If it is a municipal hospital, there are doctors and nurses on duty in every department on Saturday and Sunday.
If the hospital you are choosing is a private clinic, or a small township hospital, you will have to ask in advance if there is a doctor on duty on Saturday and Sunday.
Just because there are fewer staff on Saturdays and more people visiting the doctor, the wait time for either lab tests or queuing up to see the doctor may be a bit longer than usual.