There is no proven safe or effective dose for rhubarb. Furthermore, there is no consensus about doses using rhubarb, and there is a wide range of doses and preparations that have been studied or used. Traditionally, rhubarb has been taken as a decoction, tincture, tea, or powdered root for conditions such as constipation, diarrhea, or upset stomach in doses ranging from 0.1-4.0 grams per day. Enemas using 10 grams of rhubarb powder have also been used twice a day for up to seven days in chronic renal (kidney) failure patients.
Rhubarb is possibly safe when used short-term (less than 8 days) in lower doses. For upper gastrointestinal bleeding, 3 grams alcoholic extract tablets or powder or 6 milliliters of rhubarb syrup two to four times daily for up to two weeks have been used. For gonorrhea, 7-8 tablets of rhubarb (dose not specified) three times daily for four days have been used.
Rhubarb is often taken in large doses when using the crude material (root or stalk), and up to 50 grams of Rheum officinale decocted in 200 milliliters of liquid ingested once a day for 16 days has been used for hepatitis. For hypercholesterolemia (high cholesterol), 27 grams of ground rhubarb fiber stalk taken daily for four weeks has been used. Lower doses (6-9 grams of rhubarb daily for 6-22 months with an initial dose of 1 gram daily has been used; 0.5 gram daily with maximum doses of 3 grams daily for four weeks has been used; 1-3 grams of rhubarb extract daily for 6-48 months, with an average of 18.9 months has been used) have been studied in chronic renal failure patients.
For pre-eclampsia, 0.75 gram of rhubarb taken by mouth daily for 9-10 weeks, from the 28th week of pregnancy until delivery, has been used.
There is no proven safe or effective dose for rhubarb in children. According to traditional use, when rhubarb is used in older children or elderly over age 65, lower strength preparations should be used. In case reports, rhubarb has caused neonatal jaundice.
For the treatment of hepatitis, 25-30 grams of Rheum officinale decocted in 200 milliliters of liquid once a day for 16 days, with a one-day break every six treatments, has been used. For simple obesity, 5 tablets of 2.5-3.75 grams of refined rhubarb extract every night for one week has been used.