I know Greek people here in Canada, but I'm not sure they'd be up to translating complex medical instructions. Most people don't know what platelets are in English, let alone in another language. However, that being said, I think the idea of taking a letter like that along is a good one and there must be businesses or services that would translate it for you. Here, the hospitals have an extensive system of translators, so that might be one place to start looking, especially if you went through Dougie's doctors. That way you'd find someone who might have the medical terminology for something like that. Another place to look would be around universities. There used to be academic journals in languages other than English and occasionally translation would be necessary.
Lily