Milk thistle is likely safe when taken by mouth for most adults. Milk thistle sometimes causes a laxative effect. Other less common side effects are nausea, diarrhea, indigestion, intestinal gas, bloating, fullness or pain and loss of appetite.
Special Precautions & Warnings:
Pregnancy and breast-feeding: Not enough is known about the use of milk thistle during pregnancy and breast-feeding. Stay on the safe side and avoid use.
Allergy to ragweed and related plants: Milk thistle may cause an allergic reaction in people who are sensitive to the Asteraceae/Compositae plant family. Members of this family include ragweed, chrysanthemums, marigolds, daisies, and many others. If you have allergies, be sure to check with your healthcare provider before taking milk thistle.
Diabetes: Certain chemicals in milk thistle might lower blood sugar in people with diabetes. Dosing adjustments to diabetes medications might be necessary.
Hormone-sensitive conditions such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Extracts from milk thistle plant might act like estrogen. If you have any condition that might be made worse by exposure to estrogen, donot use these extracts. In contrast, the more commonly used milk thistle seeds extracts do not seem to act like estrogen.