Black cohosh: benefits, dosage & side-effects

Written by Madeleine Bailey on December 9, 2018 Reviewed by Dr Sarah Schenker on December 18, 2018 

Black cohosh, also known as Cimicifuga racemosa, is the root of a herb grown in the eastern United States and Canada. It was traditionally used by Native Americans for a range of complaints including: 

Today, black cohosh is mainly used to ease menopause symptoms, in particular:^2,3 

Black cohosh is available as capsules, tablets, tinctures and teas. 

Black cohosh is most well-known for its effect on menopausal symptoms. A 2010 York University review of studies on 1,400 menopausal women concluded that black cohosh reduced hot flushes and sweating by 25% compared with a placebo,⁴ while a study by Chinese researchers in 2015 suggested that black cohosh can help with menopausal sleep problems, leading to more time spent asleep.⁵ However, results have been mixed in other menopausal studies, so more research is needed.⁶ It’s not yet fully understood how black cohosh has this effect. In a 2008 study by the University of Missouri-Columbia, USA, scientists suggested that black cohosh may change how the neurotransmitter serotonin behaves in the body.⁷ Other theories are that the herb may act on the brain in the same way as the hormone oestrogen, or that black cohosh may have anti-inflammatory properties.⁸ 

Typically, 20–40mg of black cohosh extract has been used for studies into menopausal symptoms.⁹ Avoid taking it for more than six months: most black cohosh studies have stopped at six months, which means there’s a lack of research into its long-term safety. 

Studies have observed some serious side-effects, including liver damage, although this is rare and it’s not clear that black cohosh was responsible. However, if you experience any symptoms of liver damage – for example yellowing of the skin or eyes, nausea, vomiting and dark urine – you should stop taking the herb and see a doctor urgently.¹⁰ More common side-effects of taking black cohosh include: allergic skin rash upset stomach facial swelling headaches and dizziness low blood pressure changes in heart rhythm¹¹ Don’t take black cohosh if you: under 18 years of agehave or have had liver problems have or have had breast cancer – scientists are still not sure if black cohosh has an oestrogenic effect or not so it’s best to avoid it for now, just in case are child bearing age and do not use contraception are lactose intolerant are allergic to any of the ingredients are pregnant or breastfeeding – it has not been proven safe for these women¹²