You do not require a doctor's sickness certificate for any illness lasting seven days or less. Your employer may however require you to complete a self-certification form (SC2) which is available from your employer or on the HMRC website.
If you are sick for more than seven days, your employer can ask you to give them some form of medical evidence to support payment of SSP (statutory sick pay).
This can be requested at reception. If the doctor has not seen you for this illness they may call or arrange an appointment.
If you have an existing sickness certificate and think you will need to be off work for longer:
Please contact the surgery at least one week before your sick note runs out.