Mealtime Insulin Dosing

Medically Reviewed By William C. Lloyd III, MD, FACS
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Mealtime insulin is used to help regulate the normal spike in blood sugar that happens after eating a meal. It can be a gamechanger for people who need extra help keeping blood sugar levels stable.

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When you eat and digest carbohydrates, like bread, chips, corn, and more, they’re converted into a type of sugar that enters your blood stream. Insulin helps to send this sugar from your blood to the rest of your body so it can be used as energy. But people with diabetes don’t make enough or any insulin, and this sugar can sit in their blood and cause big problems. That’s why many people with diabetes must take insulin to cover what they’re missing.

Background insulin (sometimes called basal insulin) is taken once a day and helps your body process the food you eat, but sometimes it’s not enough. That’s when your doctor might prescribe mealtime insulin, which you’ll take before you eat.

Mealtime insulin is used to help regulate the normal spike that occurs in your blood sugar after eating a meal. It can be a gamechanger for many who need extra help keeping blood sugar levels stable. But it can also be intimidating or overwhelming to take, since every dose of mealtime insulin needs to be calculated based on different factors. However, with the right information and a little practice, taking mealtime insulin can become a normal part of your routine.

How is mealtime insulin dosing determined?

There are a number of factors that determine your overall insulin needs. For example, the daily insulin dosage for someone with type 2 diabetes whose body still produces some insulin will probably be less than someone with type 1 diabetes whose body makes no insulin. 

Other things that play a role include:

  • Your weight
  • Your activity level
  • Your overall health
  • Your stress level
  • How long you’ve had diabetes
  • When and how many carbohydrates you eat each day
  • Other medications you are taking

Based on this, your doctor will provide you with a plan for incorporating mealtime insulin. Your post-meal blood sugar is primarily related to the amount of carbohydrates you’ve taken in, so you’ll be advised on how to match your carbohydrate intake to your mealtime insulin dose. In some cases, your doctor may start you off with a set dose of insulin to take before you eat and suggest you consume a certain amount of carbohydrates at each meal.

The insulin to carbohydrate ratio

In other cases, you may be taught about an insulin to carbohydrate ratio, which indicates how many grams of carbohydrates are covered by one unit of insulin. This allows you to change the amount of mealtime insulin you take based on what you eat. To calculate your mealtime insulin, you need to take the number of carbohydrate grams in your meal and divide it by the grams of carbohydrates covered by one unit of insulin.

To illustrate, assume your insulin to carbohydrate ratio is 1:10, which means one unit of insulin covers 10 grams of carbs. Then assume you plan to eat 50 grams of carbohydrates:

50/10 = 5

You would take 5 units of insulin before your meal. 

Correction doses of insulin

Sometimes, your blood sugar is already higher than usual, so you need to add more mealtime insulin in addition to the proportionate dose for your meal. This dose, called a correction dose, helps get you back to stable blood sugar levels. Your doctor will give you what’s known as a correction factor. This is the amount your blood sugar is expected to decrease per each unit of insulin given. To determine a correction dose, you subtract your target blood sugar from your current blood sugar and divide it by your correction factor.

As an example, say your blood sugar is 220, your target blood sugar is 120, and your correction factor is 50.

220-120 = 100

100/50 = 2

You would take 2 units of insulin as a correction. This would be added to any additional insulin needed to account for the carbohydrates in your meal.

How do I know if I’m taking my mealtime insulin correctly?

It can feel a bit overwhelming in the beginning, so don’t hesitate to reach out to any members of your diabetes care team. Your doctor, dietitian, or diabetes educator will work with you to make sure you know how to properly count carbohydrates and correctly calculate your insulin dose. You should be provided with written details of your diabetes treatment regimen. There are apps and insulin dosage calculators online, as well as tools to help you count your carbs, but always check with your doctor before using to ensure their accuracy.

The bottom line

It’s important to remember mealtime insulin dosing needs to be closely monitored. You and your doctor will work together to track your blood sugar and see if any adjustments need to be made to your insulin regimen. If you notice your blood sugar seems high at night, or you start a new exercise program and your blood sugars start trending lower, these are important things to let your doctor know. Together, you can finetune your mealtime insulin to keep your blood sugar in a good range.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Sep 25
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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