Hi, Linda! The wonderful Google community beat us to the punch. They are correct; a room with "G" in the name means that it is on the hospital's ground floor. Thank you for the question. Take care, and God bless!
If you mean like G203. It just stands for the Ground floor in that building.
It means your room will be on Ground floor.
Ground floor
Ground level
Thanks! Your answer is awaiting moderation.