Just a reminder that Control-IQ 's behavior is pretty much entirely controlled by your settings. There are absolutely valid criticisms of the system (“I don’t like the 110 target”, “I don’t like the locked 5 hour DIA”, “It only gives 60% of a correction”, “it doesn’t give corrections often enough”, etc…), but if you feel like it’s ineffective at doing what it’s programmed to do, then that comes down to settings.
Correction factor is the aggressiveness control, and it works on both ends of the spectrum. It controls how much power the pump has to alter both highs and lows. If your CF is set to too high of a number, i.e. less aggressive, then the system is less capable of withholding insulin when a low is predicted. It thinks that it only needs to withhold a smaller amount than is actually true. Too high of a number here incapacitates the system, so it can’t effectively prevent lows. Too low of a CF number of i.e. over-aggressive, can also cause lows by over-correcting highs. You would recognize that pattern by really fast changes, such as highs plummeting into lows, which then rebound into highs again. You’re really looking for that sweet spot in the middle.
There’s no guarantee that CF is the problem, though. A basal rate that is set too high can hide insulin on board from both you and Control-IQ. It can’t properly foresee how much power IOB has to drop your BG in this case, so doesn’t know to suspend. If there is no insulin on board and the system has reduced your basal, then it expects your BG to turn around at any moment, but it doesn’t have correct information to know better. That’s why basal testing is so important. Good basal rates are the foundation of Control-IQ (and the DIY algorithms, too), and then Correction Factor just sorta amps the algorithm up and down.
If you find you have lots of IOB on board when the lows happen, then I:carb setting may be the culprit, or it may just come down to bolus timing.
If you’re having so much trouble with lows and it’s a recent development, if could be that you’ve made changes that make you more sensitive to insulin in general. More active during the summer, dietary changes, weight loss, medication changes, etc… In that case, all 3 settings might need changed!
Control-IQ is the most powerful commercial system, but it’s only as good as it’s settings. I really think it’s best suited for patients who understand how the settings work and/or those who have a medical support team who understands how the settings work, and can make appropriate adjustments. Tandem is working on software that can recommend adjustments, but until that’s released, this nature of the system may be a downside for some. Unfortunately, not all doctors are good with the evolving tech, so there’s definitely an argument for Medtronic and O5 in these cases.