Horsetail

Equisetum arvense · Field horsetail

Snapshot

Indications	Contraindications
Urinary tract flushing¹ Diuresis in healthy adults² Stage I hypertension³ Overactive bladder, combination⁴ Superficial wounds¹ Nail psoriasis, topical combination^{5, 6}	Pregnancy or breastfeeding⁷ Conditions requiring fluid restriction¹ Hypersensitivity to horsetail¹

Horsetail (Equisetum arvense) is a silicon-rich perennial whose above-ground stem is taken as tea, powder, capsule, or liquid extract. The effect that drives supplementation is diuresis, which in healthy men was comparable to hydrochlorothiazide. The European Medicines Agency monograph lists traditional use for flushing the urinary tract in minor urinary complaints¹. It also lists traditional use for superficial wounds¹. Trials extend to mild hypertension and, in combination products, overactive bladder symptoms.

The trials are small. A 2022 randomized trial in stage I hypertension found a standardized extract lowered blood pressure comparably to hydrochlorothiazide over three months³. In breast cancer cell lines, a 2024 laboratory study of hair-growth nutraceuticals found horsetail did not interfere with tamoxifen's inhibition of estrogen-driven proliferation; no human trial has tested this⁸. Products listing horsetail are mostly liquids, capsules, and powders; see Form comparison.

The European monograph excludes use where reduced fluid intake is recommended, such as severe cardiac or renal disease, because the use is flushing¹. Health Canada labels ask for a practitioner's advice before use with cardiac glycosides or antiarrhythmic agents⁷.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

35 sources, 28 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources