# Re: [IP] U-500 Insulin

```Dick Hunt wrote:
> <<Hi Mark,
>
>  > how does [using U-500 insulin] relate
>  > to a 15:1 carb ratio?  Does that mean
>  > it is now 15:.2?
>
> Yep. Of course, it is more easily expressed as 75:1 (75 grams of
> carbs to 1 "five-fold unit" of insulin).>>
>
> In relation to Felix's comments, if you are at a ratio of 15:1 and will go
> to about 75:1, how will you manage that?  As an example, at mealtimes with a
> carb intake of say 60 carbs, even 1 unit of insulin would be a challenge to
> bolus.  Also, a snack of say 15-20 carbs would be almost impossible.
> I believe my math is correct, or please correct me, if I'm wrong - the U-500
> is 5 times more potent, right.
>
> Dick
>

I'm going to chime in on the U-500 discussion here and add to Felix's
and Dick's comments.  The U-500 insulin is 5 times stronger than u-100.
Most people I've seen considering U-500 are taking well over 200 units
daily and some closer to 500.   Most of the time their insulin to carb
ratios are not anywhere near 1 unit for 15 grams of carb it's more like
1 or 2 units  for every 1-3 grams of carb.   I was kind of assuming that
the example from the original poster was just for discussion purposes
and not their actual insulin to carb ratio.   If they really are only
taking 1 unit for 15 grams of carb I'd say some serious post prandial
testing is due to reassess the ratio.   If the U-100 carb ratio is 1:3
then you program 1:15  for the U-500 in the pump wizard  and it makes
dosing snacks feasible.

Usually in these cases also the correction factor is also very high ie 1
unit lowers sugar  5 to 10 points not 50.    When setting the correction
factor in the pump for u-500 remember this is one you multiply not
divide.  For example a U-100 sensitivity or correction factor of 1 unit
lowers blood sugar 10 points is now 1:50 with U-500.

The patients I've seen thinking about switching blood sugars are not in
control even with the massive quantities of insulin they're taking.
It's not unusual to see blood sugars consistently 300 to 500 and
therefore also requiring large doses of insulin for corrections.

In my opinion using U-100 in a pump becomes difficult is when TDD is
over 200 units daily.   First of all if you have to bolus large doses of
insulin at meals most people would end up having to bolus two or three
times to get the dose in because of the preset max bolus limits set on
the pump.  I can't remember the limits on other pumps but Minimed's is
25 units.  If someone needed to bolus 45 units they can't.  So they'd
have to split it, wait the umpteen million minutes it takes the pump to
deliver the first 25 units and then remember to program the rest.  You
could never really effectively use square wave or dual wave when you
exceed the pump limits and again would require multiple boluses.  That's
a major drawback.

Regarding reservoir changes again that depends on the TDD.  It's one
thing to change a reservoir every one or two days but it would be a lot
more difficult if you typically used over 300 units a day.

Also at these kind of TDD the volume of the insulin itself can make a
major difference.  I've seen equivalent dosing with u-500 ( ie no
increase in total insulin or ratio's per se) lower the average blood
sugar by 200 points.  If the only thing that changed was the
concentration of the insulin then you're getting back to principle that
smaller depot means better absorption.

I used U-500 insulin for a few months back when they only had the 500
series of Paradigms and I was on prednisone.    My TDD is usually
anywhere between 60 and 80 units daily but can be 150+ when I can't
breathe and am on steroids.  It was really helpful then.   I kept on it
for a few months afterwards and that ended up being problematic as my
settings were sometimes a little too high or too low and the
concentration made it more difficult to fine tune the settings.  It was
convenient though to only have to change every 3 days instead of every
one and half to two.   Now I love having the 300 unit reservoir and I
use Apidra.  However if I ever needed more than 200 units daily I'd
switch back to the u-500 in a heart beat.

Having personally used it I agree that it would be nice if the pumps
allowed calculations for u-500 dosing.  I don't know if they can since
the u-500 isn't FDA approved for pumps.

I also think that there's a need for the newer analogs to come in the
U-500 concentration if it's possible to manufacture them that way.

Gosh this is getting long so will stop.

Diana
.
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