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Calculate Insulin Dose: An Updated Guide

Living with diabetes is not easy. For some people with diabetes it is necessary to calculate insulin doses, which can help maintain good blood sugar control. 

The different types of insulin’s on the market are rapid acting, short acting, intermediate acting, long acting and fixed combinations. This article will focus on exploring the difference between basal insulin and bolus insulin. Examples will be given on how to calculate an insulin dose if the meal is high in carbohydrates, high in fat, or high in fat and protein.

To understand if you are calculating insulin properly, a brief chart will review normal blood sugar levels. Another chart will review symptoms of low blood sugar and high blood sugar.

Anyone who needs to understand how to calculate an insulin dose should continue reading.

Types of Insulin  

A picture of insulin and a syringe

Basal  Insulin 

Basal Insulin provides the body with a small, steady amount of insulin for the body’s daily needs. It is a long acting insulin (1). Usually the dosage for this type of insulin is set up by the endocrinologist. Though if you feel the dosage needs to be changed then please contact your endocrinologist.

Bolus Insulin 

Insulin injected in a bolus or larger quantity before meal times and snacks are usually rapid acting insulin. These insulin types begin working 5-15 minutes after they have been injected or bolused into the body (1).

Calculating Insulin Dose

To calculate an insulin dose you need to understand your insulin to carbohydrate ratio. This number will tell you how much 1 unit of insulin can handle moving carbohydrates into the cells of your body. A 1:10 ratio means that 1 unit of insulin can move 10gm of carbohydrates into the cells while a 1:30 ratio means that 1 unit of insulin can move 30gm of carbohydrates into the cells.

Correction Dose 

A correction dose is used to bring insulin levels down

A correction dose of insulin is affected by how sensitive a person is to insulin. When correcting for high blood sugar, a unit of insulin can drop blood sugar by 30-100mg/dl. At mealtimes, add a correction insulin dose to mealtime insulin with initial bolus.  

High Fat Meal

Any meal with 30gm or more of fat can increase insulin resistance and cause hyperglycemia 2-3 hours after a meal. 

Current research suggests to initially add 30% insulin to a high fat meal and splitting the dose in two by 50%. Then administer the other 50% of the insulin dose 1-2 hours after the meal. Adjust as needed to optimize blood sugar results.

High Protein Meal

A meal with 75gm of protein or more may increase blood sugar levels 2-3 hours after a meal and could cause hypoglycemia within the first hour after the meal. While a meal with 20-50gm carbohydrates does not significantly affect blood sugar levels.

 Monitor blood glucose levels and correct as needed. Calculate insulin dose based on carbohydrates eaten.

High Fat/High Protein 

For meals with over 30g fat and over 25gm protein, blood sugar can rise 2-3 hours after the meal.

Calculate insulin dose based on carbohydrates eaten. Then 1-2 hours after the meal consider adding an additional 15%-40% insulin.

Examples:

Example 1: High Carbohydrate Meal

50gm carbohydrates, low in fat and protein, Insulin/Carb ratio (ICR) = 10

50gm carbs divided by 10 (ICR) = 5 units of insulin

Bolus/Inject 5 units of insulin 15 minutes before the meal

 Example 2: High Fat Meal 

60gm carbohydrates, 30gm fat and moderate protein, ICR=15

60gm carbs divided by 15 (ICR) = 4 units of insulin 

Add 30% more to 4 units of insulin calculated: 0.3×4 = 1.2 units insulin 

Add 1.2 units to 4 units mealtime insulin dose: 4+1.2 = 5.2 units insulin  

 Divide total insulin need for meal (5.2 units insulin) by 50% or half of the insulin calculated: 5.2  divided by 2 = 2.6 units insulin   

Bolus or inject 2.6 units insulin 15 minutes before the meal and then another bolus or inject another 2.6 units insulin 2-3 hours after the meal.   

Example 3: High Protein/High Fat Meal 

>50gm protein, 40gm carbohydrates, >30gm fat, ICR=20

40gm carbs divided by 20 (ICR) = 2 units of insulin

Calculate 15%-40% insulin: 0.25 (25%) x 2 = 0.5 units insulin   

Bolus 2 units insulin 15 minutes before the meal  

Bolus 0.5 units insulin 1-2 hours after the meal

Insulin Level Graph
Low<70mg/dL
Fasting70-130mg/dL
After Meals: 2-3 hours180mg/dL
High>200mg/dL

Hypoglycemia (Low Blood Sugar)

Picture of a woman who is having trouble concentrating

Symptoms 

ShakinessRapid Heart Rate 
Trouble Concentrating Fatigue 
Sweating Dizziness
Blurry Vision Nausea 

Corrective Action

  •  51-70mg/dL- Consume 15gm of carbohydrates 
    • Repeat if not in range after 15 minutes.  
  • <50mg/DL – Consume 20-30gm of carbohydrates 
    • Repeat if not in range after 15 minutes.

Hyperglycemia (High Blood Sugar) 

picture of a girl who is angry

 Symptoms

Frequently ThirstyWeight Loss
Excessive Urination Fatigue
Blurred Vision Delayed Healing 
Increased AppetiteIrritability 

Corrective Actions 

  • Exercise ideally for ~30-60 minutes 
  • Take the diabetes medication prescribed by your doctor
    • 1 unit of insulin decreases blood sugar by ~30-100mg/dL
  • Modify diet to include less refined carbohydrates and less fat in foods

Conclusion 

Use long acting (basal) insulin for everyday cellular needs and rapid acting insulin for mealtime bolus. When the blood sugar is elevated before a meal, add extra insulin to mealtime bolus to bring excessive blood sugar down.   

Carbohydrates elevate blood sugar levels. Fats delay blood sugar from entering into the blood and can cause delayed high blood sugars. Excessive protein can also cause delayed high blood sugar levels. Calculate insulin dose using the suggested guidelines as a base to understand your unique insulin needs around mealtimes. Download your guide to calculating insulin dose to make it easier for you.      

Monitor any undesirable symptoms of either low blood sugar levels or high blood sugar levels. You can do this!

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