ISO 13485 certifies the quality management system — how a facility designs, documents and controls its process for medical devices, from raw material intake to post-market complaint handling.
WHO-GMP looks specifically at the manufacturing environment: cleanroom classification, equipment qualification, personnel hygiene and the physical conditions under which a batch is actually produced.
A facility can hold one without the other. We carry both, because a buyer asking for either should get a straight answer, not a redirect to a different certificate that sounds similar.