Scotland could be short of at least 500 doctors by 2020, according to figures compiled by the Royal College of General Practitioners Scotland (RCGP Scotland).
It has called for immediate action on the issue to save the current GP system.
The number of retiring and emigrating GPs combined with a population increase will require an additional 563 GPs by 2020, RCGP Scotland predicts.
The Office for National Statistics (ONS) figures expect the Scottish population to grow by a minimum of 123,000 people up to 276,000 people by 2020.
Added to that about 20% of the GP workforce is aged over 55 and likely to retire in the next five years.
Dr Miles Mack (pictured), the chairman of RCGP Scotland, said: "We need up to 915 more GPs in the next five years [if the population grew by the predicted maximum amount] or we face a very different 2020 Vision than the Scottish government would wish to report.
"We need immediate action and radical thinking if we are to save the system we have been so justly proud of."
However, Health Secretary Shona Robison said that the number of GPs employed in Scotland has risen by 6.9% to nearly 5,000 during the last five years.
"We have also increased funding by 10% and there are more GPs per head of population in Scotland than in England,” said Robinson adding that the recently agreed GP contract aims to give the profession stability over the next three years.
The Royal College has also demanded more information on the whereabouts of the £40m allocated by the Scottish government for primary care in 2015/16, and announced in November last year.