Black Cohosh Side Effects: What to Know

Overview

Black cohosh is generally well-tolerated for short-term use, but significant safety concerns exist regarding liver toxicity. While liver damage is rare, it has prompted FDA warnings and recommendations to limit use to 6 months or less. Common side effects include gastrointestinal upset and headache.

Common Side Effects

Gastrointestinal

• Stomach upset
• Nausea
• Diarrhea
• Abdominal discomfort

Prevention: Take with food to minimize GI effects.

Neurological

• Headache (common)
• Dizziness

Other Common Effects

• Weight gain (some reports)
• Rash
• Breast tenderness (uncommon)

Liver Safety — Important Warning

FDA Warning

The FDA has warned about potential liver toxicity:

• Rare but serious cases of liver damage reported
• Some cases required liver transplant
• At least one death attributed to black cohosh
• Mechanism not clearly understood

Signs of Liver Problems

Stop immediately and seek medical care if:

• Yellowing of skin or eyes (jaundice)
• Dark urine
• Light-colored stools
• Unusual fatigue
• Upper right abdominal pain
• Nausea with loss of appetite
• Unexplained itching

Risk Factors

• Pre-existing liver disease
• Concurrent use of liver-affecting medications
• Alcohol use
• Prolonged use (>6 months)

Precautions

• Limit use to 6 months or less
• Do not use if you have liver disease
• Monitor for symptoms
• Consider periodic liver function tests for extended use

Serious Side Effects (Rare)

Liver Damage

• Case reports of hepatitis
• Some cases of liver failure
• Rare but potentially severe
• Reversible if caught early and stopped

Allergic Reactions

• Skin rash
• Itching
• Swelling
• Difficulty breathing (severe—emergency)

Cardiovascular (Theoretical)

• Rare reports of low blood pressure
• Slowed heart rate
• Generally not clinically significant

Hormonal Considerations

Estrogen-Like Effects?

Current evidence suggests:

• Black cohosh does NOT act as a phytoestrogen
• Does not appear to stimulate estrogen receptors
• Generally considered safe for breast cancer survivors
• However, some precautionary warnings remain

Implications

• May be option for women avoiding estrogens
• Breast cancer organizations generally allow its use
• Discuss with oncologist if history of hormone-sensitive cancer

Drug Interactions

Medications Processed by Liver

• May affect CYP450 enzyme system
• Could alter metabolism of many medications
• Examples: statins, some antidepressants, warfarin

Specific Interactions

Use with caution:

• Hepatotoxic medications (statins, acetaminophen)
• Chemotherapy drugs
• Medications for hormone-sensitive conditions
• Blood thinners

Before Surgery

• Stop 2 weeks before
• May affect anesthesia metabolism
• Inform surgical team

Who Should Avoid Black Cohosh

Absolute Contraindications

• Liver disease or history of liver problems
• Active hepatitis
• Known allergy to black cohosh

Relative Contraindications

• Heavy alcohol use
• Taking hepatotoxic medications
• Multiple medications processed by liver

Precautionary Avoidance

• Pregnancy (safety unknown)
• Breastfeeding (safety unknown)
• Hormone-sensitive cancers (discuss with oncologist)

Long-Term Safety

Duration Concerns

• Long-term safety not established
• Liver effects may be cumulative
• Recommend limiting to 6 months

Monitoring for Extended Use

• Consider liver function tests
• Regular symptom assessment
• Periodic breaks from use

Comparison to Hormone Therapy

Black Cohosh Side Effects

• Liver concerns unique to black cohosh
• Generally milder overall profile
• No blood clot risk
• No cardiovascular concerns

Hormone Therapy Side Effects

• Blood clot risk
• Cardiovascular considerations
• Breast tenderness
• Uterine bleeding
• More effective but more side effects

If Side Effects Occur

Mild GI Symptoms

• Try taking with food
• Reduce dose if tolerable
• Usually resolve with continued use

Liver Symptoms

• Stop immediately
• Seek medical evaluation
• May need liver function tests

Allergic Symptoms

• Stop use
• Seek medical care for severe reactions

Reporting Side Effects

• Report serious effects to FDA MedWatch
• Inform healthcare providers
• Help improve safety data

Sources

• National Institutes of Health, Office of Dietary Supplements. Black Cohosh: Fact Sheet for Health Professionals. Last updated October 2020. https://ods.od.nih.gov/factsheets/BlackCohosh-HealthProfessional/. Accessed March 2026.
• National Institutes of Health, Office of Dietary Supplements. Black Cohosh: Fact Sheet for Consumers. Last updated October 2020. https://ods.od.nih.gov/factsheets/BlackCohosh-Consumer/. Accessed March 2026.
• MedlinePlus. Black cohosh. Natural product information. https://medlineplus.gov/druginfo/natural/953.html. Accessed March 2026.