1 since 3y/o. with great HgbA1C -6.2-6.6 and a nurse. Many thanks !