As per Saudi labor law, every employer is supposed to take care of his employees' medical needs. Medical insurance, which is big business in Saudi Arabia, has now become compulsory. I would advise all people looking forward to working in Saudi Arabia to read and re-read their contract for this particular point. Please note that unless it is explicitly mentioned in your contract that you would have to pay partly for your medical expenses, it is the responsibility of your sponsor to foot all your medical and dental bills.
It is a prevalent practice among some hospitals to make the patients pay a minimum amount, usually SR20, for every visit to the hospital. This depends on the type of insurance card. If you are a family of four, and theoretically speaking if all of you visit the hospital once a month, remember that it comes to a substantial amount every year. But this amount also must be reimbursed by your sponsor legally because, as mentioned earlier, if it is not mentioned in writing in your contract, your employer has to bear 100% of your medical and dental bills.