Red clover

What it is

Red clover is a legume of the Fabaceae family grown mainly as a forage crop, whose flowering tops are extracted to make menopause supplements. Its active constituents are isoflavones, phenolic compounds with a chemical structure similar to that of estradiol, chiefly biochanin A and formononetin. Isoflavone content in red clover is high compared with soy, in the range of 10 to 25 mg per gram of dry weight. Commercial products are standardised, when they are standardised at all, to isoflavone or aglycone isoflavone equivalents.

What the research says

Red clover is sold for hot flushes and other menopausal symptoms, and this is where the evidence is both strongest and most contested. One meta-analysis of eight trials found about 1.7 fewer hot flushes a day than placebo, but with very high heterogeneity; another meta-analysis of eleven trials found a difference that did not reach statistical significance, and NCCIH's position is that the research has not shown conclusive evidence of benefit for any condition. A pooled analysis found a small drop in total cholesterol and a small rise in HDL. Human trials have not shown clinically meaningful effects on clotting, but a case report describes a bleeding disorder after misuse, and the bigger documented problem is product quality: commercial red clover products vary enormously in content and have been found contaminated with heavy metals and, in at least one analysis, with warfarin.

Evidence grade: Disputed.

What goes wrong

In the larger of those trials adverse effects were reported and were distributed equally between red clover and placebo, most commonly breast abnormality and unspecified skin symptoms. (Source 1)

• Randomized trial, Low certainty.
• Size: 401 women.
• Who: women with at least one first degree relative affected by breast cancer.
• How long: not stated in the review.
• Result: no rates given; most common were breast abnormality and skin related symptoms, equally distributed between arms; the other trial did not report adverse events.
• Funding: Canadian Institutes of Health Research Knowledge Synthesis grant.

Atkinson did not report adverse events. Powles reported adverse effects, which most commonly included breast abnormality, "skin related symptoms" (not described), and other minor adverse events, however these were equally distributed between red clover and placebo groups.

A case report describes a bleeding disorder in a young woman after misuse of red clover. (Source 2)

• Case report, Very low certainty.
• Size: 1 patient.
• Who: a 28-year-old woman taking red clover.
• How long: not reported in the abstract.
• Result: a coagulation disorder; the abstract available to us did not give the laboratory values.
• Funding: not stated.

Here a case of bleeding disorder in a 28-year-old woman taking red clover is reported.

A review of red clover product quality found wide variation in isoflavone content between commercial products, including a 385-fold range in one constituent. (Source 3)

• Systematic review, Very low certainty.
• Size: more than 30 human clinical trials and systematic reviews identified; product analyses summarised from primary studies.
• Who: commercial Trifolium pratense products.
• How long: publications from 2000 to 2025.
• Result: formononetin content varied 385-fold and biochanin A varied 45-fold; other analyses found actual isoflavone contents from 87 to 107% of label claims.
• Funding: not stated.

formononetin content varied 385-fold and biochanin A varied 45-fold; products also exhibited greater chromatographic impurities

The same review reports heavy metal contamination of red clover supplements exceeding pharmacopoeial limits in about a third of products tested, and one analysis found warfarin contamination. (Source 3)

• Systematic review, Very low certainty.
• Size: not stated in the extract; contamination figures drawn from product-testing studies.
• Who: commercial red clover supplements.
• How long: not applicable.
• Result: 30.51% exceeded pharmacopoeial limits for at least one heavy metal (cadmium, lead, arsenic, mercury or copper); cadmium and lead detected in 68% and mercury in 29% of supplements tested; warfarin contamination found in one analysis.
• Funding: not stated.

30.51% exceeded pharmacopoeial limits for at least one heavy metal cadmium, lead, arsenic, mercury, or copper

That review attributes the rare serious adverse events reported for red clover to adulteration rather than to the plant itself. (Source 3)

• Systematic review, Very low certainty.
• Size: more than 30 human clinical trials and systematic reviews.
• Who: peri- and postmenopausal women.
• How long: 8 weeks to 3 years.
• Result: no rates given for the adulteration-linked events.
• Funding: not stated.

Rare adverse events were primarily linked to adulteration rather than intrinsic toxicity.

NCCIH also states red clover supplements may be unsafe in pregnancy and breastfeeding, while extracts used in trials for up to two years appeared well tolerated. (Source 4)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: pregnant and breastfeeding women; clinical trial participants.
• How long: clinical studies of up to 2 years.
• Result: no rates given.
• Funding: US government agency.

Red clover supplements may be unsafe for use during pregnancy or while breastfeeding.

What the evidence supports

A meta-analysis of eight randomised trials found red clover reduced daily hot flushes compared with placebo, but with very high statistical heterogeneity between trials. (Source 5)

• Meta-analysis, Low certainty.
• Size: eight trials, ten comparisons.
• Who: peri- and post-menopausal women.
• How long: varied between trials; not pooled in the abstract.
• Result: WMD −1.73 hot flushes per day (95% CI −3.28 to −0.18; p = 0.0292); I² 87.34%.
• Funding: This research received no external funding.

A meta-analysis of eight trials (ten comparisons) demonstrated a statistically significant reduction in the daily incidence of hot flushes in women receiving red clover compared to those receiving placebo: weighted mean difference (WMD—weighted mean difference) −1.73 hot flushes per day, 95% CI (confidence interval) −3.28 to −0.18; p = 0.0292.

Neither of the two randomised trials of red clover in women at higher breast cancer risk found changes in mammographic density, and one found no change in endometrial thickness. (Source 1)

• Systematic review, Low certainty.
• Size: two RCTs, 205 and 401 women.
• Who: women with dense breast patterns, and women with a family history of breast cancer.
• How long: not stated in the review.
• Result: no significant changes in mammographic density in pre- or post-menopausal women; no significant change in endometrial thickness between groups.
• Funding: Canadian Institutes of Health Research Knowledge Synthesis grant; funders had no role.

Neither of the two RCTs reported any significant changes in mammographic density among both pre- and post-menopausal women, and Powles found no significant changes in endometrial thickness between groups.

EFSA's 2015 risk assessment concluded that no adverse effects on the uterus were noted for red clover extract in post-menopausal women at the doses and durations it reviewed. (Source 6)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: post-menopausal women without a current diagnosis or history of oestrogen-dependent breast or uterine cancer.
• How long: the doses and durations reviewed in the opinion.
• Result: no adverse uterine effects identified; no single safe intake level could be derived.
• Funding: European Union agency.

no adverse effects on the uterus were noted for soy isoflavones/soy extract, soy protein, daidzein-rich isoflavones, glycitein-rich isoflavones, genistein and red clover extract in post-menopausal women when taken in doses and for durations as described

What the evidence does not support

A separate meta-analysis of eleven randomised trials found the reduction in hot flush frequency with red clover was not statistically significant. (Source 7)

• Meta-analysis, Very low certainty.
• Size: 11 RCTs, selected from 183 relevant publication trials.
• Who: menopausal women.
• How long: varied; not pooled.
• Result: mean difference in hot flash frequency −1.99, p=0.067 (not statistically significant)
• Funding: not stated.

The mean hot flashes frequency in red clover was lower than the control groups (MD -1.99; p=0.067).

In a randomised trial in 205 women at increased breast cancer risk, red clover did not change hot flush score or the number of daily hot flushes. (Source 1)

• Randomized trial, Moderate certainty.
• Size: 205 women.
• Who: women with increased breast cancer risk from Wolfe P2 or DY mammographic breast patterns.
• How long: not stated in the review.
• Result: no significant change in hot flash score (p=0.88) or mean number of daily hot flashes (p=0.41)
• Funding: the review itself was funded by a Knowledge Synthesis grant from the Canadian Institutes of Health Research.

Results of the study by Atkinson showed no significant changes in hot flash score (p=0.88) or mean number of daily hot flashes (p=0.41) when groups were compared.

A six-month randomised study of red clover plus soy isoflavones in 150 postmenopausal women found no significant change in clotting measures. (Source 3)

• Randomized trial, Low certainty.
• Size: 150 postmenopausal women.
• Who: postmenopausal women.
• How long: six months.
• Result: no significant changes in PT, aPTT, fibrinogen or antithrombin III (p > 0.05) on 60.8 mg/day red clover isoflavones plus 19.2 mg/day soy isoflavones.
• Funding: not stated.

A randomized study of 150 postmenopausal women receiving 60.8 mg/day T. pratense isoflavones plus 19.2 mg/day soy isoflavones (total 80 mg/day) for six months found no significant changes in PT, aPTT, fibrinogen, or antithrombin III (p > 0.05) (Mainini et al., 2013).

NCCIH's position, as of April 2025, is that red clover research has not produced conclusive evidence of benefit for any health condition and that hot flush results have been inconsistent with some trials at high risk of bias. (Source 4)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: general public.
• How long: not applicable.
• Result: no numbers given; a qualitative agency summary.
• Funding: US government agency.

Studies on the effects of red clover on hot flashes associated with menopause have had inconsistent results, and some of the studies had a high risk of bias.

Where the evidence is mixed

The authors of that meta-analysis warned that their own positive reading was undermined by flaws in the included trials and large heterogeneity. (Source 7)

• Meta-analysis, Very low certainty.
• Size: 11 RCTs.
• Who: menopausal women.
• How long: varied.
• Result: no revised estimate given; a qualitative caveat on the pooled result.
• Funding: not stated.

However, the interpretation of results of the current study is limited due to methodological flaws of the included studies, menopause status, and large heterogeneity among them.

A meta-analysis of phytoestrogen trials in postmenopausal women found a small reduction in total cholesterol and a small rise in HDL cholesterol with red clover, and no change in LDL. (Source 8)

• Meta-analysis, Low certainty.
• Size: 42 randomised controlled trials across flaxseed, soy and red clover.
• Who: postmenopausal women.
• How long: varied; not pooled in the abstract.
• Result: total cholesterol WMD −0.11 (95% CI −0.18 to −0.04; p = 0.0017); HDL-C WMD 0.04 (95% CI 0.01 to 0.07; p = 0.0165); LDL-C WMD −0.01 (95% CI −0.13 to 0.10; p = 0.8230)
• Funding: not stated in the accessible content.

There was a significant reduction in TC levels after the use of red clover (WMD = −0.11; 95% CI: −0.18–−0.04; p = 0.0017) and a statistically significant increase in HDL-C levels (WMD = 0.04; 95% CI: 0.01 to 0.07; p = 0.0165).

Where the research disagrees

Whether red clover reduces hot flushes

• Authors of the 2021 Nutrients meta-analysis of eight trials, meta-analysis of randomised controlled trials, I² 87.34%: weighted mean difference (WMD—weighted mean difference) −1.73 hot flushes per day, 95% CI (confidence interval) −3.28 to −0.18; p = 0.0292 (Source 5)
• Authors of the 11-trial meta-analysis in Avicenna Journal of Phytomedicine, meta-analysis of randomised controlled trials, result not statistically significant: The mean hot flashes frequency in red clover was lower than the control groups (MD -1.99; p=0.067). (Source 7)
• NCCIH, April 2025, agency position: Red clover has been studied in people, but the research hasn't shown conclusive evidence of benefits for any health condition. (Source 4)

Whether red clover affects blood clotting

• Authors of a 2018 case report in Frontiers in Emergency Medicine, single case report: Here a case of bleeding disorder in a 28-year-old woman taking red clover is reported. (Source 2)
• Authors of a 2026 review of red clover safety, review of human randomised trials: Evidence from human trials shows that T. pratense does not exert clinically meaningful anticoagulant or antiplatelet effects at standard supplemental doses (Nestel et al., 1999; Teede et al., 2003; Wickham et al., 2022). (Source 3)

How much

• Reference intake: No reference intake exists for red clover isoflavones. EFSA's 2015 opinion states that a single health-based guidance value or safe intake level for isoflavone supplements could not be derived. (Source 6)
• Upper limit: No numerical upper limit or ADI has been set. A 2026 review records that the South African regulator instead applies product-quality requirements and contraindications, including pregnancy, breastfeeding and concurrent use of estrogens or anticoagulants such as warfarin (SAHPRA, 2022). (Source 3)
• Studied: Across eight randomised trials pooled in 2021, the average red clover isoflavone dose was 65.1 mg/day of aglycone equivalent, with a range of 37.1 to 160 mg/day. (Source 5)
• Studied: 80 mg/day of standardised isoflavones was the dose at which vasomotor symptom benefits were most consistent in the trials summarised in a 2026 review; a 12-week trial used 150 mL/day of extract providing 37.1 mg isoflavones. (Source 3)
• Studied: 60.8 mg/day of red clover isoflavones plus 19.2 mg/day of soy isoflavones for six months in a clotting study of 150 postmenopausal women. (Source 3)

A common belief, and what the research shows

The belief: Red clover is a gentle, natural alternative to hormone therapy, so it is inherently safe and reliably effective.

What the research shows: Neither half of that holds up. On effectiveness, the pooled trials disagree with each other: one meta-analysis found "weighted mean difference (WMD—weighted mean difference) −1.73 hot flushes per day, 95% CI (confidence interval) −3.28 to −0.18; p = 0.0292" while another found "The mean hot flashes frequency in red clover was lower than the control groups (MD -1.99; p=0.067).", and NCCIH's position is that "Red clover has been studied in people, but the research hasn't shown conclusive evidence of benefits for any health condition." On safety, the documented problem is what is in the bottle: a 2026 review found that "formononetin content varied 385-fold and biochanin A varied 45-fold; products also exhibited greater chromatographic impurities", that "30.51% exceeded pharmacopoeial limits for at least one heavy metal cadmium, lead, arsenic, mercury, or copper", and that "Rare adverse events were primarily linked to adulteration rather than intrinsic toxicity."

Questions and answers

What is it?

Red clover is a legume, Trifolium pratense, in the same plant family as soy, white clover, alfalfa and beans. Supplements are made from its flowering tops. The constituents of interest are isoflavones, and red clover is a particularly concentrated source of them. (Source 9)

What does it do in the body?

Red clover's isoflavones are phenolic compounds whose shape resembles the human oestrogen estradiol, which is why they are called phytoestrogens and why they are studied for menopausal symptoms. In post-menopausal women, EFSA's review of the evidence found no adverse effects on the uterus from red clover extract at the doses and durations assessed, so the oestrogen-like resemblance does not translate into oestrogen-like tissue effects at those intakes. (Source 9)

Is it good or bad for you?

It depends on which result you trust and on the product. Pooled trials are split on hot flushes, and NCCIH's position is that no benefit has been conclusively shown for any condition. Extracts used in trials for up to two years appeared well tolerated, but supplements may be unsafe in pregnancy and breastfeeding, and product-testing studies have found heavy metal contamination and even warfarin in commercial products. (Source 4)

How do you get more of it?

Red clover is taken as a standardised isoflavone extract rather than eaten. Across eight pooled randomised trials the average dose was 65.1 mg a day of aglycone equivalent, ranging from 37.1 to 160 mg a day. This describes what trials gave people, not a recommendation. (Source 5)

If it is harmful, what reduces it?

Red clover is not stored in the body, so there is nothing to clear. Where harm has been reported, the review evidence points at what was in the product rather than at the plant, so the reducible risk is contamination and adulteration. A case report of a bleeding disorder following misuse is the main serious event described in an individual. (Source 3)

Why might someone be low in it or missing it?

Red clover isoflavones are not essential nutrients, so nobody is deficient in them. What varies is exposure: red clover is barely present in the ordinary diet, so intake comes almost entirely from supplements, and the amount actually delivered differs hugely between products because commercial preparations are not consistently standardised. (Source 3)

Which whole foods contain it or feed it?

Red clover is a forage crop rather than a normal human food, so almost no one gets it from meals. As a plant it is a rich isoflavone source, holding roughly 10 to 25 mg of isoflavones per gram of dry weight, several times the concentration in soybeans. Other isoflavone-containing legumes that are eaten include soy, alfalfa and beans. (Source 9)

What happens if you do not have it?

Nothing happens. There is no deficiency state, disease or symptom attributed to not taking red clover. Since the research has not established a conclusive benefit for any condition, no consequence of absence has been demonstrated either. (Source 4)

How can you test for it?

There is no clinical test for red clover status, and the literature we searched describes none. What is tested is the product, not the person: analytical work measures isoflavone content and contaminants in supplements, and reviewers call for standardisation on aglycone isoflavone equivalents precisely because labels and contents have not matched. (Source 3)

References

1. PLOS ONE. Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review. 2013. PMID 24312387, DOI 10.1371/journal.pone.0081968. Read the source
2. Frontiers in Emergency Medicine. Coagulation Disorder following Red Clover (Trifolium Pratense) Misuse: a Case Report. 2018. PMID 31172083. Read the source
3. African Journal of Pharmacy and Pharmacology. The safety, efficacy, and quality of Trifolium pratense (Red clover) for menopause relief. 2026. Read the source
4. National Center for Complementary and Integrative Health (NCCIH), US National Institutes of Health. Red Clover. 2025. Read the source
5. Nutrients. 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. 2021. DOI 10.3390/nu13041258. Read the source
6. EFSA Journal (European Food Safety Authority), 2015;13(10):4246; adopted 21 October 2015. Risk assessment for peri- and post-menopausal women taking food supplements containing isolated isoflavones. 2015. DOI 10.2903/j.efsa.2015.4246. Read the source
7. Avicenna Journal of Phytomedicine. Effects of red clover on hot flash and circulating hormone concentrations in menopausal women: a systematic review and meta-analysis. 2015. PMID 26693407. Read the source
8. Nutrients. Role of Phytoestrogen-Rich Bioactive Substances (Linum usitatissimum L., Glycine max L., Trifolium pratense L.) in Cardiovascular Disease Prevention in Postmenopausal Women: A Systematic Review and Meta-Analysis. 2022. DOI 10.3390/nu14122467. Read the source
9. Nutrients. Scientific Evidence Supporting the Beneficial Effects of Isoflavones on Human Health. 2020. DOI 10.3390/nu12123853. Read the source