Did I read somewhere that the new Omnipod system calculates insulin on board differently than the old system? Ever since switching to the new system my blood sugars have been higher than usual, and I notice the system often won't bolus for my bg reading (when the previous system would). I'm wondering if it's a setting in the new system or just how the new system works.
The main change they made was to include meal IOB in the IOB calculations, like all the other pumps do. The old system assumed that a meal bolus was completely covered by the carbs you bolused for, so would not keep track of meal IOB. Many people complained about this so they changed it . It is explained in the manual, on pages 143-146, with several examples.
Personally, I preferred the old system of calculation, even though the new method is supposedly "safer".
Yes, in some cases now, it will not deliver a correction based on BG if there is enough meal IOB remaining on board.
There's also been talk here about the length of time setting for the insulin that's used. The PDM calls this "insulin action". Many here have found that setting it to 2.0 hours helps with the IOB calculation more on the new PDM. For me, I originally had it set to 4.0 hours on the old PDM. I've found better control by the 2.0 hours on the new PDM. YMMV so talk to your doc or diabetes educator about it first.
If you bolus a *second* meal before the first meal has been completely adsorbed by your body and if you enter your BG with the second bolus you will not get adequate insulin.
Check your 'insulin action time'; settings, system setup, bolus/basal/calcs, ratios/factors/targets, insulin action. If this time is routinely *much* longer than your time between meals (including snacks; anything that requires a bolus) you need to do sometime special with the new PDM to avoid under bolusing. The bug is that the new PDM erroneously uses what remains of your previous meal bolus against the carbs you are consuming even if it isn't long enough for the previous meal to have been adsorbed.
This is the only actual bug that I'm aware of. It can be avoided, for example by not entering the BG with the second bolus. It can be detected by examining the final confirmation screen (the one with the 'extend' option) - if you have "Meal IOB" when you are delivering a meal bolus then you need to consider whether there has been sufficient time since your previous meal for it all to be absorbed. If not you can *add* the amount of it that remains to be absorbed to the carb count you're about to eat to get the right result.
Apart from this the change *does* help with correction boluses. The PDM now takes into account the bolus for the meal. Consequently if (and ONLY if) all the numbers are set up correctly in the PDM the PDM won't deliver a correction bolus for the after-meal highs that occur with high carb meals.
You may find that the new PDM under-corrects after a meal as a result. What this probably means (assuming you are not encountering the closely-spaced-meals bug) is that your insulin action time is too long - the PDM is assuming insulin is in your blood stream when it's actually all long gone. You *might* also have too low a correction ratio, but that seems unlikely.
Some of us have found that while the old PDM seemed to work ok with a 4 hour insulin action time (with Humalog), the new one actually works and works better with a 2 hour insulin action time. It's important to review your correction ratio and insulin/carbohydrate ratios before messing with the action time. If they're wrong then it will be very difficult to establish the correct action time.
John Bowler