Arabic is a very rich language. Just ask any Arabic speaker, and they will tell you Arabic is the richest and most beautiful language on earth. Now, it is obvious anyone would say their language is the most beautiful and the richest, but what makes Arabic unique are the countless images you can see in your mind if you close your eyes from time to time as you read. All you have to do to get a sense of that richness is read the Holy Quran or even pre-Islamic Arabic poetry. Hundreds of years before the famous literary piece of Beowulf was written, which is regarded a milestone in the development of the English language, Arab poets were traveling across the Arab peninsula, reciting their unique metaphoric poems. During that pre-Islamic period, Arab poetry saw the proliferation and development of sophisticated poetic and literary instruments that are still being investigated and used to this very day. It was only toward the end of the 7th century and the beginning of the 8th century that written (literary) Arabic was consolidated not only as a means of spreading the Quranic text but also to establish the governmental bureaucracy that would develop in the following centuries and absorb words from other languages, such as Persian.
But literary Arabic, that of the Quran and ancient poetry, isn't the same as spoken Arabic. In fact, Arabic is diglossic, which means there are two distinct varieties of this language. Spoken Arabic varies by region, sometimes even between regions just a few miles apart. These versions of Arabic spoken in different regions are referred to as dialects, which differ not only in their pronunciation, but sometimes even in their syntax and vocabulary. As opposed to that, Literary Arabic is almost the same across the Middle East since it has been used for centuries to consolidate the language of official decrees, documents, registries, as well as sciences, arts, poetry, etc. There are hardly any differences between Arab countries when it comes to literary Arabic, except for differences in jargon or terminology, but the long and short of it is this: if you have a document written in literary Arabic, it can be read in any Arab country.
Another aspect to consider is this: Since spoken Arabic is… well, spoken, it is a native tongue; literary Arabic is not. It can be spoken, of course, but you simply cannot walk the streets in any Arabic-speaking region and address people in literary Arabic. This language is regarded of very high register and is reserved for news broadcasts, official interviews, the written, official media, literature, poetry, etc. Children do not speak it at home; they start learning its alphabet at school. This means that proficiency in spoken Arabic does not guarantee proficiency in literary Arabic. In other words, literary Arabic is the second language of native Arabic speakers. This is one of the main mistakes made by translation agencies: They look for translators who are native speakers of Arabic as a prerequisite without looking into the translators' education. In fact, one does not have to know spoken Arabic to master literary Arabic. It all depends on immersion, the same as with any acquired language.
My next point applies in particular to the field of medical translation: Many agencies require that the Arabic translator be a trained physician or pharmacist. What these agencies do not consider is that the vast majority of the institutions that train and qualify physicians, pharmacists, and other healthcare professionals in Arab countries neither use nor teach medical terminology in literary Arabic. If you study medicine in Jordan for instance, you read materials mostly in English and French. You also need to know spoken Arabic, of course, but the terminology is not discussed in literary Arabic. The same goes for Arab physicians trained and qualified in Israel: They are not necessarily familiar with the correct medical terminology in literary Arabic.
So, to conclude, if you are looking for an Arabic medical translator, here are three points to consider:
He, or she, needs to be proficient in literary Arabic (spoken Arabic is insignificant, unless the text is intended for certain populations, such as young children).
They need to be experienced and trained translators.
They need to be familiar with medical terminology.