Red Clover
Summary
Red clover isoflavone extracts cut hot flashes by about 1.7 a day vs placebo in a 2021 meta-analysis, but results varied widely (grade C). Two US trials, at 82 mg and 120 mg/day of isoflavones, found no clinically important benefit (no effect). One 1-year trial found less spine bone loss (grade C).
Key facts
- Extract of Trifolium pratense flower tops, standardized to isoflavones (biochanin A, formononetin, genistein, daidzein)[1][3]
- Hot flashes: small pooled reduction (C) but null in the two largest US trials (no effect); lumbar spine bone loss slowed in one trial (C)[2][3][4][5]
- 37–160 mg/day of isoflavones (most often 40–80 mg) for 12 weeks to 2 years[2]
- None set; red clover is not a nutrient[1]
- None specific in our sources; NCCIH advises checking with a clinician if you take medicines[1]
- 4 graded human outcomes on this page
- October 10, 2026
How it works
ProposedRed clover isoflavones are plant compounds with weak estrogen-like activity, the proposed basis for effects on hot flashes and bone. A Cochrane review found no sign that phytoestrogen supplements stimulated the uterine lining or vagina over up to 2 years.[1][6]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Menopause | Grade C | Improved | Meta-analysis of 12 trials · n = 1,179 · 2021 | 3 rows |
| Bone | Grade C | Improved | RCT · n = 205 · 2004 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Daily hot flash frequency | Improved | Grade C | Meta-analysis · n = 1,179 · 2021 Perimenopausal and postmenopausal women in 12 RCTs (8 pooled for hot flash frequency) Form: red clover isoflavone extract · Dose: 37.1–160 mg/day isoflavones, mean 65.1 mg/day (aglycone equivalents) · Duration: 12 weeks to 2 years Hot flashes fell by 1.73 a day more than placebo (95% CI 0.18–3.28), with very high heterogeneity (87%). Effects were larger at 80 mg/day or more and in women with 5 or more flashes a day. | 33920485 (opens PubMed)Source [2] |
| Lumbar spine bone density | Improved | Grade C | RCT · n = 205 · 2004 UK women aged 49–65 Form: red clover isoflavone supplement · Dose: 26 mg biochanin A, 16 mg formononetin, 1 mg genistein and 0.5 mg daidzein per day (about 43.5 mg isoflavones) · Duration: 1 year Spine bone loss was smaller than with placebo (P = 0.03); hip bone density and bone-resorption markers did not change, and bone-formation markers rose. | 14749241 (opens PubMed)Source [5] |
| Hot flash frequency (ICE trial) | No effect | No effect | RCT · n = 252 · 2003 Recently postmenopausal US women with at least 35 hot flashes a week Form: two red clover isoflavone extracts · Dose: 82 mg/day (Promensil) or 57 mg/day (Rimostil) total isoflavones · Duration: 12 weeks Daily hot flashes fell by 5.1 and 5.4 with the extracts vs 5.0 with placebo. One extract worked faster, but neither had a clinically important effect. | 12851275 (opens PubMed)Source [3] |
| Vasomotor symptoms over 12 months | No effect | No effect | RCT · n = 89 · 2009 Perimenopausal and postmenopausal women in Chicago (four-arm trial) Form: ethanolic red clover extract · Dose: 398 mg/day extract standardized to 120 mg isoflavones · Duration: 12 months Vasomotor symptoms fell 57% with red clover vs 63% with placebo, not a significant difference; hormone therapy cut them 94%. Red clover was safe over 12 months. | 19609225 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Red clover isoflavone extract tablets (about 40–80 mg isoflavones) | Varies[2] | No human absorption data in our sources.[2] | Adverse events comparable to placebo in a 12-week trial.[3] | Hot flash trials |
| Ethanolic extract of aerial parts standardized to isoflavones | Varies[4] | No human absorption data in our sources.[4] | Safe over 12 months at 120 mg isoflavones/day.[4] | 12-month US hot flash trial (null) |
| Dried flower tops (tea) | Varies[1] | No human absorption data in our sources.[1] | No specific tolerance data in our sources.[1] | Traditional use; not tested in the trials on this page |
Studied doses
Doses studied in human trials ranged from 37 to 160 mg/day of red clover isoflavones, most often 40–80 mg/day, for 12 weeks to 2 years.[2]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Pregnancy and breastfeeding
- NCCIH says red clover supplements may be unsafe during pregnancy or breastfeeding.[1]
- Medicines
- No specific interactions are documented in our sources; NCCIH advises talking with a clinician before combining herbs with any medicine.[1]
- Expecting hormone-therapy results
- In a 12-month trial, hormone therapy cut vasomotor symptoms 94% while red clover did no better than placebo.[4]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Safety
Red clover extracts appeared safe in trials of up to 2 years.
- Tolerability
- Red clover extracts have been used in studies for as long as 2 years and appear well tolerated.[1]
- Uterine lining
- A Cochrane review found no evidence that phytoestrogen supplements stimulated the endometrium or vagina for up to 2 years.[6]
- Reporting gaps
- In the 2021 meta-analysis, 5 of 12 trials were at high risk of bias for not reporting adverse effects.[2]
How to read the label
- Label dose vs clinical doseTrials used 37–160 mg/day of isoflavones, most often 40–80 mg. Compare the isoflavone amount, not the weight of extract or flower.[2]
- Look for the isoflavone breakdownLabels that list biochanin A and formononetin let you compare with trials; pooled effects were larger with more biochanin A.[2][5]
- Extract weight is not isoflavone weightOne trial used 398 mg of extract to deliver 120 mg of isoflavones.[4]
Cost per studied dose, without the sales pitch
Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.
Cost per studied dose
Enter the price, servings and the amount per serving from your label.
Frequently asked questions
Does red clover help hot flashes?
Possibly a little. A 2021 meta-analysis found about 1.7 fewer hot flashes a day than placebo, but trials varied widely, and two US trials found no clinically important effect.[2][3][4]
How much red clover was studied?
Trials used 37–160 mg/day of isoflavones, most often 40–80 mg/day, for 12 weeks to 2 years.[2]
Is red clover as effective as hormone therapy?
No. In a 12-month trial, hormone therapy cut vasomotor symptoms 94%, while red clover (57%) did no better than placebo (63%).[4]
Does red clover help bones?
One 1-year UK trial found less spine bone loss but no effect at the hip. NCCIH calls the bone evidence limited and inconsistent.[1][5]
Is red clover safe?
Extracts have been used for up to 2 years in studies and appear well tolerated. NCCIH says it may be unsafe in pregnancy or breastfeeding.[1]
Sources
- [1]Red Clover: Usefulness and Safety (last updated April 2025). NIH National Center for Complementary and Integrative Health, 2025. fact-sheet
- [2]Evaluation of Clinical Meaningfulness of Red Clover (Trifolium pratense L.) Extract to Relieve Hot Flushes and Menopausal Symptoms in Peri- and Post-Menopausal Women: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.. Nutrients, 2021. meta-analysis
- [3]Phytoestrogen supplements for the treatment of hot flashes: the Isoflavone Clover Extract (ICE) Study: a randomized controlled trial.. JAMA, 2003. RCT
- [4]Safety and efficacy of black cohosh and red clover for the management of vasomotor symptoms: a randomized controlled trial.. Menopause, 2009. RCT
- [5]The effects of phytoestrogen isoflavones on bone density in women: a double-blind, randomized, placebo-controlled trial.. Am J Clin Nutr, 2004. RCT
- [6]Phytoestrogens for menopausal vasomotor symptoms.. Cochrane Database Syst Rev, 2013. systematic-review
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Adversarial review pass: every row re-read against its abstract and full text (PMC8069620 for the 1,179-woman total and dose range; PMC2783540 for the 398 mg / 120 mg red clover dose). The large null US trials were given their own rows so the pooled benefit is not overstated. Page set indexable.