I have hypoglycemia and definitely know how it effects my mood. I have to eat (even just something small) every 3-4 hours or so, more often when I'm working out hard. I've been so dizzy waking up in the morning that I've almost passed out and have a hard time walking to the kitchen - almost like being drunk but far less pleasant. I might not realize it right away, but when my blood sugar gets low, I get moody, sometimes very much so if I start to get dizzy/tired and can't get to some kind of sugar/food right away.
My dad is hypoglycemic and we have similar symptoms like shaky hands, mental fog, tiredness, etc., but a bit less of the moody stuff generally than me. I knew the doctor was going to immediately jump to depression, which does seem to sound legitimate if your symptoms are that extreme, but for me and probably many others with this; just eating something small helps when you feel it coming on. I know I've gotten really snippy unjustly with people before when my blood sugar was low, so I keep 6oz V8 cans, 6oz pineapple juice (kicks in quickly), and Odwalla bars, etc., in my car so that I can just run and grab one to hold me over til I can eat enough. I know what it's like because I'm overall a pretty positive, happy person, and it takes a lot for me to be in a bad mood. Having really low blood sugar has been enough for me to get moody over nothing. Luckily I manage it better now and am self-aware enough to catch it most of the time before I get rude and control it til I can find something to bring my sugar back up to normal.
Hope this helps. Good luck.