*It should be noted that rhubarb, while tart and nutritious, is toxic to humans if the top leaves are consumed (only eat the red stalks, or petioles)
*Pregnant and nursing women should not use Chinese Rhubarb Root Herbal Supplement (it is a uterine stimulant)
* It should not be used by those who suffer from colitis or have intestinal obstruction
* Kidney stones : Rhubarb is high in calcium, more than a comparable cup of milk. Unfortunately, the calcium is in the form of calcium oxalate, which blocks absorption of calcium not only from the ingested rhubarb itself, but also from any other food eaten at the same time. Cooking converts the oxalic acid into an inorganic crystalline form which can build up into kidney stones. Those who tend to develop kidney stones with oxalate content should avoid rhubarb.
* Diarrhea or constipation: Rhubarb can make diarrhea or constipation worse, depending on the preparation used.