The Cadfael Chronicles are about a 12th century English monk who is the abbey herbalist and is depicted as effective at his job. Would an herbalist in England at that time have anything that actually works?

by ArmandoAlvarezWF

Edit: to give a fictional character his due, he's a Welsh monk who lives in England, not an English monk.

BRIStoneman

Hello, I wrote an answer here about 9th century medicine and pharmacology which is still broadly relevant to the C12th.

The tl;dr is that yes, even if medieval medicine doesn't quite match up to modern standards, a lot of its cures and treatments are based on real, observable science, and a lot of modern medicines are essentially just the refined versions of 'herbal' remedies. Bald's Leechbook, for example, prescribes wormwood tinctures for a variety of fevers and illnesses; wormwood is used today as a source of artemisinin - commonly used as a rapid response to malarial fevers - as well as an antihelminthic, a drug used to expel worms and parasites from the body.