Because of its immediate social significance, medieval sources provide a wealth of information on the theory and practice of Arabic medicine. In addition to numerous medical treatises, many sources also shed light on the lives of scientists, the professional medical communities, the social practice of medicine, the various healing institutions, and the regulation of the medical profession. Both the area and the period in which the Arabic medical tradition evolved are immense. In the ninth century Baghdad was the dominant center for the production of the Arabic medical tradition. In the tenth and eleventh centuries, however, many regional centers competed with Baghdad. In the thirteenth and fourteenth centuries, Syria emerged as the leading center in medical activities. During this period many medical institutions were built there, and a large number of physicians traveled from all over the Muslim world to seek employment in its institutions.

A shared Hellenistic medical legacy accounts for the apparent uniformity of Arabic medicine. The actual practice of medicine produced diverse and at times competing tendencies within this tradition. Insights into the rise of such tendencies can be pieced together from a variety of sources, including medical treatises, specialized and general biographical works, waqf charters,and market supervision manuals, as well as many anecdotes in literary and historical sources. These sources contain references to rudimentary medical practices among the Arabs before Islam, but an Arabic medical tradition per se, or even quasi-scientific medicine, did not exist.

The first references to learned medicine are under the Umayyad caliphate, which employed physicians trained in the Hellenistic tradition. In the eighth century a member of the Umayyad family is said to have commissioned the translation of medical and alchemical texts from Greek into Arabic. Various sources also indicate that the Umayyad caliph Umar ibn Abd al-Aziz (r. 717–20) commissioned the translation from Syriac into Arabic of a seventh-century medical handbook written by the Alexandrian priest Ahrun. As in the case of the other sciences, these early activities increased dramatically under the Abbasid caliphs of Baghdad, who employed Nestorian physicians from the city of Gundishapur. In particular, eight successive generations of the Bakhtishu family were favored physicians in the Abassid court well into the eleventh century. In addition to the learned practice of medicine, translations of medical texts and new medical writings started to appear in the ninth century. Most of these writings were based on Hellenistic medicine, but even in the very early period some new treatises contained original features that were not found in the earlier Greek sources. The most famous of the early translators and physicians are Yuhanna ibn Masawayh (d. 857), the head of Bayt al-Hikma, and Hunayn ibn Ishaq (808–873). With his students, Hunayn translated almost all of the then-known Greek medical works into either Syriac or Arabic.

At the same time these translations were made, original works were composed in Arabic. Hunayn, for example, composed a few medical treatises; of these, al-Masail fi al-Tibb lil-Mutaallimin (Questions on medicine for students) and Kitab al-Ashr Maqalat fi al-Ayn (Ten treatises on the eye) were both influential and considerably innovative. Although Hunayn's works included very few new observations, their creativity lies in a new organization, and in the case of the second book, in its deliberate attempt to exhaust all questions related to the eye. In any event, a solid command of medical knowledge was needed to produce these works. The most famous work of the early period was composed by Ali ibn Sahl Rabban al-Tabari (ca. 783–ca. 858), a Christian convert to Islam from Marv. Al-Tabari's book Firdaws al-Hikma (Paradise of wisdom) was the first comprehensive work of Arabic medicine that integrated and compared the various medical traditions of the time. This work adopted a critical approach to enable readers to choose between different practices. A section on Indian medicine provided valuable information on its sources and practices. Indian medicine was far less crucial than Hellenistic medicine in shaping the Arabic medical tradition, although occasionally physicians would compare Greek and Indian medicine and opt for the latter. This was the exception rather than the rule, however. The main role of Indian medicine was not to define the contours of the Arabic medical tradition but to set the tone for some of its initial interests and curiosities. Although the Greek scientific legacy was dominant, a mere awareness of more than one tradition encouraged a critical and selective approach that pervaded all fields of early Arabic science.

By the end of the ninth century the Galenic humoral system of pathology was completely integrated into Arabic medicine. Although extensive use was made of the writings of Hippocrates (fourth century B.C.E.), they were used within the more systematic theoretical framework of Galenic medicine. Humoral pathology was based on the notion of four humors (blood, phlegm, yellow bile, and black bile) and their relation to the four elements (air, water, fire, and earth), as well as to the four qualities (hot, moist, cold, and dry). The balance or equilibrium (itidal) of these humors and qualities amounted to health; imbalance, therefore, was considered to be the cause of illness and disease. Emphasis in treatment was placed on maintaining or reestablishing equilibrium by controlling the environment and the internal constitution of the body through the use of certain kinds of foods or medicines as well as through bleeding and purgatives. This system of medicine employed a significant degree of logical reasoning along with medical observation to explain illness and to devise treatment. Theoretical discourse was thus superimposed on clinical observation, and theoretical considerations played a major role in the structuring and organization of medical knowledge. Arabic medicine further developed this tendency to systematize and rationalize. For the first time, attempts were made to organize the vast body of medical knowledge in all branches of medicine into one comprehensive and logical structure.

An equally important trend focused on expanding empirical medical knowledge—with emphasis on clinical or case medicine—and on practical procedures for treatment, as opposed to the theoretical reflections on illness and health. One of the greatest representatives of this trend is the ninth-century scientist Abu Bakr al-Razi. In his prolific writings, al-Razi generated various theoretical criticisms of the body of inherited medical knowledge. More important than these criticisms, however, was his focus on method and practice. Throughout his work, al-Razi put more emphasis on observational diagnosis and therapy than on the theoretical diagnosis of illnesses and their cures. Al-Razi surveyed all of the available medical knowledge and then provided a critical review of this inherited knowledge on the basis of his own practice. His experience as a clinician was undoubtedly wide and rich; it was acquired in a long career as the head of hospitals in Rayya and Baghdad. Some of al-Razi's most original works also derived from this position. His Kitab fi al-Jadari wal-Hasba (On smallpox and measles) is the first thorough account of the diagnosis and treatment methods of these two diseases and the differences between their symptoms. A focus on clinical rather than theoretical issues is what characterizes this work and perhaps what makes it original. Al-Razi wrote many other medical treatises of considerable originality, covering such subjects as diabetes and hay fever. He also wrote an influential general textbook of medicine entitled Kitab al-Tibb al-Mansuri (The Mansuri book of medicine), which filled a vacuum because it provided a concise overview of medical theory that could be consulted by students and practitioners of medicine. The reputation of this book, however, has less to do with its original content than with its brevity and organization.

Al-Razi's most important work is his often mentioned but poorly studied book al-Hawi fi al-Tibb (The comprehensive book on medicine), an enormous work that in one incomplete copy fills twenty-three volumes. The book is not organized according to formal theoretical paradigms; rather, it is an encyclopedia of clinical medicine, including earlier writings on diseases and treatments as well as al-Razi's own clinical observations. In several places, al-Razi criticized Galen and stated that the reason for this criticism was that his own clinical observations did not conform with Galen's assertions. Al-Razi's meticulous documentation of his sources added to the merit of this work and made it a veritable treasure for the history of medicine. Al-Razi's primary interest was therapeutics, not the theoretical classification of medical knowledge. He did not devise treatments on the basis of logical inferences; rather, he conducted what often amounted to controlled experimentation. In the first volume of the book, for example, he traced the exact effects of bloodletting on treating brain tumor (sarsam). To do this, al-Razi divided his patients into two groups; he treated one with bloodletting and did not apply this treatment on the other. He then recommended a treatment method simply on the basis of the results of his observations. This and other examples illustrate that although al-Razi proposed no alternative theoretical framework, a considerable part of his research seems to have proceeded in practical neglect of Galenic theory. Theoretical medicine was simply irrelevant to al-Razi's rigorous research in clinical medicine. His most original contributions are undoubtedly in this field of clinical medicine.

The great al-Hawi of al-Razi was not without fault, however. Its main weakness was its enormous size and poor organization, which made the work inaccessible even to expert physicians. Because of these reasons, the work was not able to fill the demand for comprehensive but structured medical handbooks. Later in the tenth century Ali ibn Abbas al-Majusi (ca. 925–94) wrote Kitab al-Kamil fi al-Sinaa al-Tibbiya (The complete book of the medical art), also known as Kitab al-Malaki (The royal book), with the explicit intention of filling this gap. Al-Majusi praised al-Razi's work for its clinical comprehensiveness, but he noted its lack of a theoretical framework that could have provided structure and an organizational principle. Al-Majusi thus set out to write an accessible book that people could easily copy, buy, read, and use. His work was influential both in the Muslim world and later in Latin Europe.

In the same period an equally influential work was independently produced in Córdoba by Abu al-Qasim al-Zahrawi (936–1013); Kitab al-Tasrif li man Ajiza an al-Talif (Manual for medical practitioners), a large medical encyclopedia in thirty books, was intended as a synthesis of medical knowledge available at the time. The largest part of this work deals with symptoms and treatment, which reflects once again the increased interest among many Arab physicians in clinical medicine. The most popular and influential part of this work, however, is on surgery; this part, which was often copied separately from the rest of the book, provided detailed descriptions of medical operations, as well as illustrations of numerous surgical instruments. Further illustrating the practical trends in Arabic medicine, al-Zahrawi maintained in his work that the active practice of surgery was a prerequisite for theoretical knowledge of the field.

Although al-Majusi's work served as a popular handbook of medicine, it was soon replaced by what became the single most influential book on theoretical medicine in the middle ages and until the seventeenth century: al-Qanun fi al-Tibb (The canon of medicine) by the celebrated Muslim philosopher and physician Ibn Sina (981–1037). Ibn Sina composed several short treatises on medicine, including a popular didactic poem. His magnum opus Canon was written with the intention of producing the definitive canonical work on medicine, in terms of both comprehensiveness and theoretical rigor. In this book, Ibn Sina provided a coherent and systematic theoretical reflection on the inherited medical legacies, starting with anatomy, followed by physiology, then pathology, and finally therapy. Although he included many bedside observations and a few original contributions of a purely practical nature, Ibn Sina's main achievement was not primarily in the clinical domain. Rather, he produced a unified synthesis of medical knowledge, which derived its coherence from the relentlessly systematic application of logical and theoretical principles.

The fame of Ibn Sina's school of medical research often overshadows a significant tradition in Arabic medicine that although not completely innocent of philosophy practiced medicine essentially as a practical art. Medicine, according to this second tendency, was not primarily a matter of reflection on general rules and the deduction of particulars from them. Rather, for many Arab physicians, practice was the central concern of medicine. It is hard to find a physician during this time who promoted purely theoretical medicine without accounting for practical knowledge; it is equally hard to find advocates of pure empirical medical knowledge who were free of theoretical reflection. It is possible, however, to isolate tendencies that weigh in favor of either theoretical or practical medical knowledge. The careers of many physicians seem to have been disproportionately devoted to the cultivation of medicine as a practical scientific discipline. In Andalusia and North Africa, for example, after the end of the tenth century many physicians were also pharmacologists. This was the case of such famous physicians as Ibn al-Jazzar (d. 980) and Abu Marwan ibn Zuhr (ca. 1090–1162). In fact, the first criticism of Ibn Sina's Canon was written in Andalusia by another Abu al-Ala ibn Zuhr (d. 1131) of the same family of physicians, who objected mainly to the section that dealt with pharmacology because its exclusive theoretical nature reduced its practical usefulness. Abu Jafar al-Ghafiqi (d. 1165), another famous physician and pharmacologist, mentioned in one of his works that most physicians of this period prepared medicines themselves, suggesting that such practical know-how was part of what constituted appropriate medical knowledge. In contrast to abstract reasoning, experimenting with medicines as well as bedside observations was a common occupation among a significant number of physicians.

Anatomy was another field in which strong empirical tendencies were manifest. Quite understandably, the approach to surgery among most Arab physicians was cautious. Despite this caution, new surgical techniques were introduced in many fields; in ophthalmology, in particular, entirely new methods were adopted. Yet this advanced status of surgery does not in itself constitute evidence for the existence of a tradition of experimental anatomical discovery. Modern studies on Islamic medicine often assert that because of cultural taboos and religious restrictions anatomy was not pursued by Arab physicians, and that the notable anatomical observations were mere theoretical speculations on inherited anatomical knowledge. The most debated example of Arabic anatomy is the thirteenth-century discovery by the Muslim physician Ala al-Din Ali ibn al-Nafis (d. 1288) of the pulmonary circulation of blood. After obtaining his early education in Syria, Ibn al-Nafis moved to Cairo, where he pursued a career in Islamic law and medicine. Ibn al-Nafis wrote several commentaries on Ibn Sina's Canon. In his book Sharh Tashrih al-Qanun (Commentary on the anatomy of the Canon), he noted that Galen's and Ibn Sina's assertions that blood moves between the right and left ventricles of the heart through a hole between them was not correct. Anatomy, Ibn al-Nafis maintained, refutes this assertion because no such hole is detectable through anatomical observation. Ibn al-Nafis then argued that blood reaches the left ventricle through the lungs, thus providing the first explanation of the minor circulation of blood.

Despite some earlier reservations in modern scholarship on Islamic medicine, there now seems to be no doubt that the discoveries of Ibn al-Nafis had a definitive and decisive influence on the later European anatomical theories regarding blood circulation. A more controversial question is whether these discoveries are scientifically significant. Many studies (including those of the historian of Arabic medicine Max Meyerhof) have argued that Ibn al-Nafis’ discovery was a “happy guess” and could not have been the result of scientific anatomical experimentation. The basis for this argument is that because Islam prohibits dissection, Ibn al-Nafis must have relied on pure speculation. Yet even a cursory reading of Ibn al-Nafis’ work suffices to disprove this claim. In the introduction to his commentary on the anatomy of Ibn Sina's Canon, Ibn al-Nafis stated that both religion and general morality prevent him from conducting dissection. Yet the second chapter of this same book was devoted to the theoretical and practical benefits of dissection, and the fifth chapter discussed the methods and tools of performing dissection. More important, Ibn al-Nafis recurrently rejected or confirmed earlier assertions by referring to the results of anatomical observation, using such expressions as “anatomy (tashrih) falsifies what they say” or “anatomy confirms our findings and falsifies their view.” Furthermore, as an indication that he is not referring merely to inherited anatomical knowledge, Ibn al-Nafis often said that he observed certain things recurrently and did not find them in conformity with earlier accepted theories. There seems to be no doubt that despite some restrictions, early Arab physicians performed dissection, and used it to develop medical knowledge.

In addition to Ibn al-Nafis, there are many other references to practical anatomical observations. Disagreements with Galenic accounts of muscle and bone anatomy, for example, could not have derived from philosophical speculation. In the twelfth and thirteenth centuries Abd al-Latif al-Baghdadi provided yet another model through which ancient anatomy was criticized and developed. Al-Baghdadi wrote a description of a famine that occurred in Egypt in 1200. In that description he reported that after examining a large number of skeletons, and after asking other people to conduct their own independent examinations on other skeletons, he arrived at the conclusion that Galen's description of the bones of the lower jaw was erroneous. Although this correction did not amount to a complete rejection or reformulation of Galenic anatomy, it does demonstrate a readiness to question this anatomy on the basis of experimental anatomical examination.

The significant contributions of al-Baghdadi and Ibn al-Nafis did not occur in a vacuum. The twelfth and thirteenth centuries witnessed a surge in medical activity, as physicians from all over the Muslim world sought careers in the medical institutions at Damascus and Cairo. At the social level, physicians were closely integrated with the rest of society, and many of them were leading authorities in the religious disciplines as well, especially law. Ibn al-Nafis, for example, was a scholar of hadith (the verified accounts of the actions and sayings of the Prophet Muhammad). Diya al-Din ibn al-Baytar (ca. 1190–1248), one of the leading physicians and botanists of the period, was also a leading jurist who collaborated in his medical research with a circle of Syrian and Egyptian Hanbali scholars (one of four schools of law of Sunni Islam). In Cairo this circle included Abu al-Faraj Abd al-Latif ibn Abd al-Munim al-Harrani, the leading Hanbali jurist of the time. Such profiles suggest the increasing social prestige of larger numbers of physicians and a higher degree of participation in the profession by larger and more representative sectors of society. The first references to a madrasa-like institution (a college whose primary purpose is the teaching of Islamic law) for medical learning also came from this period. In thirteenth-century Damascus, Muhadhdhab al-Din al-Dakhwar endowed a school for the exclusive teaching of medicine. The school was inaugurated by the city's leading religious authorities and attracted many religious scholars as students; leading religious figures filled the prestigious position of head administrator of this school. There are also several references to medical instruction in religious schools. Al-Dakhwar himself was a distinguished teacher of a generation of accomplished physicians including Ibn al-Nafis. As a result of the enhanced social status of physicians in this period, another student of al-Dakhwar, Ibn Abi Usaybia, decided to compile a bibliographical dictionary for physicians, who were now fully recognized as members of the social elite.

The prestige of the medical profession increased but did not start in the twelfth and thirteenth centuries. This prestige was closely dependent on mechanisms of social and professional integration, most notably through hospitals. The hospital is one of the greatest institutional achievements of medieval Islamic societies. Between the ninth and tenth centuries five hospitals were built in Baghdad, and several others were built in other regional centers. The most famous of these was the Adudi hospital established under Buyid rule in 982. After this period the number of hospitals increased significantly, when such famous institutions as the Nuri hospital of Damascus (twelfth century) and the Mansuri hospital of Cairo (thirteenth century) were built along with others in Qayrawan, Mecca, Medina, and Rayy, to name a few.

These institutions were open to everyone who needed medical care, regardless of gender, religion, age, or social class and wealth. Medical care was also provided to prisoners, and mobile clinics were regularly dispatched to remote villages. Many of these hospitals were divided into different sections: men and women were treated in separate halls; special areas were reserved for the treatment of contagious diseases; there were also separate areas for surgical cases, and others for the mentally ill. The hospitals also had living quarters for the physicians in attendance as well as for other members of the service team. Some hospitals had their own pharmacies and libraries that could be used for medical instruction. Clinical training and bedside instruction were often provided in these hospitals. A chief administrator, who usually was not a physician, was in charge of hospital administration, while a chief of staff, who was also the head physician, was in charge of running the medical operations. Many of these hospitals had enormous operating budgets, which were usually derived from the revenues of waqf properties dedicated for hospitals. Such revenues were spent on the maintenance of the premises and the staff, as well as on the cost of treatment, which was provided to patients free of charge.

Although hospitals provided the most structured framework for the regulation of the medical practices, there were other means through which such regulation was attempted. The muhtasib (market supervisor) was a public officer, who was in charge of guarding against fraudulent practices and cheating in all public professions and crafts, including medicine, surgery, and pharmacology. Hisba (market supervision) manuals were compiled, outlining the duties of the muhtasib. References in such manuals to the medical profession appear only after the eleventh century, but other sources refer to earlier instances of testing of medical doctors by a chief physician (Ra’is al-Attiba) who worked in collaboration with the state authorities. Several treatises that outlined the subjects in which the physicians ought to be tested were also composed. Although the sources do not mention many actual cases of testing and examining, it is likely that at least some such testing must have taken place to generate the considerable literature on this subject. Although this testing did not amount to an organized system of licensing, it certainly provided theoretical norms, the systematic application of which depended on the general stability of social institutions at any particular historical moment. An even less organized form of regulation was provided through the abundant literature on medical ethics. Influenced by Hippocratic and Galenic writings, this literature dealt with appropriate codes of professional conduct. Such nonenforceable but highly normative codes were also passed on through teaching in hospitals, special schools, madrasas, and mosques, and within families of physicians. Taken together, these social practices afforded Arabic medicine a level of organization unprecedented in history that contributed to the further development of the Arabic medical tradition.