My doctor has just prescribed me 100mcg Vitamin B12 supplements - has anyone else taken these? If so, how quickly did they kick in? I've been having pins and needles for the last few months and my doctor has referred me to see a neurologist (eek) but wants me to take these in the meantime as my levels were slightly, but not very, low at 400. Grateful if anyone with experience can let me know how soon I could expect an improvement if B12 were the culprit? I really hope it is! Thank you 