On the one hand, your average medical practitioner of today has a wider range of options that will Actually Work on their patients compared to a Medieval medical practitioner. On the other hand, that does not write off a Medieval medical practitioner as entirely useless. More can always be said re Medieval medicine, which has an undeserved bad place in popular understanding, so if anyone would like to write up a post of their own, please don't let this post stop you!

For the meantime, OP, here are some previous posts re this matter:

• u/BedsideRounds has a non-exhaustive list of Stuff That Worked;

u/sunagainstgold talks about:

• medicine and its efficacy;
• medical education in the Late Middle Ages;
• and various solutions to the removal of arrows, including the case of Henry V.

But the star of this post is u/BRIStoneman drawing from the 9th Century medical text Bald's Leechbook:

• On the book's attitude to the treatment of medical conditions in general;
• On the treatment of infected wounds;
• On its recommendations for cuts and fevers (with bonus literacy downthread);
• An assortment of treatments demonstrating that the leeches of Early Medieval England were on to something;
• On its treatments for worms of all kinds;
• On its treatments for eye infections, including one that, surprisingly, works against MRSA.

Bonus: Bald's Leechbook is available in all its digitised glory here.

My area of expertise is Chinese medicine, and I think people really underestimate the complexity of the medicine, their nosology and approach to treatments. So, I will post some case studies from Asaf Goldschmidt's translation and commentary of Medical Practice in Twelfth-century China –A Translation of Xu Shuwei’s Ninety Discussions [Cases] on Cold Damage Disorder

Case #3: Manifestation Type [Requiring Treatment with] Magnolia Officinalis and Apricot Added to Cassia Twig Decoction 桂枝加濃樸杏子湯證 In the first lunar month of 1128, there was a military official in the city of Yizhen who fell prisoner of Zhang Yu. He was held captive and was tied day and night [in the storage space] beneath the deck of a large ship, where he could not stretch out.

After several days, he managed to escape. [Following his escape] he ate his fill, disrobed, and picked the lice off his body, after which he was quite comfortable. The next day, he came down with a Cold Damage disorder. A certain physician thought that he had become sick because he had overeaten, and purged him [to expel the excess]. Another doctor thought that when he disrobed he was hit by pathogenic [qi]. Consequently this doctor applied a sudorific [to expel the pathogen]. After the patient had received such miscellaneous treatments over several days, he gradually became confused and sleepy. He had upper panting and high breathing. The doctors who treated him were panicked, not knowing what caused this disorder.

I examined him and said: ‘This is a Mature Yang [circulation tract] disorder, one needs to purge it. When the exterior aspect is not resolved and the patient experiences slight panting, Zhang’s method is to use Cassia Twig with Magnolia Officinalis and Apricot Decoction.’ A doctor challenged me: ‘In my whole life, I have never used a Cassia Twig [Decoction]. Moreover, this medication is heating. How can it cure panting?’ I replied ‘This is not something you know about.’ After I administered one dose [of the decoction], the panting subsided. Upon administering a second dose, much sweat poured out. By evening, the patient’s body was cooler and the vessels were already harmonized. The other doctor said ‘I did not know that Zhang’s methods are as divine as this.’ I said: ‘How could his method have deceived and confused later generations? People seldom study [this topic], so they have no way to comprehend it.

So the formula here he used is from Discussion on Cold Damage 215 CE.

This is another discussion of a case in which no treatment was applied as the patient appeared beyond saving

Case #27: Manifestation Type of the Tongue Curled Back and the Scrotum Retracted 舌卷囊縮證 In Jurong County [present-day Jiangsu Province], a son of the powerful Li family contracted a Cold Damage disorder. His hands and feet were cold, he felt as if his qi went up and rushed into his heart, he was hungry but did not want to eat, and his pulse was tense and strung. I examined him and said: “The Attenuated Yin tract is completely full, and the circulation vessels are overcome [?]; this is the most dreaded [of the Attenuated Yin syndromes], that of the tongue curled back and the scrotum retracted.” On the next day, the patient’s tongue curled back and the he died.

Here, attenuated yin is a name given to one of the channels called Jueyin. That is a bit of a strange translation.

This is another case, which appears to be similar to the disease of jaundice

Case #46: Manifestation Type of Eruption of Yellow Color 發黃證

In the fifth month [of the year 1130], I relocated to Lishaozhong, in the eastern outskirts of Weiyang. A child of a prominent family had been sick with Cold Damage disorder for 8 or 9 days. His whole body was yellow in color, his eyes and nose both were painful [or, yellow], his two arms, nape of the neck, head, and waist were all stiff, his stool was rough [i.e. painful to pass], and the color of his urine was like golden yellow. I examined him and said: “The pulse is not only tense but accelerated. The patient’s disorder originated when a moisture [pathogen] that injured the Spleen functions. The [latent] hot summer’s qi in the foot Mature Yin tract struggled with the long-retained food [in the Stomach], which became stagnant and steaming, unable to drain downward. As a result, the head and the face sweat but from theneck down there is no sweat. If the qi inside the nose is cold, and when palpating the radial pulse from the Inch-mouth position toward the palm there is no pulsation, the patient will die. At present, the pulse and the manifestation type correspond.” I administered both Artemisiae Scopariae Decoction and Five-Ingredient Powder with Poria. After a few days the patient recovered.

So now the question is Artemisiae Scopariae (Yinchen) reliable at treating diseases? According to Cai et al (2020)

• Cholestasis contributes to the progression of liver diseases.
• Therapeutic options for the treatment of cholestasis are limited.
• Anti-cholestasis effect of Artemisiae Scopariae Herba is better than other therapies.
• Nature products in Artemisiae Scopariae Herba are potential hepatoprotective drugs.

Should also be mentioned Zhang Zhongjing also recommended formula with Ginger for nausea during pregnancy, according to Thomson et al (2013) "Despite the widespread use of ginger in the diet, its clinic value and safety profile in treating NVEP is still unknown. Our meta-analysis suggests that ginger is an effective nonpharmacological treatment for NVEP."

I would suggest Asaf's book, of which they are 90 cases.

This is book discussing physician Wang Ji and his cases, but I'm not familiar with the contents, apologies.

Sources

Effects of Ginger for Nausea and Vomiting in Early Pregnancy: A Meta-Analysis by Maggie Thomson, MD, Renee Corbin, MSc, and Lawrence Leung, MBBChir, MFM(Clin)

Medical Practice in Twelfth-century China – A Translation of Xu Shuwei’s Ninety Discussions [Cases] on Cold Damage Disorders, Asaf Goldschmidt Springer, 2019

Recent progress in the study of Artemisiae Scopariae Herba (Yin Chen), a promising medicinal herb for liver diseases by Yajie Cai, Qi Zheng, Rong Sun, Jiarui Wu, Xiaojiaoyang Li, Runping Liu, Biomedicine & Pharmacotherapy, Volume 130, 2020