The usual dosage of Radix Rehmanniae Praeparata decoction is 9-15 grams per day, or as directed by the doctor.
Radix Rehmanniae Praeparata has the effect of tonifying blood and nourishing yin, benefiting the essence and filling in the marrow. It is used in treating blood deficiency, palpitations (rapid heartbeat, often accompanied by panic), irregular menstruation, metrorrhagia (excessive menstrual flow or dribbling), hemorrhage, yin deficiency of liver and kidney (insufficient yin in the liver and kidneys), lumbar and knee soreness (a feeling of soreness and weakness in the lumbar and knee areas), spermatorrhea, internal heatiness and thirstiness (heatiness accompanied by excessive eating, drinking, urinating, and so forth), dizziness, ringing in the ears, and premature graying of the whiskers and hair.
Because of its warm nature, it is not suitable to be taken in large quantities for a long period of time for those who are suffering from external warmth and internal heat; it is also not suitable to be taken in large quantities for a long period of time for those who are suffering from stagnation of qi and phlegm, abdominal distension, and loose stools (sparse and unshapely feces).
It is recommended to use medication under the guidance of a doctor after identifying the symptoms.