My dad is an elderly diabetic and didn't take care of it and due to that he has developed a neurogenic bladder:
Neurogenic bladder is the name given to a number of urinary conditions in people who lack bladder control due to a brain, spinal cord or nerve problem. This nerve damage can be the result of diseases such as multiple sclerosis (MS), Parkinson's disease or diabetes.
Dad did the same thing - he says he feels "more comfortable" at a high blood sugar rate like 180-200 which is way too high, but that's what he's become accustomed to living with after eating way too many carbs for years and his insulin mechanism just wore out.
Early in his diabetic diagnosis he was "sciencing the shit" out of it experimentally, figuring exactly what he could eat and trying to "scrimp" on insulin (back when it was really high, it's capped at $35/month now I believe) He was taking his insulin either not often enough, or we'd catch him not taking it and he'd inject it saying 'I'm gonna have to keep eating all night so my sugar doesn't crash" well...that's why you take the long-acting insulin in the morning instead of at 4pm when we go "oh my god your sugar is 250". And he basically became lax about it living on his own as his health declined.
So basically due to inattention (some of this is stubborn, some of this is just memory issues as he's had strokes) dad cannot control the signal to urinate and his bladder will fill up and he's pretty much permanently catheterized. If you can use that as encouragement/warning for your loved one to mind their blood sugar and take care of themself to avoid other more annoying complications, please do!
(Dad is actually now in assisted living so they are monitoring his sugar and making sure he takes his meds correctly - that's another "If you don't take care of yourself someone else will have to help" caution.)
The other posters' suggestions about a wearable blood sugar monitor that will beep or alert on his phone if he's high is an awesome idea. Dad could have used this because we'd ask him what his last sugar level was and he'd be like "oh, the monitor's battery is dead" (it wasn't) "Oh, my lancet pen is broken/I don't have lancets for it" (We'd invariably find another pen and an entire box of lances that he overlooked.)
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