hi cheng,

there are plenty of accredited medical clinics by the Qatar Embassy.

I had mine at St. Peter and Paul Medical Clinic, Grey St. Malate.
you have to bring 6pcs of passport picture.

after you get your medical results, produce a photocopy of it your Visa Notice from MOI, and your passport. Bring it to ANY WWWExpress branch because you need a Visa Certification to be presented to the Philippine Airport Immigration. If you don't have that, they won't allow you to go out of the country...

hope this helps ;)