Menopause is a natural midlife change experienced by every women around 50 when the menstruation stops and the ovaries no longer produce eggs as the result of a reduction in female hormonal production. The transition from regular menstrual cycles to menopause takes a couple of years and typically is not a smooth process due to hormonal imbalance. Over the course, hot flashes, night sweats, mood swings, sleeplessness, lower back soreness, and other discomforts, which is called menopausal syndrome, may occur.

From the perspective of traditional Chinese medicine (TCM), menopause is the result of Kidney deficiency. The Kidneys are the primary source of Yin, Yang, and Jing (essence) of the body, whose function declines with the age. Hot flashes and the resulting restlessness are signs of Yin deficiency whereas soreness of the lower back is a sign of Kidney Jing deficiency. Although hot flashes are the most conspicuous sign of menopause, it can also be accompanied by cold feet, and sensitivity to cold temperatures. The alternating hot flashes and cold feet indicate the Kidney deficiency of both Yin and Yang energies. Er Xian Tang is a famous Chinese medicine uniquely formulated to supplement both Yin and Yang and may help women undergoing menopause smoothly manage their midlife challenge, especially when such signs of both Yin and Yang deficiency are manifested.

Er Xian Tang was invented in late 1950s in Shanghai and got its fame soon after. Er Xian Tang, literally "two immortals decoction", is named after its 2 major ingredients starting with Xian (immortal), Xian Mao and Xian Ling Pi, an alternative name for Yin Yang Huo or horny goat weed.

Er Xian Pian is a delicate combination of 6 Chinese herbs that warms Kidney Yang, tonifies Kidney Yin, nourishes Jing-essence, nourishes Liver Blood, drains Kidney Fire.^† In the formula, Xian Mao (Curculigo rhizome), Yin Yang Huo (Horny goat weed), and Ba Ji Tian (Morinda) as a group tonify the Kidney Yang, replenish the Kidney Jing, and strengthen the tendons and bones; Huang Bo (Phellodendron bark) and Zhi Mu (Anemarrhena) work as a pair to drain Kidney Fire, clear heat, and nourish Kidney Yin. Finally, Dang Gui (Angelica sinensis root) nourishes the blood and supports a healthy menstrual cycle.