Hi, Kiryn, welcome to the club, even though it's a club which you didn't really want to join!
Honeymoon period ending may well be a reason for increasing lantus requirements.
Your 16.5 really doesn't sound crazy high. We can't give dosage advice on here, because we're not doctors (some of us are, but they can't either), but the lantus maker's advice to doctors suggests 0.2 units for each kg body weight as a rough starting point and then adjust from there depending on results.
https://www.lantus.com/hcp/dosing-titration/dosing-calculator
I'm 78 kilos which suggests 15.6, but basal testing shows I'm ok with 14, so not far out.
Learn about basal testing, it makes a big difference. Lantus should hold your bg levels steady for extended periods in the absence of factors which tend to increase or decrease levels such as food, exercise and insulin.
What that means in practice is waiting until your last bolus fast acting shot has worn out, typically 5 hours, and your last meal has been digested, again, around 5 hours (but if there was fat in it, can take way longer - google pizza effect), then just sit around for eight hours or so watching telly, or have a long lie in at the weekend, test every hour or two, and levels should hover around the same mark. At the end of the eight hours, if it's gone substantially up or down, that's an indicator that the dosage might need tweaking.
This can be done with bg meter testing, but is a lot easier with cgm. The aim is to try to get a nice flat line like this:
Maybe a bad example to use, as the green line shows the tail end of my last fact acting still playing a part till 3am, but not much, and even so, still trotting along quite level from 4am to 9am.
Your pancreas is far from dead. It's still doing a lot of stuff. Your alpha cells will still be sending out glucagon as a message to your liver to release glycogen (stored glucose) if you drop too low, which is why if you have a bad hypo while sleeping, it's extremely unlikely you will die: the insulin will wear out, the glucose released by the liver will raise you.
It's only really the beta cells in the exotically named Islets of Langerhans in the pancreas which have died.
Good luck, Kiryn, T1 isn't a walk in the park, but you've been doing this long enough already to know that with a bit of forethought and planning, anything is possible!
