Black cohosh for hot flashes: what the evidence says

Black cohosh has been tested in more randomized trials than any other herbal remedy for hot flashes, and the pooled result is that it does not beat placebo. It is generally well tolerated in trials lasting up to a year, but rare liver injury has been reported with products sold under its name, and the main US menopause and gynecology societies advise against recommending it.

What it is

Black cohosh (Actaea racemosa, formerly Cimicifuga racemosa) is a perennial in the buttercup family native to North America. Supplements are made from the root and rhizome and sold as powdered herb, liquid extracts, and dried extracts in tablets or capsules. Native Americans used it for musculoskeletal pain, fever and menstrual complaints; European settlers used it as a women’s tonic.

Which compounds, if any, are active is not known. Candidates include triterpene glycosides such as actein and 23-epi-26-deoxyactein, and aromatic acids. Because of that uncertainty, products vary widely in composition. Many are standardized to deliver at least 1 mg of triterpene glycosides per daily dose; one widely studied German extract is instead standardized to the equivalent of 40 mg of root per day. Black cohosh is not blue cohosh, a different plant with serious safety concerns.

Why women in midlife take it

Hot flashes and night sweats affect most women during the transition described in What is perimenopause?, and black cohosh is the best-known “natural” alternative to hormones. It is also marketed for sleep disturbance, irritability, palpitations and vaginal dryness.

What the evidence shows

The Cochrane review (2012). Leach and Moore identified 16 randomized controlled trials with 2,027 perimenopausal and postmenopausal women. All used oral single-ingredient black cohosh, at a median of 40 mg per day for a mean of 23 weeks, against placebo, hormone therapy, red clover or fluoxetine. Pooled across three trials (393 women), black cohosh changed hot flash frequency by 0.07 flashes per day relative to placebo, which is no difference. Menopausal symptom scores across four trials (357 women) also did not differ. Hormone therapy beat black cohosh on both. The authors concluded there is “insufficient evidence” to support its use, and noted that the trials were poorly reported.

The HALT trial (2006). This one-year US trial randomized 351 women aged 45 to 55 with two or more hot flashes a day to black cohosh 160 mg per day (a 70 percent ethanolic extract standardized to 2.5 percent triterpene glycosides), a multibotanical blend containing 200 mg of black cohosh plus nine other herbs, the blend plus soy counseling, estrogen with or without progestin, or placebo. At 3, 6 and 12 months, no herbal arm differed from placebo on hot flash frequency, intensity or a validated symptom scale. The difference between placebo and any herbal arm was always under one hot flash a day. Estrogen produced about four fewer hot flashes per day than placebo.

A second high-quality trial (2009). A 12-month trial in 88 women with at least 35 hot flashes a week compared black cohosh 128 mg per day (standardized to 5.7 percent triterpene glycosides), red clover, hormone therapy and placebo. Symptoms declined in every group, with no significant difference between black cohosh and placebo; at 6 and 9 months the black cohosh group had worse symptom intensity.

Meta-analysis (2016). In the JAMA review by Franco and colleagues, four black cohosh trials totaling 511 women at 6.5 to 160 mg per day showed no association with fewer hot flashes or better symptom scores.

A more favorable 2023 meta-analysis. NCCIH notes that a 2023 analysis found black cohosh “potentially beneficial” for overall menopause symptoms, with any benefit specific to hot flashes and none for anxiety or depression. This does not overturn the stronger individual trials, which were placebo-controlled, year-long and consistently null.

Guidelines. The 2023 Menopause Society statement lists supplements and herbal remedies as not recommended for hot flashes (Level I–II evidence). The Office of Dietary Supplements quotes ACOG’s conclusion that data “do not show” herbal supplements like black cohosh are effective for vasomotor symptoms.

Dose and form used in studies

Trials used 8 to 160 mg of extract per day, median 40 mg. Extracts were made with isopropyl alcohol or ethanol from root and rhizome, and many were standardized to a percentage of triterpene glycosides. Higher doses (128 to 160 mg) did not perform better than 40 mg. Because results were null across the range, there is no evidence-based dose.

Safety, interactions and who should avoid it

In trials, side effects were infrequent and mild: stomach upset and rash. Breast pain, spotting and musculoskeletal complaints occurred at similar rates on black cohosh and placebo. Most studies lasted six months or less; there are no long-term human safety data.

Separately, at least 83 case reports worldwide describe liver damage, including hepatitis and liver failure, in people taking products labeled as black cohosh. Causation has not been established, and some cases may involve adulteration, contaminants or the wrong Actaea species, though the products were not independently analyzed. Australia has required a liver warning since 2007. In 2008 the US Pharmacopeia recommended a cautionary label (“Discontinue use and consult a healthcare practitioner if you have a liver disorder or develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice”). The FDA does not require it.

Who should avoid it: anyone with liver disease; pregnant women, unless under supervision, because safety has not been studied; and, pending more data, women with hormone-sensitive conditions, since the herb’s effect on estrogen is unresolved.

Interactions: none clinically relevant are known, but this has not been systematically studied. That applies to hormone therapy, SSRIs and SNRIs, thyroid medication and anticoagulants alike. Tell your prescriber and pharmacist.

How to choose a product, if you try it

Choose a single-ingredient product, not a “menopause blend,” so the dose is visible. Check that the Supplement Facts panel names the plant part (root and rhizome) and the extract amount in milligrams. Prefer a product with a third-party certification mark, which addresses the identity and adulteration problems behind the liver case reports; see our guide to third-party testing. Set an 8 to 12 week trial, log symptoms with the symptom check, and stop if nothing changes or if you notice abdominal pain, dark urine or jaundice.

Bottom line

Black cohosh is well tolerated in the short term, but the best trials show it does not reduce hot flashes more than placebo, and liver safety is an open question. If hot flashes are disrupting your life, effective options exist, both hormonal and nonhormonal. A clinician who treats menopause regularly can match one to your history; see how to find a menopause specialist or search the clinician finder.