What is Black Cohosh?

Black Cohosh (Actaea racemosa, formerly Cimicifuga racemosa) is a perennial herb native to eastern North America. Its rhizome and root are the medicinally active parts, used for centuries by Indigenous North American peoples before adoption into Western herbalism and eventually commercial supplementation. It is one of the most widely studied botanical interventions for menopause and is approved by Germany's Commission E for climacteric (menopausal) complaints.

How does Black Cohosh work?

The precise mechanism remains incompletely characterized, but current evidence suggests Black Cohosh does not act as a classic phytoestrogen via direct estrogen receptor (ER-alpha) binding at typical doses. Instead, it appears to modulate serotonergic pathways—particularly 5-HT1A and 5-HT7 receptors—which may explain its effects on thermoregulation and mood. Some evidence points to selective ER-beta agonism and dopaminergic activity, along with central opioid receptor modulation, as contributing mechanisms.

What forms does Black Cohosh come in?

The most clinically studied form is a proprietary isopropanolic extract sold as Remifemin (standardized to triterpene glycosides). Most human clinical trials have used 40–80 mg of this standardized extract daily. Crude root preparations and tinctures are also commercially available but have less supporting clinical trial data specific to their standardization levels.

Where it comes from:

Indigenous peoples of eastern North America, including the Algonquin, Iroquois, and Cherokee, used Black Cohosh root medicinally for gynecological complaints, rheumatism, and as a general tonic. It entered mainstream Western botanical medicine in the 19th century and was listed in the US Pharmacopeia from 1820 to 1926. Modern clinical investigation began in Europe in the 1980s–1990s, with the proprietary Remifemin extract becoming the basis for most controlled research.

What does Black Cohosh help with?

Black cohosh is a flowering plant from North America. People have used its root as a medicine for hundreds of years. Most take it today for menopause symptoms.

• Hot flashes during and after menopause
  Good evidence — a review of 16 randomised human trials, plus single trials of a 40 mg daily extract. A 2012 review by Leach and Moore pooled 16 randomised trials. It ran in the Cochrane Database of Systematic Reviews. Hot flashes fell more than with placebo, but less than with hormone therapy. Single trials of Remifemin, a standard extract at 40 mg a day, found hot flash scores 25 to 50 percent lower in 8 to 12 weeks, on the Menopause Rating Scale and the Kupperman Index.
  Evidence grade B · Traditional tier T2
• Low mood, worry and short temper around menopause
  Good evidence — one 304-person randomised trial over 12 weeks, backed by lab receptor tests. Osmers and colleagues studied 304 women in 2005, in Obstetrics & Gynecology. The women took an isopropanol black cohosh extract for 12 weeks. Their mood scores on the Menopause Rating Scale beat placebo. In lab dish tests, plant compounds from the root bound to 5-HT1A, 5-HT7 and mu-opioid receptors, which are linked to mood.
  Evidence grade B · Traditional tier T2
• Night sweats
  Early evidence — night sweats tracked only inside hot flash trials; no trial made them the main outcome. Night sweats come from the same heat-control problem as hot flashes. In the menopause trials, night sweat scores fell along with the other hot flash scores. Those scores came from the Kupperman Menopausal Index and the Menopause Rating Scale. Lab work points to serotonin receptors, called 5-HT1A, in the brain's heat control area.
  Evidence grade C · Traditional tier T2
• Monthly PMS symptoms before a period
  Early evidence — one small 53-person randomised trial. Atmaca and colleagues tested black cohosh extract in 53 women in 2003. The report ran in Human Psychopharmacology. Women reported less irritability and less low mood. This work is early, and far weaker than the menopause research.
  Evidence grade C · Traditional tier T2
• Poor sleep during menopause
  Long traditional use · not yet tested in trials — sleep measured only as a side item on a symptom scale; no sleep-lab studies. Some trials tracked sleep as one item on the Menopause Rating Scale. Sleep scores improved when night sweat scores improved. No sleep-lab study, called polysomnography, has tested black cohosh. So any effect on sleep looks indirect.
  Evidence grade D · Traditional tier T2

What Black Cohosh has not been shown to do

• It has not been shown to match hormone therapy; in the pooled trials its effect on hot flashes was smaller.
• It has not been shown to work by switching on the classic estrogen receptors, so it is not a hormone replacement.
• It has not been shown to change sleep itself, apart from easing night sweats, because no sleep-lab study exists.
• It has not been shown to be a dependable choice for PMS; that evidence rests on one small trial and stays preliminary.

How to read this:

The grades describe the evidence, not a promise for you. A means many matching human trials. B means at least one good human trial. C means small or early human work. D means weak or mixed human data. Insufficient means no human study at all. This page lists options and findings. It is not medical advice. Black cohosh is not right for everyone, so talk with a clinician first.

What can Black Cohosh help prevent?

• Progression of menopausal vasomotor symptoms from moderate to severe (supported by symptom trajectory data from longer-term RCTs, though direct prevention trials are lacking)

What are the side effects of Black Cohosh?

• Gastrointestinal upset (nausea, stomach discomfort): most commonly reported side effect in clinical trials, typically mild
• Headache: reported in some RCT participants at higher frequencies than placebo
• Dizziness or lightheadedness: reported occasionally, possibly related to mild vasodilatory effects
• Rare hepatotoxicity: case reports of hepatitis, elevated liver enzymes, and in rare instances liver failure; mechanism unknown, possibly idiosyncratic
• Rash or skin reactions: uncommon allergic responses reported
• Weight gain: reported anecdotally but not consistently demonstrated in controlled trials
• Uterine stimulation: contraindicated in pregnancy due to historical use as an emmenagogue and theoretical risk of stimulating uterine contractions

Good to know:

Black Cohosh is generally well-tolerated at recommended doses (40–80 mg standardized extract daily) for periods up to 6 months, which is the duration covered by most clinical trials. The most significant safety concern is rare hepatotoxicity: over 50 spontaneous case reports of liver injury have been submitted to regulatory agencies worldwide (including the US, Europe, and Australia), leading to labeling requirements in multiple countries. Causality is not definitively established in all cases, but the signal is sufficient to warrant caution. The herb is contraindicated in those with existing liver disease and should be used with caution in anyone on hepatotoxic medications.

How much Black Cohosh should you take?

• Recommended daily: 40–80 mg/day of standardized isopropanolic or ethanolic root extract calibrated to 2.5% triterpene glycosides (equivalent to approximately 8–40 mg total triterpene glycosides). The most studied commercial dose is 40 mg once daily of Remifemin-equivalent extract. Crude root preparations: 300–600 mg dried root per day, though standardization is less reliable.
• Best time of day: No definitive evidence favoring a specific time of day; most clinical protocols administer once daily with the morning meal. If using a twice-daily split dose (e.g., 40 mg + 40 mg), one dose in the evening may help address nocturnal vasomotor symptoms.
• With or without food: Take with food to minimize gastrointestinal side effects (nausea is the most common complaint and is generally attenuated by food co-ingestion).
• Time to effect: Meaningful symptom reduction typically reported at 4–8 weeks; maximum benefit generally assessed at 8–12 weeks in clinical trials.
• How long to take it: Most clinical trials ran 8–24 weeks. The German Commission E and European Medicines Agency traditionally recommended limiting use to 6 months without medical supervision due to limited longer-term safety data, though some studies have extended to 12 months without new safety signals emerging. Periodic reassessment of continued need is advisable. Avoid use during pregnancy and lactation.