Black cohosh should not be used by pregnant or breast-feeding women.¹⁷ Very large amounts (over a few grams daily) of this herb may cause abdominal pain, nausea, headaches, and dizziness.

There is one case report of a woman developing autoimmune hepatitis while using black cohosh.¹⁸ A cause–effect relationship is in doubt, however, because the hepatitis did not resolve after black cohosh was discontinued. A few cases have also been reported in which severe liver failure was attributed to the use of black cohosh.¹⁹ While a cause–effect relationship is difficult to prove, and while such a side effect appears to be rare, people taking black cohosh should be alert to signs of possible liver disease, such as nausea, loss of appetite, fatigue, and tan-coloured urine. Black cohosh is not a substitute for hormone replacement therapy during menopause.