I got my first Moderna shot 1 1/2 weeks ago. Don’t plan on too much sleep for 12-20 hours after shot. I got my shot at lunchtime and my BG tanked in the evening until about 1AM without taking any afternoon/evening insulin. Then, like a switch was flipped my BG shot up about 150 points. Then it took another 12 hours and more fast acting insulin than I would normally use over a 4 day period to come back to normal. After fighting to get BG down for about 12 hours, it just dropped like a rock back to normal in about 45 minutes.
Also ran a little fever during that time which came and went in parallel with BG fluctuations. It is rare that I stray outside of 55-120 range, so this was pretty scary.