Insulin Basics
The ultimate goal of insulin therapy is to mimic normal insulin levels. Unfortunately, current insulin replacement therapy can only approximate normal insulin levels. Insulin therapy for type 1 diabetes requires multiple injections or using an insulin pump (continuous subcutaneous insulin infusion – CSII). The more frequent the insulin injections, the better the approximation of natural or normal insulin levels. Discuss with your medical provider the insulin regimen that is best for you.
On this page you will learn about:
Normal or Non-diabetic blood sugar levels and insulin release from the pancreas
Natural insulin (i.e. insulin released from your pancreas) keeps your blood sugar in a very narrow range. Overnight and between meals, the normal, non-diabetic blood sugar ranges between 60-100mg/dl and 140 mg/dl or less after meals and snacks.
See the picture below of blood sugar levels throughout the day in someone who does not have diabetes.
To keep the blood glucose in a narrow range throughout the day, there is a low steady secretion of insulin overnight, fasting and between meals with spikes of insulin at mealtimes. Adapted: Jacobs DM Care 20:1279, 1997
To keep the blood sugar controlled overnight, fasting and between meals, your body releases a low, background level of insulin. When you eat, there is a large burst of insulin. This surge of insulin is needed to dispose of all the carbohydrate or sugar that is getting absorbed from your meal. All of this happens automatically!
More About Natural Insulin Release
Insulin is continuously released from the pancreas into the blood stream. Although the insulin is quickly destroyed (5-6 minutes) the effect on cells may last 1-1/2 hours. When your body needs more insulin, the blood levels quickly rise, and, the converse – when you need less, the blood levels rapidly fall —The situation is different when you have diabetes and are getting insulin replacement therapy. Once you have injected a dose of insulin, it is going to get absorbed into your bloodstream whether you need it or not.
At mealtime, a little insulin is released even as you are first smelling or chewing the food. This gets your body ready to receive the sugar load from the meal. Then as you eat and the food is digested, the sugar levels rise which causes a surge of insulin. The insulin levels rapidly climb and peak in about 45 minutes to 1 hour before falling back to the background or basal levels – The situation is different when you have diabetes and are getting insulin replacement therapy. You have to calculate how much carbohydrate you are going to eat and how much insulin you will need. And you have to try to mimic natural mealtime insulin release with injected insulin.
See the picture below illustrating overnight, fasting and between meals insulin, and the large spikes of insulin that accompany meals.
To keep the blood glucose in a narrow range overnight, fasting and between meals, there is a low basal/background secretion of insulin. Adapted: Jacobs DM Care 20:1279, 1997
To control the blood glucose while eating, there is a rapid burst of insulin at mealtimes. These mealtime surges of insulin peak within about 45 minutes and then fall back to the basal/background levels. Adapted: Jacobs DM Care 20:1279, 1997
Principles of insulin replacement
When you have type 1 diabetes, you will need to start insulin therapy because you no longer make your own insulin.
The insulin therapy tries to mimic natural or non-diabetic insulin secretion. There are two components of insulin therapy.
1. Background or basal insulin replacement
Intensive insulin therapy tries to duplicate the body’s natural pattern of insulin secretion. With intensive insulin therapy you need a low steady amount of insulin overnight, while fasting and between meals as illustrated by the dashed line. Adapted: Jacobs DM Care 20:1279, 1997
- Controls glucose overnight and between meals by keeping fat in fat tissue and curbing glucose production from the liver.
- Provides a low, continuous level of insulin.
- Can be a long-acting insulin, which you inject once or twice daily such as the insulin analogs, insulin glargine, insulin detemir and NPH.
- Or can be a rapid-acting insulin continuously infused under the skin, if you are using an insulin pump.
- Represents about half of the body's daily insulin requirements.
2. Bolus insulin replacement
Intensive insulin therapy tries to duplicate the body’s natural pattern of insulin secretion. With intensive insulin therapy you need a rapid surge of insulin at mealtimes as illustrated by the golden lines. Adapted: Jacobs DM Care 20:1279, 1997
There are two kinds of bolus replacement:
Mealtime Bolus – to cover the carbohydrate in the meal or snack.
High Blood Sugar Correction Bolus – provides extra insulin to return the blood sugar back to the target level when your blood sugar is too high.
- Bolus Insulin is usually provided by a rapid-acting insulin analogs, such as insulin aspart, insulin lispro, and insulin glulisine or Regular insulin.
- Represents about 10% to 20% of the daily insulin requirement at each meal, or about 50% of the body's daily insulin needs.
Read about the different types and characteristics of insulin that are suitable for basal and bolus insulin.
Learn more about :
- Types and characteristic of insulin medications
- Insulin administration
- Designing an insulin regimen
- Calculating your insulin dose
- Intensive insulin therapy
- Insulin pump therapy
Intensive insulin therapy tries to duplicate the body’s natural pattern of insulin secretion. With intensive insulin therapy you need a low steady level of insulin overnight, fasting , and between meals, and a rapid surge of insulin at mealtime. Adapted: Jacobs DM Care 20:1279, 1997