Drug & supplement interaction

Black Cohosh + Levothyroxine

Levothyroxine brand names: Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, and others.

No Known Interaction

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated July 2026 · Pair last verified Sep 13, 2026

The bottom line No known interaction

We found no known interaction between Black Cohosh and Levothyroxine in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the label for Levothyroxine states a food rule worth keeping to, and the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Black Cohosh and Levothyroxine

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Levothyroxine and Black Cohosh in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Black Cohosh safety at a glance

Black Cohosh overall Use caution Generally well tolerated short-term, but rare liver concerns mean medical guidance is wise.

Pregnancy Possibly Unsafe When used orally in pregnant patients who are not at term. Black cohosh might have hormonal effects and menstrual and uterine stimulant effects. Theoretically,... Read the full pregnancy detail

Breastfeeding Possibly Unsafe When used orally. Black cohosh might have hormonal effects. Theoretically, maternal intake of black cohosh might adversely affect a nursing child. Until more is... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Levothyroxine and Black Cohosh? Ask Dr. Brian Staiger, PharmD, BCPS directly ›

How we checked

Why No Interaction Is Listed for Levothyroxine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Levothyroxine is filed under 3 classifications — including thyroid hormone, oral drugs. Black Cohosh has documented interactions with 7 drug classes — the most serious being atorvastatin (lipitor) (moderate), cisplatin (platinol-aq) (moderate) and cytochrome p450 2d6 (cyp2d6) substrates (moderate) — and none of Levothyroxine’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Black Cohosh Does Interact With Other Medications

Black Cohosh has 636 moderate, 16 minor known drug interactions in our database — Levothyroxine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 636 Minor 16 No known interaction 2,178 (incl. Levothyroxine)

Taking anything else?

Check Another of Your Medications Against Black Cohosh

Covers the 2,830 medications we’ve checked against Black Cohosh. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Black Cohosh and Levothyroxine May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do. 2 of them are worth acting on rather than waiting out — marked below.

Seizures / Shortness of breath Worth acting on Additional detail
Black Cohosh
“There has been a case report of severe complications, including seizures, renal failure, and respiratory distress, in an infant whose mother was given an unknown dose of black cohosh and blue cohosh at 42 weeks gestation to induce labor. However, this adverse effect may have been attributable to blue cohosh.”

Black Cohosh · Natural Medicines adverse-effect record, reported in acute respiratory distress syndrome (ards).
3 sources cited

1122. McFarlin BL, Gibson MH, O'Rear J, Harman P. A national survey of herbal preparation use by nurse-midwives for labor stimulation. Review of the literature and recommendations for practice. J Nurse Midwifery 1999;44:205-16. PubMed

9492. Gunn TR, Wright IM. The use of black and blue cohosh in labour. N Z Med J 1996;109:410-1.

9493. Baillie N, Rasmussen P. Black and blue cohosh in labour. N Z Med J 1997;110:20-1.
“Orally, black cohosh may cause headache, dizziness, or tiredness. There is one case report of seizures in a female who used black cohosh, evening primrose oil, and chasteberry. A separate case report describes a 55-year-old female who experienced serotonin syndrome after the addition of black cohosh extract 40 mg daily to longstanding treatment with duloxetine 60 mg and sertraline 50 mg daily.

In one case, an infant…”

Black Cohosh · Natural Medicines adverse-effect record, reported in acute respiratory distress syndrome (ards).
6 sources cited

35852. Oktem M, Eroglu D, Karahan HB, Taskintuna N, Kuscu E, Zeyneloglu HB. Black cohosh and fluoxetine in the treatment of postmenopausal symptoms: a prospective, randomized trial. Adv Ther 2007;24:448-61. PubMed

35886. Wong, V. C., Lim, C. E., Luo, X., and Wong, W. S. Current alternative and complementary therapies used in menopause. Gynecol.Endocrinol. 2009;25(3):166-174. PubMed

10988. Huntley A, Ernst E. A systematic review of the safety of black cohosh. Menopause 2003;10:58-64.. DOI

116172. Dernbach MR, Carpenter JE, Shah N, Carter GB. Black Cohosh Interactions with Prescription Medications Associated with Serotonin Toxicity and Rhabdomyolysis: A Case Report. J Emerg Med 2024;66(5):e592-e596. PubMed

9492. Gunn TR, Wright IM. The use of black and blue cohosh in labour. N Z Med J 1996;109:410-1.

9493. Baillie N, Rasmussen P. Black and blue cohosh in labour. N Z Med J 1997;110:20-1.
Levothyroxine

Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›
Mood changes or irritability / A skin rash Additional detail

Black Cohosh

“Orally, black cohosh is generally well tolerated when used in typical doses.

Most Common Adverse Effects:

Orally: Breast tenderness, dizziness, gastrointestinal upset, headache, irritability, rash, tiredness.

Serious Adverse Effects (Rare):

Orally: Endometrial hyperplasia and hepatotoxicity, although data are conflicting for both.”

Black Cohosh · Natural Medicines adverse-effect record, reported in cluster headache.

Levothyroxine

Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›
Joint pain Additional detail
Black Cohosh
“One patient treated with black cohosh in a clinical trial discontinued treatment due to edema and arthralgia.

Black cohosh has been linked to asthenia, muscle damage, and rhabdomyolysis. In one case, a 54-year-old female experienced asthenia with elevated creatinine phosphokinase (CPK) and lactate dehydrogenase (LDH) levels while taking black cohosh.”

Black Cohosh · Natural Medicines adverse-effect record, reported in muscle breakdown.
3 sources cited

35897. Amsterdam JD, Yao Y, Mao JJ, Soeller I, Rockwell K, Shults J. Randomized, double-blind, placebo-controlled trial of Cimicifuga racemosa (black cohosh) in women with anxiety disorder due to menopause. J Clin Psychopharmacol 2009;29:478-83. PubMed

14299. Minciullo PL, Saija A, Patafi M, et al. Muscle damage induced by black cohosh (Cimicifuga racemosa). Phytomedicine 2006;13:115-8. PubMed

116172. Dernbach MR, Carpenter JE, Shah N, Carter GB. Black Cohosh Interactions with Prescription Medications Associated with Serotonin Toxicity and Rhabdomyolysis: A Case Report. J Emerg Med 2024;66(5):e592-e596. PubMed
Levothyroxine

Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›
Tiredness / Headache Additional detail

Black Cohosh

Recorded for Black Cohosh in the same Natural Medicines adverse-effect record shown under Mood changes or irritability / A skin rash above.

Levothyroxine

Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›

Reported for Black Cohosh but not commonly for Levothyroxine: liver problems, stomach upset, kidney problems and serotonin syndrome.

Effects for Levothyroxine come from the ADVERSE REACTIONS section of its FDA label; effects for Black Cohosh come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Black Cohosh in Pregnancy & Breastfeeding

Pregnancy Possibly Unsafe

When used orally in pregnant patients who are not at term. Black cohosh might have hormonal effects and menstrual and uterine stimulant effects. Theoretically, this might increase the risk of miscarriage; avoid using during pregnancy. There is insufficient reliable information available about the safety of black cohosh when used to induce labor.

Lactation Possibly Unsafe

When used orally. Black cohosh might have hormonal effects. Theoretically, maternal intake of black cohosh might adversely affect a nursing child. Until more is known, nursing patients should avoid taking black cohosh.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

How to take them

Some Levothyroxine Products Have a Food Rule — Black Cohosh Should Not Break It

At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach. Most supplements — Black Cohosh included — are taken with a meal, so the easy mistake is swallowing both together at breakfast. Where that rule applies, keep Levothyroxine on its own and move Black Cohosh to a meal later in the day.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Levothyroxine products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

From our Q&A

Questions About Black Cohosh or Levothyroxine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Black Cohosh or Levothyroxine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Levothyroxine

This page covers Black Cohosh only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levothyroxine page lists 50 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Tiratricol (major), Acetyl-l-carnitine (moderate), Alpha-lipoic Acid (moderate) and Ascophyllum Nodosum (moderate).

By severity: 2 major · 39 moderate · 9 minor.

From our pharmacist’s overview on the Levothyroxine page

“Levothyroxine replaces a hormone your body measures in tiny amounts, so small shifts in its blood level show up in how you feel, and I treat this list with genuine care. Nearly everything on it does one of two things: blocks the pill from being absorbed in the gut, the way everyday minerals like calcium do by binding it into complexes,…”

Reviewed by 2 · Jul 18, 2026

Open the Levothyroxine interaction page

One more smart check

Taking Black Cohosh as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,472 real supplement products containing Black Cohosh, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Cohosh. Even though Black Cohosh itself has no known interaction with Levothyroxine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Black Cohosh and Levothyroxine Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Black Cohosh

Top 25%

#155 of 1,452 supplements looked up here in the last 7 days

29 days ago today

Medication Levothyroxine

Top 10

#2 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?

Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Black Cohosh reference on this page ↓
Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Black Cohosh and Levothyroxine records this page draws on were last updated July 11, 2026.
What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.

Data structure & sourcing designed and verified by Dr. Brian Staiger, PharmD, BCPS.

Supplement

About Black Cohosh

What is Black Cohosh?

Hot flashes and night sweats
Other menopause symptoms
Mood changes during menopause
Premenstrual syndrome (PMS)
Menstrual cramps

Black cohosh is a North American plant most often used to ease menopause symptoms like hot flashes, but the research is mixed and far from settled. It is generally well tolerated for short-term use, though rare reports of liver problems mean you should talk with your pharmacist or doctor before trying it, especially if you have liver disease.

Actaea racemosa · Ranunculaceae · Roots and rhizomes (underground stems) · Capsules, tablets, liquid extracts (tinctures), dried root for tea

An interaction check asks whether these two react with each other — it does not ask whether Black Cohosh is a good idea for someone in your situation. Here is what our Black Cohosh record says about it on its own.

Black Cohosh: dosing

There is no official standard dose of black cohosh. Many supplements are standardized to their triterpene glycoside content, and studies have used a range of amounts, so products can differ a lot from one another.The safest approach is to follow the directions on the product label and not exceed the recommended amount.

From our Black Cohosh monograph — the full record covers uses, side effects and every documented interaction.

Read the full Black Cohosh monograph & all interactions

Medication

About Levothyroxine

What Is Levothyroxine Used For?

Brand names: Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, Levo-T, Eltroxin, Estre, Levothyroxine, Novothyrox, Levolet

Levothyroxine replaces or supplements the thyroid hormone your body isn't making enough of. It's used for hypothyroidism — an underactive thyroid — in adults, children, and even newborns, whether the cause is the thyroid gland itself, the pituitary gland, or the hypothalamus in the brain.

It's also used alongside surgery and radioiodine treatment in people with certain types of thyroid cancer, to help suppress the hormone that can stimulate cancer growth. It is not meant for weight loss, treating benign thyroid nodules in people who have enough iodine, or for hypothyroidism during recovery from a temporary condition called subacute thyroiditis.

See full Levothyroxine drug information

Keep checking

Other Drugs & Black Cohosh

Browse every other medication we’ve checked against Black Cohosh — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major

636Moderate

16Minor

2,177No known interaction

636 Moderate 16 Minor 2,177 No interaction

Moderate

636 interactions

Showing 60 of 636 moderate interactions — see all 636 on the Black Cohosh page.

Minor

16 interactions

No interaction 2,177 drugs checked — show the list

We also checked Black Cohosh against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,177 medications checked with no known interaction — see the full Black Cohosh list.

See the full Black Cohosh interactions page

See every supplement checked against Levothyroxine, ranked by severity

Evidence & sources

Black Cohosh References

The 68 references that drive our Black Cohosh monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

McFarlin BL, Gibson MH, O'Rear J, Harman P. A national survey of herbal preparation use by nurse-midwives for labor stimulation. Review of the literature and recommendations for practice. J Nurse Midwifery 1999;44:205-16. PubMed
Whiting PW, Clouston A, Kerlin P. Black cohosh and other herbal remedies associated with acute hepatitis. Med J Aust 2002;177:440-3. PubMed
Pepping J. Black cohosh: Cimicifuga racemosa. Am J Health Syst Pharm 1999;56:1400-2. PubMed
Liske E. Therapeutic efficacy and safety of Cimicifuga racemosa for gynecologic disorders. Adv Ther 1998;15:45-53.
Kruse SO, Lohning A, Pauli GF, et al. Fukiic and piscidic acid esters from the rhizome of Cimicifuga racemosa and the in vitro estrogenic activity of fukinolic acid. Planta Med 1999;65:763-4.
Jacobson JS, Troxel AB, Evans J, et al. Randomized trial of black cohosh for the treatment of hot flashes among women with a history of breast cancer. J Clin Oncol 2001;19:2739-45. PubMed
Gunn TR, Wright IM. The use of black and blue cohosh in labour. N Z Med J 1996;109:410-1.
Baillie N, Rasmussen P. Black and blue cohosh in labour. N Z Med J 1997;110:20-1.
Lontos S, Jones RM, Angus PW, Gow PJ. Acute liver failure associated with the use of herbal preparations containing black cohosh. Med J Aust 2003;179:390-1.. DOI
Wuttke W, Seidlova-Wuttke D, Gorkow C. The Cimicifuga preparation BNO 1055 vs. conjugated estrogens in a double-blind placebo-controlled study: effects on menopause symptoms and bone markers. Maturitas 2003;44:S67-77. PubMed
Huntley A, Ernst E. A systematic review of the safety of black cohosh. Menopause 2003;10:58-64.. DOI
Cohen SM, O'Connor AM, Hart J, et al. Autoimmune hepatitis associated with the use of black cohosh: a case study. Menopause 2004;11:575-7. PubMed
Vitetta L, Thomsen M, Sali A. Black cohosh and other herbal remedies associated with acute hepatitis. Med J Aust 2003;178:411-2.. PubMed
Thomsen M, Vitetta L, Schmidt M, Sali A. Acute liver failure associated with the use of herbal preparations containing black cohosh. Med J Aust 2004;180:598-600.. DOI
Cohen B, Schardt D. Center for Science in the Public Interest. Letter to Food and Drug Administration. Commissioner Mark McClellan, MD, PhD. March 4, 2004.
Seidlova-Wuttke D, Hesse O, Jarry H, et al. Evidence for selective estrogen receptor modulator activity in a black cohosh (Cimicifuga racemosa) extract: comparison with estradiol-17beta. Eur J Endocrinol 2003;149:351-62. PubMed
Rockwell S, Liu Y, Higgins SA. Alteration of the effects of cancer therapy agents on breast cancer cells by the herbal medicine black cohosh. Breast Cancer Res Treat 2005;90:233-9. PubMed
Levitsky J, Alli TA, Wisecarver J, Sorrell MF. Fulminant liver failure associated with the use of black cohosh. Dig Dis Sci 2005;50:538-9. PubMed
Cheong JL, Bucknall R. Retinal vein thrombosis associated with a herbal phytoestrogen preparation in a susceptible patient. Postgrad Med J 2005;81:266-7.. PubMed
Nappi RE, Malavasi B, Brundu B, Facchinetti F. Efficacy of Cimicifuga racemosa on climacteric complaints: a randomized study versus low-dose transdermal estradiol. Gynecol Endocrinol 2005;20:30-5.
Gurley BJ, Gardner SF, Hubbard MA, et al. In vivo effects of goldenseal, kava kava, black cohosh, and valerian on human cytochrome P450 1A2, 2D6, 2E1, and 3A4/5 phenotypes. Clin Pharmacol Ther 2005;77:415-26. PubMed
Minciullo PL, Saija A, Patafi M, et al. Muscle damage induced by black cohosh (Cimicifuga racemosa). Phytomedicine 2006;13:115-8. PubMed
Wuttke W, Gorkow C, Seidlova-Wuttke D. Effects of black cohosh (Cimicifuga racemosa) on bone turnover, vaginal mucosa, and various blood parameters in postmenopausal women: a double-blind, placebo-controlled, and conjugated estrogens-controlled study. Men PubMed
MHRA. Black cohosh (Cimicifuga racemosa) - risk of liver problems. Herbal Safety News July 2006. Available at: http://www.mhra.gov.uk/home/idcplg?IdcService=SS_GET_PAGE&useSecondary= true&ssDocName=CON2024131&ssTargetNodeId=663.
Dugoua JJ, Seely D, Perri D, et al. Safety and efficacy of black cohosh (cimicifuga racemosa) during pregnancy and lactation. Can J Clin Pharmacol 2006;13:e257-61.
Raus K, Brucker C, Gorkow C, Wuttke W. First-time proof of endometrial safety of the special black cohosh extract (Actaea or Cimicifuga racemosa extract) CR BNO 1055. Menopause 2006;13:678-91. PubMed
Lynch CR, Folkers ME, Hutson WR. Fulminant hepatic failure associated with the use of black cohosh: a case report. Liver Transpl 2006;12:989-92. PubMed
Bai W, Henneicke-von Zepelin HH, Wang S, et al. Efficacy and tolerability of a medicinal product containing an isopropanolic black cohosh extract in Chinese women with menopausal symptoms: A randomized, double blind, parallel-controlled study versus tibol
Meyer S, Vogt T, Obermann EC, et al. Cutaneous pseudolymphoma induced by Cimicifuga racemosa. Dermatology 2007;214:94-6.
Gori L, Firenzuoli F. Is black cohosh a hepatotoxic medicinal herb? Forsch Komplementarmed 2007;14:109-10. PubMed
Assessment of case reports connected to herbal medicinal products containing cimicifugae racemosa rhizoma (black cohosh, root). Doc. Ref. EMEA/269259/2006. Available at: www.emea.eu.int/pdfs/human/hmpc/26925806en.pdf (Accessed 30 November 2007).
Chung DJ, Kim HY, Park KH, et al. Black cohosh and St. John's wort (GYNO-Plus) for climacteric symptoms. Yonsei Med J 2007;48:289-94. PubMed
Chow ECY, Teo M, Ring JA, Chen JW. Liver failure associated with the use of black cohosh for menopausal symptoms. Med J Aust 2008;188:420-2. PubMed
Mahady GB, Low Dog T, Barrett ML, et al. United States Pharmacopeia review of the black cohosh case reports of hepatotoxicity. Menopause 2008;15:628-38. PubMed
Hepatotoxicity with black cohosh. Australian Adv Drug Reactions Bull 2006;25:6. Available at: www.tga.gov.au/adr/aadrb/aadr0604.htm#a1.
Dunbar K, Solga SF. Black cohosh, safety, and public awareness. Liver Int 2007;27:1017. PubMed
Patel NM, Derkits RM. Possible increase in liver enzymes secondary to atorvastatin and black cohosh administration. J Pharm Pract 2007;20:341-6. DOI
Joy D, Joy J, Duane P. Black cohosh: a cause of abnormal postmenopausal liver function tests. Climacteric 2008;11:84-8. PubMed
Australian Adverse Drug Reactions Advisory Committee. Black cohosh and liver toxicity - an update. Aust Adv Drug Reactions Bull 2007;26:11.
Gurley BJ, Swain A, Hubbard MA, et al. Clinical assessement of CYP2D6-mediated herb-drug interactions in humans: Effects of milk-thistle, black cohosh, goldenseal, kava kava, St. John's wort, and Echinacea. Mol Nutr Food Res 2008;52:755-63.
Spangler L, Newton KM, Grothaus LC, et al. The effects of black cohosh therapies on lipids, fibrinogen, glucose and insulin. Maturitas 2007;57:195-204. PubMed
Teschke R, Bahre R, Genthner A, et al. Suspected black cohosh hepatotoxicity - challenges and pitfalls of causality assessment. Maturitas 2009;63:302-14. PubMed
Brasky TM, Lampe JW, Potter JD, et al. Specialty supplements and breast cancer risk in the VITamins And Lifestyle (VITAL) cohort. Cancer Epidemiol Biomarkers Prev 2010;19:1696-708. PubMed
Fuchikami H, Satoh H, Tsujimoto M, Ohdo S, Ohtani H, Sawada Y. Effects of herbal extracts on the function of human organic anion-transporting polypeptide OATP-B. Drug Metab Dispos 2006;34:577-82. PubMed
Vermes G, Bánhidy F, Acs N. The effects of remifemin on subjective symptoms of menopause. Adv Ther 2005;22:148-54. PubMed
Nuntanakorn, P., Jiang, B., Einbond, L. S., Yang, H., Kronenberg, F., Weinstein, I. B., and Kennelly, E. J. Polyphenolic constituents of Actaea racemosa. J Nat Prod 2006;69(3):314-318.
Oktem M, Eroglu D, Karahan HB, Taskintuna N, Kuscu E, Zeyneloglu HB. Black cohosh and fluoxetine in the treatment of postmenopausal symptoms: a prospective, randomized trial. Adv Ther 2007;24:448-61. PubMed
Briese V, Stammwitz U, Friede M, Henneicke-von Zepelin HH. Black cohosh with or without St. John's wort for symptom-specific climacteric treatment--results of a large-scale, controlled, observational study. Maturitas 2007;57:405-14. PubMed
Naser, B. and Liske, E. Liver failure associated with the use of black cohosh for menopausal symptoms. Med J Aust. 1-19-2009;190(2):99. PubMed
van de Meerendonk, H. W., van Hunsel, F. P., and van der Wiel, H. E. [Autoimmune hepatitis induced by Actaea racemosa. Side affects of an herb extract]. Ned.Tijdschr.Geneeskd. 2-7-2009;153(6):246-249.
Wong, V. C., Lim, C. E., Luo, X., and Wong, W. S. Current alternative and complementary therapies used in menopause. Gynecol.Endocrinol. 2009;25(3):166-174. PubMed
Pierard, S., Coche, J. C., Lanthier, P., Dekoninck, X., Lanthier, N., Rahier, J., and Geubel, A. P. Severe hepatitis associated with the use of black cohosh: a report of two cases and an advice for caution. Eur J Gastroenterol Hepatol. 2009;21(8):941-945 PubMed
Vannacci, A., Lapi, F., Gallo, E., Vietri, M., Toti, M., Menniti-Ippolito, F., Raschetti, R., Firenzuoli, F., and Mugelli, A. A case of hepatitis associated with long-term use of Cimicifuga racemosa. Altern.Ther Health Med 2009;15(3):62-63.
Zimmermann, R., Witte, A., Voll, R. E., Strobel, J., and Frieser, M. Coagulation activation and fluid retention associated with the use of black cohosh: a case study. Climacteric. 2010;13(2):187-191. PubMed
Amsterdam JD, Yao Y, Mao JJ, Soeller I, Rockwell K, Shults J. Randomized, double-blind, placebo-controlled trial of Cimicifuga racemosa (black cohosh) in women with anxiety disorder due to menopause. J Clin Psychopharmacol 2009;29:478-83. PubMed
Bai WP, Wang SY, Liu JL, Geng L, Hu LN, Zhang ZL, Chen SL, Zheng SR. [Efficacy and safety of remifemin compared to tibolone for controlling of perimenopausal symptoms]. Zhonghua Fu Chan Ke Za Zhi 2009;44:597-600.
McKenzie, S. C. and Rahman, A. Bradycardia in a patient taking black cohosh. Med J Aust. 10-18-2010;193(8):479-481. PubMed
Stolze H. [An alternative to treat menopausal complaints]. Gynecologie 1982;1:14-16.
Guzman G, Kallwitz ER, Wojewoda C, et al. Liver Injury with Features Mimicking Autoimmune Hepatitis following the Use of Black Cohosh. Case Rep Med. 2009;2009:918156. PubMed
Enbom ET, Le MD, Oesterich L, Rutgers J, French SW. Mechanism of hepatotoxicity due to black cohosh (Cimicifuga racemosa): histological, immunohistochemical and electron microscopy analysis of two liver biopsies with clinical correlation. Exp Mol Pathol. PubMed
Sen A. Orobuccolingual dyskinesia after long-term use of black cohosh and ginseng. J Neuropsychiatry Clin Neurosci 2013 Fall;25(4):E50. PubMed
Hoban CL, Byard RW, Musgrave IF. Analysis of spontaneous adverse drug reactions to echinacea, valerian, black cohosh and ginkgo in Australia from 2000 to 2015. J Integr Med. 2019;17(5):338-343. PubMed
Pkhaladze L, Davidova N, Khomasuridze A, Shengelia R, Panossian AG. Actaea racemosa L. is more effective in combination with Rhodiola rosea L. for relief of menopausal symptoms: a randomized, double-blind, placebo-controlled study. Pharmaceuticals (Basel) PubMed
Yalçin M, Oguz A, Bestepe EE, Saglam NGU, Ergelen M. Black cohosh associated mania in a patient with unipolar depression. Int J Psychiatry Med 2020 Sep 21:91217420961185. doi: 10.1177/0091217420961185. PubMed
Brar HS, Marathi R. Case of cholestatic drug-induced liver injury (DILI) associated with black cohosh. BMJ Case Rep 2021;14(5):e240408. PubMed
Castelo-Branco C, Navarro C, Beltrán E, Losa F, Camacho M; on the behalf of the Natural Products Study Group of the Spanish Menopause Society. Black cohosh efficacy and safety for menopausal symptoms. The Spanish Menopause Society statement. Gynecol Endoc PubMed
Trant AA, Chagpar A, Wei W, et al. The Effect of Black Cohosh on Ki67 expression and Tumor Volume: A Pilot Study of Ductal Carcinoma in Situ Patients. Integr Cancer Ther 2022;21:15347354221137290. PubMed
Dernbach MR, Carpenter JE, Shah N, Carter GB. Black Cohosh Interactions with Prescription Medications Associated with Serotonin Toxicity and Rhabdomyolysis: A Case Report. J Emerg Med 2024;66(5):e592-e596. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Black Cohosh and Levothyroxine Together: Common Questions

Is it safe to take Black Cohosh with Levothyroxine?

We do not list a known interaction between Black Cohosh and Levothyroxine. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.

Do Black Cohosh and Levothyroxine have any of the same side effects?

Yes — our sources link each of them separately to 7 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.

Should I take Black Cohosh and Levothyroxine at the same time of day?

At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach, and supplements are usually taken with a meal — so taking them together at breakfast is the easy mistake. Where that applies, keep Levothyroxine on its own and move Black Cohosh to a meal later in the day. Food instructions belong to the product rather than the ingredient, so check the directions on your own box. This is about absorption, not an interaction.

How was the Black Cohosh and Levothyroxine combination checked?

Interactions in our licensed database are recorded against drug classes. Levothyroxine is filed under 3 classifications, and Black Cohosh has documented interactions with 7 drug classes — none of Levothyroxine's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.

Does Black Cohosh interact with any other medications?

Yes. Black Cohosh has 652 documented drug interactions in our database — Levothyroxine is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.

Does Levothyroxine interact with any supplements?

Yes. Levothyroxine has documented interactions with 50 supplements in our database — Black Cohosh is not one of them. The Levothyroxine interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Black Cohosh monograph Uses, safety profile, and every drug interaction in one place Levothyroxine drug information The full plain-English guide to this medication Levothyroxine supplement interactions Every supplement checked against Levothyroxine, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 68 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.