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Understanding PDM and Pod Function 12
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12 Understanding PDM and Pod Function
Insulin on board (IOB)
Aer a bolus is delivered, the amount of insulin that is active in the body decreases
over several hours. e Bolus Calculator approximates this decrease in insulin by
calculating an ‘insulin on board’ (IOB) value. e calculated IOB value decreases
over time and reaches zero at the time set by the Duration of Insulin Action value.
For example, if your Duration of Insulin Action is 4 hours and an 8 unit bolus is
given at 6 pm, the IOB amount decreases steadily over time as shown in this graph.
Types of IOB: meal IOB, correction IOB, or both
A bolus, and the IOB from that bolus, can be entirely meal, entirely correction, or
both. e following graphs show how the IOB from a 4 U total bolus decreases
over time with a Duration of Insulin Action of 4 hours.
Entirely meal
A meal bolus is calculated when you are
eating a meal and your blood glucose is less
than your Correct Above value. e IOB
from this bolus is entirely meal IOB.
Entirely correction
A correction bolus is calculated when you
are not eating and your blood glucose is
above your Correct Above value. e IOB
from this bolus is entirely correction IOB.
Both meal and correction
When you are eating and your blood glucose
is above your Correct Above value, the total
bolus includes a meal bolus and a correction
bolus component. Likewise, the IOB from
this bolus has a meal IOB and a correction
IOB component.
11 pm10 pm
9 pm
8 pm
7 pm6 pm5 pm
Take 8 U bolus at 6 pm
Duration of Insulin Action set to 4 hrs
4 hrs after the bolus,
IOB has returned to zero
3 hrs after the bolus: IOB = 2 U
2 hrs after the bolus: IOB = 4 U
1 hr after the bolus: IOB = 6 U
0
2 U
4 U
6 U
8 U
IOB (U)
10 pm
8 pm
6 pm
0
2 U
4 U
Meal IOB
IOB (U)
10 pm
8 pm
6 pm
0
2 U
4 U
Correction IOB
IOB (U)
10 pm
8 pm
6 pm
0
2 U
4 U
Correction IOB
Meal IOB
IOB (U)