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Moderate evidenceHeart & metabolic

Horse Chestnut

Standardized horse chestnut seed extract (dosed by its aescin content) is one of the better-supported oral options for chronic venous insufficiency, with Cochrane finding consistent reductions in leg pain and leg volume. The trials are old, small and mostly manufacturer-run, and raw horse chestnut is genuinely toxic.

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What the science says

  • Reduces leg pain in chronic venous insufficiency Moderate evidence

    The Cochrane review of 17 RCTs found six of seven placebo-controlled trials reported significantly less leg pain with horse chestnut seed extract; the one trial reporting a pooled figure gave a weighted mean difference of 42.4 mm on a 100 mm visual analogue scale (95% CI 34.9 to 49.9) — an effect so large it should be read as a single-trial outlier rather than the expected result.

  • Reduces leg volume and oedema Moderate evidence

    Six placebo-controlled trials (n = 502) pooled to a weighted mean difference of 32.1 mL less leg volume (95% CI 13.5 to 50.7) with horse chestnut extract. One trial suggested it may be roughly as effective as compression stockings — useful for people who cannot tolerate compression, though the trial was small. Cochrane's verdict: efficacious and safe for short-term use, but larger definitive RCTs are still needed.

  • No evidence for varicose vein appearance, ulcer healing or long-term disease modification Limited evidence

    Trials ran 2-16 weeks and measured symptoms and volume. Nothing shows horse chestnut shrinks visible varicosities, heals venous ulcers, or slows progression of venous disease. The broader 2020 Cochrane phlebotonics review found no class effect on ulcer healing (RR 0.94) or quality of life (SMD -0.06).

Dosage & safety

Studied doseTrials used extract standardized to 16-20% triterpene glycosides delivering 50 mg aescin twice daily (100 mg aescin/day), typically 250-313 mg extract per dose, for 2-16 weeks; slow-release formulations were common. Whole seed powder, tinctures and "horse chestnut complex" products are not equivalent and are not standardized to aescin.
SafetyStandardized extract causes mild, infrequent adverse events: GI upset, dizziness, headache, itching. The critical warning is about the raw plant — unprocessed horse chestnut seeds (conkers), leaves, bark and flowers contain esculin, which is toxic and has caused poisoning in children who ate them; only properly processed, esculin-free standardized extract is safe to take. Aescin has additive theoretical risk with anticoagulants and antiplatelets — discuss with a clinician if you take warfarin, a DOAC or aspirin. Avoid with renal or hepatic impairment (rare renal injury reported with high-dose parenteral aescin). Not established in pregnancy or breastfeeding. It does not replace compression therapy, and new or one-sided leg swelling requires ruling out DVT before self-treating.

How to take it

TimingTwice daily, morning and evening.
With food?With food, which reduces nausea and dizziness.
Worth knowingOnly properly processed, esculin-free standardized extract is safe — raw seeds, leaves and bark are toxic and have poisoned children who ate conkers.

Interactions

With medications

  • warfarin, DOACs, aspirin and clopidogrel

    Aescin adds theoretical antithrombotic effect on top of these drugs. discuss with a clinician before combining and stop before surgery

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does horse chestnut work for varicose veins and swollen legs?

Standardized horse chestnut seed extract has moderate evidence for chronic venous insufficiency: a Cochrane review found consistent reductions in leg pain, and pooled trials showed 32.1 mL less leg volume versus placebo. It has not been shown to shrink visible varicose veins or heal ulcers.

How much horse chestnut extract should I take?

Trials used horse chestnut extract standardized to deliver 50 mg aescin twice daily (100 mg aescin/day), typically 250-313 mg of extract per dose, for 2-16 weeks. Whole seed powder and tinctures are not equivalent.

Is horse chestnut poisonous?

Raw horse chestnut is: the seeds (conkers), leaves, bark and flowers contain toxic esculin and have poisoned children who ate them. Only properly processed, esculin-free standardized horse chestnut extract is safe to take.

Can I take horse chestnut with blood thinners?

Discuss it with a clinician first: aescin in horse chestnut adds a theoretical antithrombotic effect to warfarin, DOACs, aspirin and clopidogrel. Stop it before surgery, and avoid horse chestnut with kidney or liver impairment.

Scientific references

Where to buy

Swanson Vitamins, Horse Chestnut Extract, 250 mg, 120 Capsules

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