Could your insulin pen (or whatever you use to administer it) have been faulty?
I had DKA a few years ago when the pen I used malfunctioned. It was one of the type that had an insulin-filled cartridge inserted into it, and apparently it turned out that the glass had cracked and the insulin leaked out into the pen, instead of through the needle into me. It looked and felt as though it was working properly, but obviously wasn't, though the fault wasn't picked up until I was in hospital and resumed doing my own injections. I'd been fine while I was on the drip, then everything went haywire when I started using my own pen again, and when that was checked, it turned out to be faulty.
I now use the pre-loaded pens and haven't had that problem again. I also check they're working now, which I should have done before, of course, but didn't.