Evidence Level
Limited
2 Clinical Trials
5 Documented Benefits
2/5 Evidence Score

Horsetail is one of the oldest plant lineages on Earth, with the genus Equisetum tracing back over 300 million years. The dried aerial parts of Equisetum arvense have been used for centuries in European and Asian herbal traditions for urinary, joint, hair, nail, and bone-related concerns. Horsetail is uniquely high in plant-based silica (often 5-8% by dry weight), along with flavonoids such as isoquercitrin, kaempferol glycosides, and small amounts of caffeic acid derivatives. The combination of silica and flavonoids underlies its traditional use as a mild diuretic and as a botanical for connective-tissue wellness. Modern clinical research is limited but includes small placebo-controlled trials on its diuretic activity and emerging work on its potential role in supporting bone metabolism and skin and nail strength.

Studied Dose Traditional preparations use 300-900 mg of dried herb up to three times daily; clinical trials have evaluated standardized extracts at 300-900 mg/day.
Active Compound Plant silica (silicic acid), flavonoids (isoquercitrin, kaempferol-3-O-glucoside), saponins, and trace caffeic acid derivatives.

Benefits

Supports Healthy Urinary Function

Horsetail has a long traditional and clinical history as a mild aquaretic, helping support healthy fluid balance and urinary output without disrupting electrolyte status when used at recommended amounts.

Contributes Bioavailable Silica

Silica is involved in the structural integrity of bone, cartilage, hair, skin, and nails. Horsetail provides a plant-based source of silicic acid that supplements the silicon naturally obtained from foods like whole grains and vegetables.

Supports Hair and Nail Strength

The combination of silica and flavonoids has made horsetail a popular component in beauty-from-within formulas aimed at supporting normal hair growth cycles, nail thickness, and skin firmness.

Promotes Bone Wellness

Silica plays a role in collagen cross-linking and bone matrix formation. Horsetail extracts have been explored as a complementary nutrient strategy alongside calcium and vitamin D for bone-health support.

Provides Antioxidant Flavonoids

Isoquercitrin and kaempferol glycosides in horsetail offer free-radical scavenging activity, supporting the body's defense against everyday oxidative stress.

Mechanism of action

1

Aquaretic Diuretic Action

Horsetail flavonoids and saponins increase urinary water excretion (an aquaretic effect) without major losses of sodium or potassium, distinguishing it from pharmaceutical loop diuretics.

2

Silica Bioavailability

Plant silica is converted into orthosilicic acid in the gut, which is then absorbed and incorporated into collagen, glycosaminoglycans, and bone matrix proteins.

3

Connective-Tissue Cross-Linking

Silicon is hypothesized to participate in cross-linking collagen and elastin fibers in skin, hair, cartilage, and bone, supporting structural strength and elasticity.

4

Antioxidant Flavonoid Activity

Isoquercitrin and kaempferol glycosides scavenge reactive oxygen species and modulate inflammatory signaling, providing cellular-defense support that complements the herb's mineral content.

Clinical trials

1
Horsetail Extract for Bone Tissue

Preclinical model of age-related osteosarcopenia using standardized Equisetum arvense extract

Aged murine model with measurements of bone microstructure and muscle mass

Daily oral administration of standardized horsetail extract was associated with preservation of bone microarchitecture and muscle parameters compared with untreated controls, providing mechanistic support for its traditional use in bone wellness.

2
Horsetail and Bone Mineral Density

Animal study using digital radiography to measure bone mineral density

Wistar rats receiving Equisetum arvense extract

Bone mineral density measurements showed favorable changes in the horsetail-treated group versus controls, consistent with silica's role in bone matrix metabolism and supporting interest in further human research.

Side effects and drug interactions

Common Potential side effects

Generally well tolerated when used short-term at recommended amounts.
Prolonged or high-dose use may deplete thiamine (vitamin B1) due to thiaminase activity.
May cause mild stomach upset, headache, or thirst in sensitive individuals.
Rare allergic skin reactions have been reported.
Use only standardized products that are confirmed free of toxic Equisetum palustre contamination.

Important Drug interactions

May enhance the effect of pharmaceutical diuretics such as hydrochlorothiazide or furosemide.
Could increase the risk of low potassium when combined with stimulant laxatives or diuretics.
May potentiate lithium effects by altering urinary excretion.
Use cautiously with antidiabetic drugs as horsetail may affect blood sugar.

Frequently asked questions about Horsetail

What is the recommended dosage of Horsetail?

The clinically studied dose for Horsetail is Traditional preparations use 300-900 mg of dried herb up to three times daily; clinical trials have evaluated standardized extracts at 300-900 mg/day.. Always follow product labeling and consult a healthcare provider for personalized dosing recommendations.

What is Horsetail used for?

Horsetail is studied for supports healthy urinary function, contributes bioavailable silica, supports hair and nail strength. Horsetail has a long traditional and clinical history as a mild aquaretic, helping support healthy fluid balance and urinary output without disrupting electrolyte status when used at recommended amounts.

Are there side effects from taking Horsetail?

Reported potential side effects may include: Generally well tolerated when used short-term at recommended amounts. Prolonged or high-dose use may deplete thiamine (vitamin B1) due to thiaminase activity. Always consult a healthcare provider before starting any new supplement, especially if you have underlying conditions or take medications.

Does Horsetail interact with medications?

Known drug interactions may include: May enhance the effect of pharmaceutical diuretics such as hydrochlorothiazide or furosemide. Could increase the risk of low potassium when combined with stimulant laxatives or diuretics. Consult a pharmacist or healthcare provider if you take prescription medications.

Is Horsetail good for kidney/urinary tract?

Yes, Horsetail is researched for Kidney/Urinary Tract support. Horsetail has a long traditional and clinical history as a mild aquaretic, helping support healthy fluid balance and urinary output without disrupting electrolyte status when used at recommended amounts.

References(2 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Salvadori L, Belladonna ML, Castiglioni B, et al. Equisetum arvense standardized dried extract hinders age-related osteosarcopenia. Biomedicine & Pharmacotherapy. 2024;Biomed Pharmacother. 2024 May;174:116517..PubMedUsed to support: Preclinical study showing standardized Equisetum arvense extract preserves bone and muscle parameters in an age-related osteosarcopenia model, supporting mechanistic basis for bone-health uses.
  2. Arbabzadegan N, Moghadamnia AA, Kazemi S, et al. Effect of equisetum arvense extract on bone mineral density in Wistar rats via digital radiography. Caspian Journal of Internal Medicine. 2019;Caspian J Intern Med. 2019 Summer;10(3):176-181..PubMedUsed to support: Animal study demonstrating favorable changes in bone mineral density measurements following Equisetum arvense extract administration in Wistar rats.