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Carbs Content Alone Not Enough for Insulin Calculations

Mar 2, 2019
Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Dahlia Elimairi, Pharm D student at UC Denver Skaggs School of Pharmacy

New evidence suggests added consideration of the protein and fat.

People with type 1 diabetes who are calculating pre-meal insulin dose are usually only advised to count the carbohydrate content of a meal, and while this improves glycemic management, there is increasing evidence to suggest that protein and fat should also be considered when calculating pre-meal insulin dose.

The effect of protein on glucose levels has not been studied as extensively as have the effects of carbohydrates on glucose levels. But with the limited amount of evidence available, protein in diet has shown to cause a delayed and prolonged rise in postprandial glucose levels. The mechanism by which it does this is still not fully understood, but some proposed mechanisms include dysregulated glucagon release and gluconeogenesis in the absence of adequate circulating insulin. Consumption of dietary protein results in an increase in amino acid availability, which can be converted into glucose through gluconeogenesis. Gluconeogenesis occurs in the presence of glucagon, and meals high in dietary protein have been shown to increase glucagon secretion.

A new randomized crossover trial conducted in two pediatric centers in Australia aimed to quantify the insulin requirement for a high-protein meal compared with a low-protein meal, controlling for carbohydrate and fat content.

A total of 11 participants were randomized to consume a high- (60 g) or low-protein meal (5 g), each containing 30 g carbohydrate and 8 g fat. A variation of the insulin clamp technique was used to determine the insulin requirements to maintain euglycemia for the following 5 hours. The quantity of protein provided in the high-protein meal was representative of the quantity consumed in regular meals by adolescents with type 1 diabetes.

The mean glucose levels for both interventions prior to meal consumption were similar. The mean insulin requirements for the high-protein meal were higher than for the low-protein meal, with inter-individual requirements ranging from 0.9 to 6 times the low-protein meal requirement. Approximately half the additional insulin, 1.1 units/h was given in the first 2 hours, compared with an additional 0.5 units/h in the second 2 hours and 0.1 units in the final hour.

The study concluded that on average, the high-protein meal required 3.6 more units or 54% more intravenous insulin than the low-protein meal in the 5-hour postprandial period. Most insulin is required within the first 2 hours and inter-individual differences exist in insulin requirements for dietary protein.

Previous articles have also studied this concept and came to similar conclusions.

A study by MA Paterson determined the effects of protein alone (independent of fat and carbohydrate) on postprandial glycemia in individuals with type 1 diabetes using intensive insulin therapy. Seventy-five grams or more of protein alone significantly increased postprandial glycemia from 3 to 5 hours in people with type 1 diabetes using intensive insulin therapy. The glycemic profiles resulting from high-protein loads differed significantly from the excursion from glucose in terms of time to peak glucose and duration of the glycemic excursion. This research supports recommendations for insulin dosing for large amounts of protein.

Another study by CE Smart assessed the separate and combined effects of high-protein and high-fat meals, with the same carbohydrate content, on postprandial glycemia in children using intensive insulin therapy. The study concluded that meals high in protein or fat increase glucose excursions in youth using intensive insulin therapy from 3 hours to 5 hours post meal. Protein and fat had an additive impact on the delayed postprandial glycemic rise. Protein had a protective effect on the development of hypoglycemia.

Further research is required before the development of definitive recommendations around the optimal timing of insulin delivery to manage high-protein meals.

Practice Pearls:

  • There is rising evidence that protein should be considered in the calculation of pre-meal insulin dose.
  • Most studies suggest that most of the insulin is needed in the first 2 hours to prevent glycemic rises for meals containing carbohydrate and protein, and that most of the additional insulin must be given within the first 2 hours to prevent the rise after protein consumption that begins 90–120 min after the meal.
  • Inter-individual differences exist in insulin requirements for dietary protein.


Evans M, Smart CEM, Paramalingam N, Smith G, Jones TW, King BR, Davis EA. Dietary protein affects both the dose and pattern of insulin delivery required to achieve postprandial euglycaemia in Type 1 diabetes: a randomized trial. Diabet Med. 2018 Dec 7.

Calbet JA, MacLean DA. Plasma glucagon and insulin responses depend on the rate of appearance of amino acids after ingestion of different protein solutions in humans. J Nutr 2002; 132:2174–2182.

Paterson MA, Smart CE, Lopez PE, McElduff P, Attia J, Morbey C, King BR. Influence of dietary protein on postprandial blood glucose levels in individuals with Type 1 diabetes mellitus using intensive insulin therapy. Diabet Med. 2016 May;33(5):592-8.

Smart CE, Evans M, O’Connell SM, McElduff P, Lopez PE, Jones TW, Davis EA, King BR. Both dietary protein and fat increase postprandial glucose excursions in children with type 1 diabetes, and the effect is additive. Diabetes Care. 2013 Dec;36(12):3897-902.

Dahlia Elimairi, Pharm D student at UC Denver Skaggs School of Pharmacy