I have a yorkie roxy 5 months and she has low blood sugar. is this normal?

i had this yorkie for about a month now and i call the vet and they said that she needs to eat more times aday. i asked the lady that i bought the dog from and she said it was normal for little dogs. roxy only weights 3 pounds. i bought this stuff that she takes 3 times aday and she seems to be doing alot better. i always had big dogs nothing this little and i wonder if this is normal?