While interest has been faltered across the UK, it has proved particularly low north of the border, organisers said.
A spokeswoman for Sport Relief said: "The official launch date of this year's campaign was 21st January, however the weather conditions have affected the amount of people signing up to fundraise for Sport Relief. This is a particular problem in Scotland."
This year, in addition to runs, people will also be able to swim or cycle over a variety of distances as part of the Sainsbury's Sport Relief Games, which take place between Friday March 21 and Sunday March 23.
For more information visit www.sportrelief.com.