Some visa applications require that you undertake a medical examination and/or chest xray. You can find more information about the health requirement here:
Undertaking the medical before lodging a visa application
The medical examination can take some time to be finalised, so you may wish to undertake your medical examination prior to lodging your visa application in order to minimise any processing delays and to ensure your visa application is finalised as soon as possible.
If you wish to undergo your medical examination before lodging your visa application, you will need to complete the My Health Declaration (MHD) form on the DIBP website, to receive your HAP Identification Number, before you make an appointment with one of DIBP’s panel physicians: My Health Declarations
All medicals and chest xrays must be done at a panel physician appointed by the Department of Immigration and Border Protection.
You can find a list of panel physicians by country here: Panel Physicians - By Country