I posted this already under the 'introducing' post you did in response:
hi Mammamoo..... it was probably a hypo you had. It's important to get into the habit of testing your BGLs... even when half asleep. I do this myself, sometimes I may actually sleep through a hypo though and I know about it as I get the liver dump happen and I usually can feel I've had a hypo too. Having a hypo at night is weird I know... it gives you that horrible spinning out/wave feeling and sometimes you're wondering if it's sleepiness or what.... but usually when I feel that way and test I'm too low. We are supposed to avoid getting hypos as they can be dangerous if left untreated. Keep your glucometer and a quick acting carb near your bed. My endo advised me to eat a quick acting carb first and then if you are not near a meal within the next 15 minutes, you then need to eat a low acting carb to keep you BGLs stable until your next meal. Yes, that sometimes means you're having to eat at some ridiculous hour... but better safe than sorry.
Also I should add that my doc claims that you always wake up... but I'm not sure that's entirely true as mentioned above. Jwags is right as sometimes I do wake up in middle of a dream with one... not necessarily a nightmare for me though.