Carb Counting and Math | QoW Rationale

Our May 19th Question of the week was a question about carb counting. Although 58% of respondents chose the correct answer, 42% did not. We thought that this was an important topic to discuss further, so we can pass on correct info to people living with diabetes.

Before we start though, if you don’t want any spoilers and haven’t tried the question yet, you can answer below: Answer Question

Question: LS uses an insulin pump and the 500 rule for carbohydrate coverage. For breakfast, LS plans to eat ½ cup of oatmeal, 3/4 cup of blueberries, a cup of skim milk, a tablespoon of peanut butter, and a cup of coffee with a packet of Splenda. Her insulin to carb ratio is 1 to 12 for breakfast and lunch. Her insulin to carb ratio is 1 to 15 for dinner. 

How much insulin does LS need for breakfast?

Answer Choices:

  1. 3.0 units
  2. 2.8 units
  3. 4.0 units
  4. 3.5 units

This image has an empty alt attribute; its file name is Q1-5_19-1.png

As shown above, the most common choice was option 4, the second most common answer was option 3 then option 1 and finally option 2.

This image has an empty alt attribute; its file name is Capture6.png

Answer 1 is incorrect. 14% chose 3.0 units as the answer. This answer was juicy but wrong. Maybe this group thought the total carb count was 45 gms and then divided by insulin to carb ratio of 1:15? If yes, read the question again to see what insulin to carb ratio is a better choice. Also, rethink the total carb count.

Answer 2 is incorrect. Only 8% of respondents chose 2.8 units as an answer. This group got the carb count correct but may want to read the question again to see which insulin to carb ratio is a better choice.

Answer 3 is also incorrect. About 20% of respondents chose 4.0 units. This group might need to reassess the carb count, keeping in mind that milk is 12gms of carb. And, more importantly, keep in mind that LS uses an insulin pump that can deliver very precise insulin doses. No need to round up for this question.

Finally, Answer 4 is correct. 58% of test takers chose this correct answer.

First, lets count up the carbs for breakfast:

  • ½ cup of oatmeal = 15 gms
  • 3/4 cup of blueberries = 15 gms
  • A cup of skim milk = 12 gms
  • A tablespoon of peanut butter – 0 gms
  • Cup of coffee with a packet of Splenda – 0 gms
    Total carbs = 42 gms

Now, let’s do the math:

LS’s insulin to carb ratio is 1 to 12 for breakfast. She is going to eat 42 gms of carb. 42/12 = 3.5 units of insulin to cover breakfast.


We hope you appreciate this week’s rationale! Thank you so much for taking the time to answer our Question of the Week and participate in this fun learning activity!


Join Coach Beverly on February 2, 2021, for her annual
Level 2 – Standards of Care Update!

This course is an essential review for anyone in the field of diabetes. This course summarizes the 2021 updates to the American Diabetes Association’s Standards of Medical Care in Diabetes and provides critical teaching points and content for health care professionals involved in diabetes care and education.

Earn 2.0 CEs and get ready to lead the charge to implement best care practices for the New Year. 

Topics Include:

  • A review of changes and updates to the 2021 ADA Standards of Medical Care
  • Identification of key elements of the position statement
  • Discussion of how diabetes educators can apply this information in their clinical setting

Sign up for Diabetes Blog Bytes – we post one daily Blog Byte from Monday to Friday. And of course, Tuesday is our Question of the Week. It’s Informative and FREE!  Sign up below!


AccreditationDiabetes Education Services is an approved provider by the California Board of Registered Nursing, Provider 12640, and Commission on Dietetic Registration (CDR), Provider DI002. Since these programs are approved by the CDR it satisfies the CE requirements for the CDCES regardless of your profession.*  

The use of DES products does not guarantee the successful passage of the CDCES exam. CBDCE does not endorse any preparatory or review materials for the CDCES exam, except for those published by CBDCE.