The relationship between carbohydrate and the mealtime insulin dose in type 1 diabetes

J Diabetes Complications. 2015 Nov-Dec;29(8):1323-9. doi: 10.1016/j.jdiacomp.2015.08.014. Epub 2015 Aug 20.


A primary focus of the nutritional management of type 1 diabetes has been on matching prandial insulin therapy with carbohydrate amount consumed. Different methods exist to quantify carbohydrate including counting in one gram increments, 10g portions or 15g exchanges. Clinicians have assumed that counting in one gram increments is necessary to precisely dose insulin and optimize postprandial control. Carbohydrate estimations in portions or exchanges have been thought of as inadequate because they may result in less precise matching of insulin dose to carbohydrate amount. However, studies examining the impact of errors in carbohydrate quantification on postprandial glycemia challenge this commonly held view. In addition it has been found that a single mealtime bolus of insulin can cover a range of carbohydrate intake without deterioration in postprandial control. Furthermore, limitations exist in the accuracy of the nutrition information panel on a food label. This article reviews the relationship between carbohydrate quantity and insulin dose, highlighting limitations in the evidence for a linear association. These insights have significant implications for patient education and mealtime insulin dose calculations.

Keywords: Carbohydrate; Carbohydrate-to-insulin ratio; Insulin; Postprandial glycemia; Type 1 diabetes.

Publication types

  • Review

MeSH terms

  • Combined Modality Therapy / adverse effects
  • Diabetes Mellitus, Type 1 / blood
  • Diabetes Mellitus, Type 1 / diet therapy
  • Diabetes Mellitus, Type 1 / drug therapy*
  • Diet, Diabetic
  • Dietary Carbohydrates / adverse effects*
  • Glycated Hemoglobin / analysis
  • Glycemic Index
  • Glycemic Load
  • Humans
  • Hyperglycemia / etiology
  • Hyperglycemia / prevention & control*
  • Hypoglycemia / chemically induced
  • Hypoglycemia / prevention & control*
  • Hypoglycemic Agents / administration & dosage*
  • Hypoglycemic Agents / adverse effects
  • Hypoglycemic Agents / therapeutic use
  • Insulin / administration & dosage*
  • Insulin / adverse effects
  • Insulin / therapeutic use
  • Meals
  • Patient Compliance


  • Dietary Carbohydrates
  • Glycated Hemoglobin A
  • Hypoglycemic Agents
  • Insulin
  • hemoglobin A1c protein, human