Used internally and externally for a wide range of conditions. Yarrow is a remedy that operates on blood vessels, especially the smaller arteries and veins, and has an effect on blood constituents as well. In practice it works most especially on the digestive tract, pelvic organs, and peripheral circulation. It is also used for temperature reduction in the early stages of fevers, flu, and the common cold. It is usually taken as a tincture or a tea. Yarrow should not be used by pregnant women or by people who are taking warfarin or heparin.