Scotland's largest health board has temporarily suspended all out-of-hours services at five centres due to a lack of available GPs.
NHS Greater Glasgow and Clyde (NHSGGC) said the move was "the only option" which would allow the service to continue across west central Scotland.
The Queen Elizabeth University Hospital in Glasgow is among those affected.
The others are Inverclyde Royal, Gartnavel Royal, Greenock Health Centre and Easterhouse Health Centre.
Out-of-hours overnight services will continue at Stobhill, Victoria, Royal Alexandra and Vale of Leven hospitals during the week.
Accident and emergency
With the exception of Vale of Leven, these centres will also be open during the evening and at weekends.
Patients are referred to the primary care centres by NHS 24 when their GP surgery is closed and they are too ill to wait until it reopens.
In June last year, NHSGGC said it had to temporarily withdraw weekend out-of-hours services as it did not have enough doctors "willing to work" between midnight and 07:59.
When a similar situation emerged in 2018, patients requiring urgent medical care were asked to go to accident and emergency.
Others were asked to wait until the out-of-hours centres opened again at 08:00.
The health board said the latest temporary closures were caused by national changes to GPs' pensions and terms and conditions, as well as "local operational issues".
This had led to short-notice centre suspensions "resulting in an inconsistent and unsustainable service".
Kerri Neylon, primary care lead GP at NHSGGC said: "Temporary consolidation of services is the only option which will enable us to continue providing this crucial service in the immediate future.
"This formalises the ad-hoc arrangement which has increasingly become the norm in recent months and provides patients and staff with certainly and reliability.
"We are absolutely committed to delivering a long-term sustainable, safe and reliable out-of-hours service to patients across Greater Glasgow and Clyde."
He added: "The long-term delivery model, which uses new technology alongside smarter recruitment, is demonstrably the best way to meet demand.
"We are working to implement those changes as quickly as possible and we are acutely aware of the need to do so. There will be regular updates on progress."