In this section
Flexible bolusing, sometimes called flexible bolusing
or multiple daily injections (MDI), is designed to mimic the body’s normal
production of insulin. It requires you to inject a background amount of insulin
daily and an extra dose of rapid acting insulin (known as an insulin bolus) with each meal. This means people
on MDI will have a minimum of 4 injections each day.
Basal insulin (e.g. glargine or Levemir®) is background insulin that helps to keep blood glucose levels
(BGLs) in target when food isn’t being eaten.
Bolus insulin (e.g. NovoRapid®
or Humalog®) is rapid acting insulin given before each meal that allows you to
use the carbohydrate you eat for energy. This dose should be matched to the
amount of carbohydrate you eat.
“Flexible” means you can
inject different amounts of insulin depending on:
Adjusting your insulin doses to match your food intake,
and correct any BGLs that are above target, will help you keep your BGLs in
target more often.
It also means you can be flexible with the timing
of your meals. Unlike twice-daily insulin regimens, if you are using flexible bolusing
your meals do not have to be eaten at strictly the same time each day/night.
Flexible bolusing can also help you manage sport,
illness and stress more easily.
For success with flexible bolusing it is important to
have a good understanding of carbohydrate counting. See your dietitian
if you need help with carb counting.
The Insulin to Carbohydrate Ratio (ICR) is the number
of grams of carbohydrates that is covered by 1 unit of insulin. For people who
prefer to count carbs in serves (instead of grams) the carb ratio can also be
written as units of insulin per serve of carbohydrate.
Carb ratios vary amongst people and can be affected by
the time of the day, and other factors like changes in weight, age, or
Below is an example of two different ICR’s applied to
the same food.
To calculate the ICR the 500 rule is sometimes used.
You take the number 500 and divide it by the current total daily dose (TDD) of
insulin. For example, if you usually have 20 units of glargine and 10 units of
NovoRapid® with each of your three meals then your TDD is 50.
Often children under 5 years of age need to use the
300 rule for more accuracy. The 300 rule may also be helpful for older children
and teenagers, especially if their TDD is low (e.g. less than 1 unit of insulin
per kilogram of body weight).
To check if your ICR is correct you need to check your
BGL 2-3 hours after eating. If the BGL is more than 3mmol higher than what it
was before the meal, you need to consider making your carb ratio stronger.
A correction factor is sometimes called the Insulin
Sensitivity Factor (ISF). This is a measure of how powerful one unit of insulin
is in your body. The correction factor is used to work out how much extra
insulin you need to give when your BGL is above target.
For example, a correction factor of 2 means that 1
unit of insulin should lower your BGL by 2mmol/L. So if your BGL is 9mmol/L and
you give 1 unit of insulin, your BGL should come down to about 7mmol/L in the
next 2-3 hours.
To work out what your correction factor is, take the
number 100 and divide it by your TDD. Like the previous example, if your TDD is
50 units, your correction factor is 2.
To check if your correction factor is right, check
your BGL logbook. Look at times when you have added a correction dose of
insulin to your meal dose, and see what the BGL was 2-3 hours later. If the BGL
is not coming back to target (i.e. you are having high or low BGLs 2-3 hours
after that meal) then you know your correction factor might need to change.
When you are using flexible bolusing your pre meal insulin
dose will change all the time. To help work out the dose you can use tools like dosing cards (see below example), or a meter or app with a bolus calculator feature built in (one bolus calculator linked at end of this page).
There are several glucose meters and phone apps available
which allow you to program different ICRs and ISFs at different times of the
day to help you calculate your insulin dose.
Remember that ICRs and ISFs will change over time,
especially in children and young people who are still growing. This is why its
important to regularly review your settings in whichever tool you are using.
NOTE - the pre meal target blood glucose level is 4 –
Snacks are not compulsory on MDI. If you want to snack
in between your meals then aim to keep it less than 15 grams of carbohydrate, unless
you are planning to give extra rapid acting insulin.
If you are consistently feeling hungry in between your
meals then consider increasing the size of your main meal or including more low
GI carbohydrates such as wholegrain breads, grains, dairy foods, legumes,
vegetables and some fruits to improve your feeling of fullness.
RCH Diabetes Team: Monday-Friday 8am-4pm (03) 9345 6661 or firstname.lastname@example.org
RCH acknowledges the Children’s Diabetes Centre, at
Perth Children's Hospital, WA for their permission to adapt their resource
“Guide to Flexible Insulin Therapy for Families”
This is an online bolus calculator to use if you have had education. This calculator is different to using a dosing card or app on the phone.
To use this calculator you need to know what your carbohydrate ratio is and your insulin sensitivity is.
Flexible bolus calculator