In the second instalment of a four-part Health Matters series on traditional Chinese medicine, Aidyn Fitzpatrick investigates the drug-interaction risks of combining Chinese remedies with Western medicine, and how Hongkongers can protect themselves from avoidable complications. An elderly woman with a mechanical heart valve was taking warfarin, a blood thinner to prevent and treat blood clots, when she began using the Chinese herb danshen, often marketed for “blood circulation”.