Medicine in the Muslim regions was at once better and slightly worse than in the Christian areas. In the academic realm, all the best books were in Arabic, and the cutting-edge research (such as it was) was too. But at the day to day treatment and care level, medical practice was in general more passive in the Muslim regions. The difference may not have been great, since effective medicine was generally lacking. Passivity for philosophical reasons probably also varied with place, time, and person (same as with anything).
My comments in this article are based on general knowledge from many sources, and specifically on the Tibb al-A’imma, an Ismaili (Shi’ite) collection of medical advice. You can find this document here: https://www.al-islam.org/printpdf/book/export/html/41434
Most of Europe and the Middle East accepted the Greek doctrine of four humors. This framework was simply Science, their construct of how things worked. Bodies, climates, foods and herbs, were divided into hot and cold, wet and dry. The Tibb al-A’imma notes that, of course, medical treatment had to take climate into consideration. A cold rainy place like Paris needed different medicine from a hot dry place like Cairo.
The Muslim philosophical tradition was ambivalent about intervening in disease. Religious leaders had been respected as physicians, so there are sayings from the Prophet, his Companions, and leading men (including the others in the line of 12 Imams) explaining the connection between physical and spiritual. The Tibb al-A’imma notes that emotional and mental sources of stress could cause physical symptoms, which is why its writers generally justified the use of charms which addressed the beliefs of the sufferer. The key point was that the charms had to be phrases from the Quran, to make sure that nothing illicit was allowed. Christian use of charms followed the same principle, but the Islamic charms may have been more strictly straight out of the Quran than the syncretic Christian charms.
Islamic philosophy saw pain as a way to expiate sin. One saying notes that “a night of fever expiates a year of sins.” Because the soul’s health mattered most, a doctor might hesitate to relieve pain when it was better for the patient to suffer patiently. In practical terms, a physician probably used whatever herbs for pain that he could supply, without hesitating, but the philosophy supplied him with reasons to feel less urgency about curing a pain at all costs. Some pains were direct rebukes from Allah, so should these be cured at all?
Perhaps for this reason, Islamic medicine focused primarily on prevention. Good health came from eating little and abstaining from various excesses, and also from strong faith. Strong faith meant not going to doctors. The Tibb al-A’imma praises those whose faith was so strong that they were rarely sick and never called doctors. The four humors theory, of course, also focused on prevention. Eat for your physical type and climate, which is the will of Allah anyway. It was not clear what was the will of Allah for the sick, but for the healthy, it was clear, so squandering your health with overeating was seen as close to a sin. Prevention and piety were hand in hand.
The hadiths about medicine were evaluated not for success in healing, but as hadiths were in general: by who had transmitted them, and how. Pragmatic success was not a way to judge skill, as illustrated by a hadith of the Prophept. A man asked Mohammad about his brother’s abdominal pain, and the Prophet suggested honey in hot water. The next day, the man reported that it had not helped. The Prophet said that Allah does not lie, but the brother’s belly could. Privately, he told his followers that this man must be a hypocrite, and medicine could never help such a one.
One of the points of dispute among Muslim physicians was in the role of wine in medicine. It was the base fluid for many, if not most, Christian herbal medicines. We moderns can’t help pointing out that alcohol kills germs. But since the Prophet had forbidden wine, most Muslim doctors held that no, it could not be used as medicine. Why would Allah use something forbidden to heal? That made no sense.
Islamic medicine may have focused more on bleeding and cupping than Christian medicine at this time. It certainly recommended these remedies, cautioning that recitations of the Quran had to be pronounced over the flowing blood. I wonder if treating blood this way became a more common practice when mixtures with wine were prohibited, and also I wonder if bleeding came into European early modern medicine mainly through the Arabic medical texts. But I haven’t researched these questions.
Herbal treatments and accompanying charms were not very different from those we saw in Bald’s Leechbook, accounting for different climates and plants. One of the Imams left us a treatment for phlegm: Equal parts of Byzantine mastic, frankincense (a major product of the Arabian peninsula), thyme, bishop’s weed, and fennel were ground into powders, sifted, and combined. This mixture was added to honey, to be taken twice a day.
Quran-based charms were also similar in spirit. One charm for tooth pain in Timm al-A’imma says to take 3 olive leaves and write on each one, “In the name of Allah. There is no sovereign greater than Allah, the King, and you are his Khalifa. Ya Haya Sharahiyya, remove the illness and send the cure, may Allah bless the Prophet and his family.” A note explains that Ya Haya and Sharahiyya were names of God from Hebrew. (Ya Haya must be the four-letter name of God that we render Jehovah, but I can’t place the other.) A further instruction to make the charm better suggested putting the olive leaves into a cloth, and tying the cloth with seven knots, and naming each knot after one of the prophets: Adam, Nuh (Noah), Ibrahim, Musa, Isa (Jesus), and Shuayb (?). The cloth was to be attached to the tooth while praying for peace on the Prophet and his family.
I doubt that the differences in medical philosophy meant much for the health of a population during the main medieval centuries. It was in the following centuries, the Renaissance to Early Modern periods, that it mattered. European medicine became based on dissection and experimentation with herbal chemicals, but Islamic medicine was forbidden to pursue dissection, at least. Europe’s Christian philosophy promoted intervention in nature’s ways, perhaps based on how the stories of the saints showed them putting out fires and curing diseases. If the saints changed the course of nature, how could it be wrong to imitate them? This early stage laid the foundation for modern science.
People often ask why the Muslim world, with its base of Egyptian, Persian and Indian sciences, fell behind after the close of the Middle Ages. I think here is one of the reasons: the rise of scientific medicine was not something Islamic philosophy could at first accept, especially as embodied by the Ottoman Empire of the 16th and 17th centuries. The Empire was wary of innovative religious ideas, because they had learned the hard way that such things led to revolts. It preferred a uniform and change-resistant set of religious beliefs and practices. At the same time, Europe was exploding into diversity of opinion and practice in the Reformation. Europe paid in massacres and persecutions, but it also made space for intellectual innovation that broke previous religious barriers in medicine.