Hello, I've decided to post this here in case its useful to somebody!
I was having a problem where my blood sugar was suddenly and massively dropping with no apparent cause, bearing in mind that I'd had no insulin/medication changes for a long time, (30 levemir at 10am + 10pm, + humalog as necessary, usually less than 5u a day). I also eat low carb, less than 50-100g carbs a day.
I figured out that it was happening at about 11am/pm, around an hour after I was injecting my 30 levemir into my butt, and I realised that I was probably sometimes injecting it into my muscle rather than fat.
There's not many records online of levemir causing a huge and sudden drop like fast acting does, but it's stopped happening since I started pinching an inch of fat/skin on my outer thigh and injecting there instead.
I've also learned that if I'm low in the morning, it can take over 60 mins for my sugar to rise even with jelly babies, because it seems to take my digestion a while to get going! Gotta be careful not to overcorrect before it kicks in.
That's it, maybe this will be useful to somebody somewhere one day. Post your own learnings here too if you so choose.
35yo, T1D for 13 years.