It is preferable to consult trustworthy Muslim doctors (regarding things that may affect a patient’s performance of religious duties). But if there is no Muslim doctor available, a patient may resort to a non-Muslim doctor who is trusted and follow his instructions.
Sheikh Ibn `Uthaymeen (may Allah have mercy upon him) stated that: “Some scholars are of the opinion that so long as the doctor whom a patient has consulted is trustworthy, his instructions are to be followed, regardless of whether or not this doctor is Muslim.
According to those scholars, this opinion is derived from what the Prophet (peace and blessings be upon him) did when he (peace and blessings be upon him) hired a disbeliever guide called `Abdullah ibn Urayqit to show him and Abu Bakr (may Allah be pleased with him) the way from Makkah to Madinah. The Prophet (peace and blessings be upon him) trusted that guide at a time when the disbelievers were offering a reward of two hundred camels to whoever would seize him and his companion Abu Bakr and bring them back to Makkah. He (peace and blessings be upon him) did so because he (peace and blessings be upon him) saw that that guide was trustworthy and could be counted upon in spite of being a disbeliever.
Based upon this act of the Prophet (peace and blessings be upon him), it was said that a patient may accept the advice of non-Muslim doctors, since they are honest with him. Moreover, we know that there are non-Muslim doctors who are more honest and qualified than some Muslim doctors. This has nothing to do with their religious attitude as much as it has to do with their keenness to preserve good reputation among people.
Based on the above, a Muslim patient may follow the instructions of a non-Muslim doctor who is honest, even if this doctor has told him that he should not stand while praying because it would be harmful to his health. This is also the case if an honest non-Muslim doctor has advised the Muslim patient not to fast lest it may worsen his health.”