Opening hours for the Minor Injury Unit (MIU) at Honiton Hospital are to be temporarily reduced on Wednesdays and Thursdays.
From Friday to Tuesday, the MIU will open from 7.30am to 11pm as usual.
On Wednesdays and Thursdays, the MIU will operate with reduced hours from 10am to 6pm.
The changes come into effect from Monday 10 December and will continue for at least eight weeks.
The new times have been widely publicised to GPs, NHS Direct and the ambulance service, and have been placed on notice boards at the hospital. NHS Devon has been notified.
The nearest alternative minor injury services are at Exmouth Hospital or the walk-in centre at RD&E.
The Trust has been forced to reduce the opening hours due to unavoidable staff absences, including sickness.
The weekend-midweek pattern of opening hours has been planned to reflect peaks in activity.
Kate Lyons, the Trust's director of operations, said: "We apologise for any disruption the temporary reduction in opening hours may cause.
"Decisions such as this are not taken lightly – and the safety of our patients is our number one priority.
"While temporary measures like this are not ideal, the Trust's view is that it is not acceptable to keep an MIU open with unsafe staffing levels.
"Wednesdays and Thursdays are traditionally our least busy days, so reducing the hours on these days will have the least impact on patients."