The adult female lurcher, now named Bella, was found in a field near Greenways in Newton Flotman on Friday morning (4 March).
The concerned member of the public rushed Bella to the local vets in Long Stratton where she received immediate treatment.
RSPCA inspector Laura Sayer said: “When I arrived at the vets on Friday afternoon I was shown poor Bella. She was in extremely poor body condition and was so weak she could hardly stand.
“She had no interest in her surroundings, people or even food - all she wanted to do was to lay down.”
Due to her condition, vets believe Bella has been neglected and the RSPCA is appealing to the public for any information.
Inspector Sayer said: “Anyone with any information is urged to call me on our inspectors’ appeal line in complete confidence on 0300 123 8018.”
She added: “Bella’s condition is said to be improving and thankfully her appetite has returned. The last update I received was from the veterinary nurses who said "she's eating us out of house and home!”
The RSPCA is a charity and rely on public donations to exist. To assist Inspectors in carrying out their vital work please text HELP to 78866 to give £3 (Texts cost £3 + one standard network rate message).