Dong Quai has been used for PMS and menstrual pain for years, although there is little to no data about it. I've not heard about it being used for "heavy period" per se.
Before taking like Dong Quai or any herbal supplement, it is good to check out potential interactions with medication you are taking. If you are taking a beta blocker or calcium channel blocker for your high blood pressure, it can increase the effect of the drug. It also has been used in China for high blood pressure, so it may indeed increase the action of any antihypertensive you are taking.
Talk with your trusted health care practitioner about this before trying it. A heavy period by itself is inconvenient, but not necessarily a problem if you are not anemic.
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