Pilots are currently planned to go live in Hillingdon, Kensington and Chelsea, Hammersmith and Fulham, and Westminster in November.
NHS 111 will also be launching in north east London in February 2012, in Redbridge and Waltham Forest as well as Barking and Dagenham and Havering.
GP surgeries in the pilot areas will now be advised to signpost patients to the service, including flagging up its availability on practice telephone answering messages. GP surgeries will also be provided with information for patients.
But some practices in Hillingdon have also signed up to allow NHS 111 call handlers to directly book GP appointments for callers.
NHS 111 services are already live in four pilot areas - County Durham and Darlington, Nottingham City, Lincolnshire and Luton.
The number is designed to be used by patients requiring medical help or advice in non-life-threatening situations.
GPC leaders have warned that once funding for the pilot schemes dries up, funding could be diverted from other services, including primary care out- of-hours services.
The GPC has also warned that NHS 111 services can drive up costs because call handlers aim to deal with patients in a single call, and may be more likely to refer them to hospital as a result.