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Dosing Insulin

One of the things patients often fear about being diagnosed with diabetes is insulin injections.

In most cases, if you have type 1 you will be taking insulin a number of times a day.   And, most likely because you are new to diabetes, the decision about which insulin to take and how to take it will be made by your health care provider.

But as you learn more about the disease and improve your self-management skills, you will be able to participate more fully in your care.

If you have type 2 and are transitioning to insuli—or transitioning from taking one injection of basal insulin a day to a regimen that has you injecting insulin before each meal and a dose either at bed or in the morning—it can be anxiety provoking.  It is a stark indication that your pancreas is no longer providing sufficient insulin.

Whether you have type 1 or type 2, if you need to take multiple injections of insulin a day, understanding the different ways insulin is titrated can be empowering—and having a discussion with your health care provider about which way may suit your circumstances the best, can diminish apprehension and give you a measure of control.

There are three basic regimens available for people who use a basal/bolus approach.

Fixed Dose

With this method, a set amount of insulin is given at each meal, and the amount per meal can be the same or different.

For example, someone may take 6 units at breakfast, 4 at lunch and 8 at dinner, or 8 for all meals.  The advantage of this method is primarily ease-of-use.  The amount is the same regardless of your blood glucose readings or what you eat.

The downside is its rigidity.  If your blood sugar is very high before a meal, it is unlikely that the insulin given will be adequate to bring your glucose down to target levels after the meal.  The same is true for food consumption; the insulin will not be adequate to cover a significant amount of carbohydrate above your usual portion.

The Fixed Dose method is predicated on the assumption that people will be eating a consistent amount of carbohydrate meal-to-meal.  For people on fixed schedules, those who tend to eat the same type and quantity of food on a regular basis, this type of dosing works well.  It is also appropriate for people whose understanding is limited, or who are new to insulin and want to ease into more sophisticated approaches.

However, if your food (especially carbohydrate intake) varies  widely, your blood glucose may well follow, and you will end up with a pattern of erratic readings.

Sliding Scale

A sliding scale varies the dose of insulin based on blood glucose level.  The higher your blood glucose the more insulin you take.

The Sliding Scale method is more precise than fixed dose insulin in that it takes account of the fact that people’s blood glucose is not always in the normal range before meals.  Sliding Scale requires a bit more "patient investment" than Fixed Dose, as you might imagine.

Whereas in a fixed-dose scheme, while strongly recommended it is not absolutely necessary to take a blood glucose reading before giving an injection.  In order to know how much insulin to take via a sliding scale, you have to check.  Like the fixed dose the sliding scale approach assumes that a consistent amount of carbohydrate is eaten at meals.

This method works well for people who want more control over their blood glucose, are willing to do the requisite monitoring, and are committed to a structured meal plan.

Carb Counting with Fixed Dose and Sliding Scale

Both fixed dose and sliding scale assume that you will count carbohydrates in one of two ways.

  1. Basic carb counting, in which, a set amount of carbohydrate is assigned in grams or portions and patients choose different carbohydrate servings to equal the target amount
  2. The plate method, which is a visual approach to carb counting where between ¼ and 1/3 of the meal plate is reserved for carbohydrate containing foods. 

In both methods the foods can vary but the total carbohydrate remains the same.

Matching Insulin to Carbohydrate

In this approach, insulin dose is based on two factors: the amount of carbohydrate eaten and the difference between actual blood glucose and target blood glucose. 

Patients work with two ratios: an insulin to carbohydrate and a correction factor, along with a blood glucose target.  The insulin to carbohydrate ratio indicates how many carbohydrates one unit of insulin will provide coverage for and the correction factor describes the glucose lowering power of one unit of insulin. 

If an individual had a insulin to carb ratio of 10 and a correction factor of 50, it would mean:

  • She would take one unit of insulin for every 10 grams of carbohydrate eaten

  • One unit of insulin would lower her blood glucose 50 points.  

This method is more physiological and more flexible than Fixed Dose or Sliding Scale, because it allows for differences both in glucose levels and carbohydrate intake. 

To use this method you must have adequate arithmetic skills and be willing to count carbohydrate grams or servings. But Insulin to Carb Matching is often worth the extra work because it allows for much more flexibility in food choices while enabling you to become more actively involved in your care. 

Updated: July 7, 2011

Page last updated: April 21, 2014