Blood Sugar Management: Insulin-to-Carb Ratio or Fixed-Carb Diet?

People living with type 1 diabetes (T1D) need to manage their blood sugars, and the best way to do that is to balance their carb and insulin intake. They generally use one of the following two methods: 

  • Fixed carb amount and insulin dose: The number of carbs to consume and the insulin dose to inject for each meal are predetermined, e.g., 60 grams of carbs for breakfast, every day. Those who are not yet comfortable with the insulin-to-carb ratio usually follow this method.
  • Insulin-to-carb ratio (I:C ratio), a.k.a. “carb counting”: Insulin needs for 10 grams of carbs (“x” insulin unit(s)/10 grams of carbs) or the number of carbs for one insulin unit (“x” grams of carbs/1 insulin unit) are predetermined. This method allows more flexibility and a broader array of food choices, but is also more complex and requires practice.  

Some benefits of the I:C ratio method shown in several studies 

French researchers recently followed two groups of children with T1D for a year. The first group used the method with fixed carb amounts and insulin doses, and the second group used the I:C ratio method. 

In a series of questionnaires aimed at evaluating participants’ quality of life, the second group scored higher. 

However, it’s important to mention that while the I:C ratio method has some benefits for quality of life, its continuous use seems to be more challenging, because not all participants were able to maintain this blood sugar management method. At the start of the year-long observation period, 85% of the second group used the I:C ratio method for at least three out of four meals. At the end of the period, this percentage had fallen to 65%. 

Which method is best for blood sugar control?

The risks of hypoglycemia and diabetic ketoacidosis remained the same for both groups during the entire year-long observation period.

Three months in, the I:C ratio method group saw a significant improvement (~0.3% decrease) in their hemoglobin A1c (HbA1c). After those first three months, the gap shrunk and both groups’ average HbA1c was similar. This could be due to how difficult it is to continuously keep using the I:C ratio method. It is therefore essential to set goals with your healthcare team to achieve the potential benefits of the I:C ratio method.

The BETTER team wants to analyze which eating patterns are best for improving blood sugar management.

If you or your child are living with type 1 diabetes in Quebec, sign up for the BETTER registry!


  • Donzeau, A., Bonnemaison, E., Vautier, V., Menut, V., et al. (2020). Effects of Advanced Carbohydrate Counting on Glucose Control and Quality of Life in Children with Type 1 Diabetes. Pediatric Diabetes. doi:10.1111/pedi.13076
  • Vaz, E. C., Porfírio, G. J., Nunes, H. R., Nunes-Nogueira, V. D. (2018). Effectiveness and safety of carbohydrate counting in the management of adult patients with type 1 diabetes mellitus: A systematic review and meta-analysis. Archives of Endocrinology and Metabolism. doi:10.20945/2359-3997000000045

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