Barberry is most commonly used traditionally for gastrointestinal (GI) tract discomforts such as heartburn, stomach cramps, constipation, and lack of appetite.
 
Caution and Side Effects of Barberry:
Pregnancy and breast-feeding: Don't use Barberry by mouth if you are pregnant or breast-feeding. It is LIKELY UNSAFE for your baby. The berberine in Barberry can pass from a mother's body into her unborn child through the placenta. Brain damage has developed in newborns exposed to berberine. Similarly, berberine, as well as other harmful chemicals in Barberry, can be transferred to an infant through breast milk, and might cause brain damage.Bleeding disorder: Barberry contains a chemical called berberine. Berberine might slow blood clotting and increase the risk of bleeding. In theory, Barberry might make bleeding disorders worse.
Diabetes: Barberry contains a chemical called berberine. Berberine might lower blood sugar levels. Watch for signs of low blood sugar (hypoglycemia) and monitor your blood sugar carefully if you have diabetes and use Barberry in amounts larger than the amounts normally found in food.