# [IP] Strength and Volume

```A lot of people seem to be confusing insulin strength with insulin volume in
trying to figure out how much to prime the Silhouette.

Insulin comes, or used to come, in the following strengths: U-20, U-40,
U-50,  U-80, U-100, and U-500. One unit of insulin has the same effect no
matter what its strength is. The volume occupied by one unit of insulin
varies according to the strength of the insulin:
One unit of U-20 occupies 1/20=0.050 milliliter (ml) of volume.
One unit of U-500 occupies 1/500=0.002 ml.
One unit of U-100 occupies 1/100=0.010 ml.
One unit of U-50 occupies 1/50=0.020 ml.

In priming the Sil, the objective is to fill the space (volume). MiniMed
measured that space and found that 0.7 unit of U-100 would fill that space
(0.007 ml). For U-50, 0.35 unit (0.007 ml) will fill that space.

Those who try to use a unit of U-100 as though it were a measure of volume
are in for trouble as soon as they try to extend their reasoning to cover
other strengths of insulin. Not all insulin today is U-100. The implanted
pumps of the future will probably use U-500.

Tom Beatson
dx 12/9/42, 506 1995, 508 2000
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