It’s too bad they didn’t catch it sooner! I’m sorry you had to go through that.
Metformin isn’t intended to replace insulin in people with T1. It can just help with insulin sensitivity. As a T1 without any functioning beta cells (as far as I can tell), I’ll always need insulin.
So this is what happens to me when I forget a dose of metformin. Today was one of those days where I could NOT figure out why the heck I was running SO ridiculously high for most of the day. It finally came down when I came home from work (a time I typically go low). Then as I went to take my evening medications, I saw that I hadn’t taken my morning medications, which includes a dose of metformin.
I don’t remember noticing a huge, dramatic shift in my insulin doses when I first started taking metformin about two years ago. But clearly, over the past couple of years I’ve adapted my insulin doses to it, or else it’s begun having a greater effect on me, because this type of disaster happens every time I forget a dose.
I had my endo appointment today, and it was probably the most helpful appointment I’ve had so far with this doctor. I’ve been seeing him for 1.5 years, and I think the longevity is helping a bit with our interactions.
He suggested I switch to Lantus for trips after I discussed my problems with Tresiba and travelling.
I’ve also gained a couple more pounds. It may just be water-weight, but I thought I was losing so I still find it concerning. He asked a lot about hypoglycemia, and he proposed that I might be struggling with weight due to the inflexibility of Tresiba. I told him about how exercise and my monthly cycle can result in my combating lows while I wait for my Tresiba dose change to catch up. Combatting lows means eating more than I would normally. These lows are hardly visible on my clarity reports because I usually head them off before they occur or address them quickly at night.
When I suggested a full transition to Lantus he was very open to it. I think it was helpful for me to pose all the problems and lead him to the solution I wanted 
He’d come to the same conclusion by the time I was done describing everything.
Carbing up a bit after a workout can make a huge difference in how much extra I need to eat over the next day or two. I’ve been trying to make it more of a priority to have carbs right after a workout. It can mean the difference between waking up 3-4 times during the night and eating tons of carbs (100+ total on an occasion when I forgot to carb up at all) to avoid a low or just having 30 after a workout. I think Eric wrote about how liver and muscle glycogen can get used during heavy workouts, and the carbs you eat immediately after a workout are more effective at replenishing your stores (instead of eating tons of carbs later on and slowly replenishing stores). I’m not going to pretend to completely understand all of the factors there, and I’m sure he said it better somewhere else (so search for it!).
Anyway, all that is to say that the effect seems even more pronounced while on Metformin, and it may be because I usually take Metformin in the evening around 2 hours after my workout. So carbing up immediately after my workout and before my Metformin dose seems to work best at allowing me to maintain the same basal dose (which is the goal with Tresiba). It’s not perfect of course, and all of this seems to be much more challenging in 2 weeks of my cycle (the week before my period and during most of my period). The two weeks immediately after my period often seem dreamy in comparison.
I’m hoping that with Lantus I won’t need to carb up quite as much because I can easily reduce my dose on the days I work out. My doctor seemed to think switching to Lantus would really help stabilize my weight, and I think that makes sense. We’ll see if it actually has any impact though.
Anyway, my monthly cycle basal needs seem to be pretty much the same now @T1Allison. I’m pretty sure the basal need changes I mentioned earlier were entirely related to exercise. It’s just that the effects after exercise lasted longer if I didn’t carb up properly, so it obscured the problem. I hypothesize that replenishing the glycogen stores on metformin is more challenging, so the effects last longer (just a theory… I don’t know if that’s true). So any variation in exercise can create the appearance of a more dramatic variation in basal needs. If that makes sense?
I’m excited to start Lantus again. I’m really looking forward to being able to change my dose easily. Sorry for all the rambling! I’ll be impressed if anyone actually reads all that 
I only started metformin on top of my insulin 4 days ago and the results are unbelievable. Honestly, I don’t really believe it.
Here is my nightscout average for the last 3 months. 6.1% A1c estimate. I thought I was doing great.
Rish
Man that is tempting me to crack open my bottle.
Are you taking standard met or the extended release? And once or twice / day?
That is really amazing results. Thanks for posting. I look forward to more of your informative posts. Wow!
500mg XR once a day after lunch. My endo suggested upping the dose by 500 every week or two until I hit 2g (subject to side effects such as diarrhoea etc) - but I’ll see how it goes with just the 500.
Do you have any residual insulin production? The LADA label on your profile would suggest that might be the case. If so, I’m thinking that the metformin would help a lot to amplify the effect of the residual insulin as much as possible.
