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Dietary supplement

Horsetail 400 mg Ingredients & Drug Interactions

by Solaray

Capsule Category: Other Combinations
Most serious interaction: Moderate
The interaction bottom line Most serious interaction: Moderate

Horsetail 400 mg is a dietary supplement by Solaray with 2 active ingredients. Its ingredients are commonly taken for fluid retention (mild diuretic), urinary and bladder concerns, hair, skin, and nail support.Based on those ingredients, 188 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Horsetail. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

HelloPharmacist Scorecard of Horsetail 400 mg by Solaray

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 2 of its 2 active ingredients.
  • “Horsetail Aerial Parts Extract” is listed as a grouped ingredient — the label gives one combined amount (100 mg) without saying how much of each component you get.

This product contains 2 active ingredients: horsetail and silica (a mineral form of silicon). Horsetail is the aerial part of the plant—the above-ground stems and branches—supplied as an extract.

Silica is included for its mineral content. The capsule also contains cellulose and magnesium stearate as inactive ingredients (binder and flow agent).

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use.

Why this rating?
  • The label markets this product for: Hair, skin, and nail support.
  • We looked for evidence on: Aging skin, Androgenic alopecia, Hair growth, Nail strength, Skin elasticity.
  • The closest evidence on file: Horsetail is rated "Insufficient Reliable Evidence To Rate" for Androgenic alopecia (Natural Medicines).
  • Also on file: Silicon is rated "Insufficient Reliable Evidence To Rate" for Aging skin, Androgenic alopecia.

For silica, clinical evidence suggests it may be possibly effective for osteoporosis, though the data isn't conclusive. For hair loss (androgenic alopecia), dental health (peri-implantitis), and for horsetail's uses in urinary incontinence, obesity, and tonsillitis, the evidence isn't established in our data—meaning we don't have reliable clinical evidence to know whether these claims hold up.

The evidence, ingredient by ingredient Horsetail Silicon

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 2 of the 2 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 2 of 2.
  • General safety write-ups exist for 2 of 2.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Silica is generally well tolerated in food and supplements, though long-term safety at high doses isn't well studied. Horsetail is approved for short-term use in healthy adults, but long-term safety is unclear and unverified products carry real risks.

The most common side effects from horsetail are abdominal bloating, increased bowel movements, and nausea. Crude horsetail contains thiaminase, which can cause thiamine (vitamin B1) deficiency with prolonged use—though Canadian products are required to be certified thiaminase-free.

Rarely, a patient developed a skin rash (seborrheic dermatitis) after topical horsetail, thought to be caused by its nicotine content. During pregnancy, silica safety data advises against use; for horsetail, there isn't enough safety data, so the data advises against it as well.

While breastfeeding, silica safety has not been established and should be avoided; horsetail also lacks sufficient safety data and should be avoided. Talk with your doctor or pharmacist before use if you're pregnant or nursing.

Side effects, ingredient by ingredient Horsetail Silicon

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 2 matched ingredients can interact with medications — Horsetail.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: diabetes medications; lithium.
  • For scale: 188 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before you take this, double-check with your pharmacist if you're on nucleoside reverse transcriptase inhibitors (NRTIs) or efavirenz (antiretroviral drugs for HIV), antidiabetes drugs, diuretics (water pills), or lithium. Horsetail may interfere with how these work or increase your risk of low blood sugar or mineral imbalances.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Moderate medication interactions have been identified, and safety information is well characterized.

This product may be worth a conversation if you're interested in bone health, but only if you don't take antiretroviral drugs, antidiabetes medications, diuretics, or lithium. Short-term use in healthy adults seems generally well tolerated, though long-term safety isn't well studied.

Always check your exact medications with the tool on this page before starting, and avoid it during pregnancy and breastfeeding.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 2 of 2 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Apr 24, 2025.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Horsetail 400 mg, straight from the product label.

Brand Solaray
Barcode (UPC) 076280366662
Net contents 60 VegCap(s)
Market status On market
Date entered into DSLD Apr 24, 2025
DSLD ID 325992
Product type Other Combinations
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years)
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Horsetail 400 mg by Solaray, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 VegCap(s)
Maximum serving Sizes:
1 VegCap(s)
Servings per container
60
UPC/BARCODE
076280366662
IngredientAmount% DV
Silica40 mg--
Horsetail100 mg--
Horsetail Aerial Parts Extract100 mg--

Other ingredients: Cellulose, Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Brand IP Statement(s)

Solaray Est. 1973 A Brighter Way 1973

Formula

10% Silica

Discussion: Horsetail is well known for its mineral content, especially the essential trace of mineral silica. Silica is intended to provide nutritive support for healthy skin, hair and nails.

Formulation

+ Hair, skin, and nails

Since 1973, we've scoured the globe for the highest quality ingredients, connecting you with the most efficacious supplements that help you live brighter & embrace the moments that matter most.

FDA Statement of Identity

Dietary Supplement

Seals/Symbols

Lab Verified

Precautions

Warning: Do not use if safety seal is broken or missing.

Keep out of reach of children.

Keep your licensed health care practitioner informed when using this product.

Do not use if you have a kidney disorder.

California Residents only Warning: Reproductive harm - www.P65Warnings.ca.gov

Suggested/Recommended/Usage/Directions

Directions: Use only as directed. Take 1 VegCap daily with a meal or glass of water.

Storage

Store in a cool, dry place.

FDA Disclaimer Statement

These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure or prevent any disease.

General Statements

100% PCR Bottles

Vital extracts

See for yourself

Horsetail 400 mg by Solaray label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

What’s inside

The Ingredients in Horsetail 400 mg by Solaray

These are the 2 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 VegCap(s) Dosage formCapsule Servings per container60 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Horsetail

Interacts with
188 drugs
100 mg per serving

Horsetail is a traditional herb most often used as a mild diuretic and for hair, nail, and bone support, but high-quality human evidence is limited. I...

Horsetail monograph & interactions

Horsetail Aerial Parts Extract

Interacts with
188 drugs
100 mg per serving Form: Equisetum arvense Aerial Parts Extract

Horsetail is a traditional herb most often used as a mild diuretic and for hair, nail, and bone support, but high-quality human evidence is limited. I...

Horsetail Aerial Parts Extract monograph & interactions

Other (inactive) ingredients: Cellulose, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Horsetail 400 mg by Solaray Drug Interactions

Want to check YOUR meds against Horsetail 400 mg?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

Go to the checker
188Drugs
188 Moderate

Ingredients driving the most interactions

Horsetail 188

Each ingredient & the kinds of drugs it affects

For each ingredient in Horsetail 400 mg with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Horsetail5 drug types · 188 drugs

Antidiabetes Drugs

Theoretically, taking horsetail with antidiabetes drugs might increase the risk of hypoglycemia.
Equisetum myriochaetum has demonstrated hypoglycemic activity in clinical research. In an animal diabetic model, Equisetum giganteum had hypoglycemic effects. It is unclear whether other horsetail species have hypoglycemic effects.

Likelihood Possible Evidence D
Diuretic Drugs

Theoretically, taking horsetail with diuretic drugs might increase potassium loss and the risk of hypokalemia.
Laboratory research shows that various species of horsetail have diuretic properties. Due to its diuretic effects, there has been concern that taking horsetail along with potassium-depleting diuretics might increase the risk for hypokalemia. However, pharmacokinetic research in humans shows that taking horsetail 900 mg daily for 4 days does not affect urinary excretion of electrolytes, including potassium and sodium, despite having a diuretic effect similar to taking hydrochlorothiazide 25 mg daily. It is unclear if taking horsetail for a longer duration would affect electrolyte levels. Until more is known, use with caution.

Likelihood Possible Evidence D
Efavirenz (Sustiva)

Theoretically, horsetail might decrease the levels and clinical effects of efavirenz.
In two case reports, patients were found to have detectable viral loads when taking horsetail-containing supplements along with an antiretroviral regimen that included efavirenz. In one case, the antiretroviral regimen included zidovudine, lamivudine, and efavirenz; in the other case, the regimen consisted of emtricitabine, tenofovir disoproxil fumarate, and efavirenz. One month after discontinuing horsetail, the viral loads became undetectable in both cases. The exact mechanism of this interaction is unknown. It is also unclear if this interaction is specific to efavirenz or if it is related to various components of antiretroviral therapy.

Likelihood Possible Evidence D
Lithium

Theoretically, horsetail might increase the levels and adverse effects of lithium.
Animal research suggests that horsetail has diuretic properties. Theoretically, due to these potential diuretic effects, horsetail might reduce excretion and increase levels of lithium. The dose of lithium might need to be decreased.

Likelihood Possible Evidence D
Nucleoside Reverse Transcriptase Inhibitors (Nrtis)

Theoretically, horsetail might decrease the levels and clinical effects of NRTIs.
In two case reports, patients were found to have detectable viral loads when taking horsetail-containing supplements along with an antiretroviral therapy. In one case, the antiretroviral regimen included zidovudine, lamivudine, and efavirenz; in the other case, the regimen consisted of emtricitabine, tenofovir disoproxil fumarate, and efavirenz. One month after discontinuing the supplement, the viral loads became undetectable in both cases. The exact mechanism of these interactions is unknown. It is also unclear if these interactions are specific to NRTIs or if they are related to various components of antiretroviral therapy.

Likelihood Possible Evidence D
The maker

Brand information

Manufacturer and brand details for Horsetail 400 mg, from the product label.

Solaray

See all Solaray products
Name
Nutraceutical Corp.
Web Address
www.nutraceutical.com
Pharmacist Counseling Corner

Horsetail 400 mg by Solaray: Common Questions

Does Horsetail 400 mg by Solaray interact with any medications?
Yes. Based on its ingredients, Horsetail 400 mg has a known interaction with 188 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Horsetail 400 mg contains 2 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Will horsetail help my hair loss?
We don't have reliable clinical evidence yet to say whether horsetail works for androgenic alopecia (male or female pattern hair loss). The data we hold rates it as insufficient evidence, so it's an open question.
What are the most common side effects?
Abdominal bloating, increased bowel movements, and nausea are the most commonly reported side effects from horsetail. These are generally mild, but if they persist, stop the product and talk to your pharmacist.
Is it safe to take long-term?
Horsetail is approved for short-term use in healthy adults, but long-term safety isn't well established. If you're thinking of taking it for weeks or months, discuss that with your pharmacist first.
Can I take this if I'm pregnant or breastfeeding?
No. The safety data advises against both ingredients during pregnancy and breastfeeding. Talk with your doctor before taking this product if you're pregnant, planning to become pregnant, or nursing.
Does this product contain thiaminase?
The product is horsetail extract, and crude horsetail contains thiaminase, which can cause vitamin B1 deficiency with prolonged use. If this is a Canadian product, it must be certified thiaminase-free by law.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Horsetail 400 mg label
Sources

Sources & How We Checked

Horsetail 400 mg's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 33 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Silicon 19 references
  1. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2002.
  2. Jugdaohsingh R, Anderson SH, Tucker KL, et al. Dietary silicon intake and absorption. Am J Clin Nutr 2002;75:887-93. PubMed
  3. Ichiyanagi O, Sasagawa I, Adachi Y, et al. Silica urolithiasis without magnesium trisilicate intake. Urol Int 1998;61:39-42. PubMed
  4. Levison DA, Crocker PR, Banim S, Wallace DM. Silica stones in the urinary bladder. Lancet 1982;1:704-5. PubMed
  5. Lee MH, Lee YH, Hsu TH, et al. Silica stone--development due to long time oral trisilicate intake. Scand J Urol Nephrol 1993;27:267-9. PubMed
  6. Cruz Guerra, N. A., Gomez Garcia, M. A., Lovaco, Castellano F., Saez Garrido, J. C., Garcia, Cuerpo E., and Escudero, Barrilero A. [Silica urolithiasis: report of a new case]. Actas Urol.Esp 2000;24(2):202-204.
  7. Merget, R., Bauer, T., Kupper, H. U., Philippou, S., Bauer, H. D., Breitstadt, R., and Bruening, T. Health hazards due to the inhalation of amorphous silica. Arch Toxicol. 2002;75(11-12):625-634. PubMed
  8. Khuder, S. A., Peshimam, A. Z., and Agraharam, S. Environmental risk factors for rheumatoid arthritis. Rev Environ Health 2002;17(4):307-315. PubMed
  9. McLaughlin, J. K., Chow, W. H., and Levy, L. S. Amorphous silica: a review of health effects from inhalation exposure with particular reference to cancer. J Toxicol.Environ Health 4-25-1997;50(6):553-566. DOI
  10. Pelucchi, C., Pira, E., Piolatto, G., Coggiola, M., Carta, P., and La, Vecchia C. Occupational silica exposure and lung cancer risk: a review of epidemiological studies 1996-2005. Ann.Oncol. 2006;17(7):1039-1050. PubMed
  11. Gillissen, A., Gessner, C., Hammerschmidt, S., Hoheisel, G., and Wirtz, H. [Health significance of inhaled particles]. Dtsch.Med Wochenschr. 3-24-2006;131(12):639-644.
  12. Hu, J. F., Qu, H., and Wang, J. Z. [Meta analysis for relationship between exposure of free silicon dioxide and lung tumor]. Zhonghua Lao.Dong.Wei Sheng Zhi.Ye.Bing.Za Zhi. 2006;24(7):415-417.
  13. Jugdaohsingh, R. Silicon and bone health. J Nutr Health Aging 2007;11(2):99-110.
  14. Lacasse, Y., Martin, S., Gagne, D., and Lakhal, L. Dose-response meta-analysis of silica and lung cancer. Cancer Causes Control 2009;20(6):925-933. PubMed
  15. McCormic, Z. D., Khuder, S. S., Aryal, B. K., Ames, A. L., and Khuder, S. A. Occupational silica exposure as a risk factor for scleroderma: a meta-analysis. Int Arch Occup.Environ Health 2010;83(7):763-769. PubMed
  16. Haddad, F. S. and Kouyoumdjian, A. Silica stones in humans. Urol.Int 1986;41(1):70-76. PubMed
  17. Tervaert, J. W., Stegeman, C. A., and Kallenberg, C. G. Silicon exposure and vasculitis. Curr Opin.Rheumatol 1998;10(1):12-17. PubMed
  18. Steenland, K. and Stayner, L. Silica, asbestos, man-made mineral fibers, and cancer. Cancer Causes Control 1997;8(3):491-503. PubMed
  19. Boqué N, Valls RM, Pedret A, Puiggrós F, Arola L, Solà R. Relative absorption of silicon from different formulations of dietary supplements: a pilot randomized, double-blind, crossover post-prandial study. Sci Rep 2021;11(1):16479. PubMed

See these in context on the Silicon monograph →

Horsetail 14 references
  1. Sudan BJ. Seborrhoeic dermatitis induced by nicotine of horsetails (Equisetum arvense L.). Contact Dermatitis 1985;13:201-2.
  2. Perez Gutierrez RM, Laguna GY, Walkowski A. Diuretic activity of Mexican equisetum. J Ethnopharmacol 1985;14:269-72. PubMed
  3. Lemus I, Garcia R, Erazo S, et al. Diuretic activity of an Equisetum bogotense tea (Platero herb): evaluation in healthy volunteers. J Ethnopharmacol 1996;54:55-8. PubMed
  4. Revilla MC, Andrade-Cetto A, Islas S, Wiedenfeld H. Hypoglycemic effect of Equisetum myriochaetum aerial parts on type 2 diabetic patients. J Ethnopharmacol 2002;81:117-20. PubMed
  5. Tiktinskii, O. L. and Bablumian, I. A. [Therapeutic action of Java tea and field horsetail in uric acid diathesis]. Urol.Nefrol.(Mosk) 1983;3(1):47-50.
  6. Henderson JA, Evans EV, and McIntosh RA. The antithiamine action of Equisetum. J Amer Vet Med Assoc 1952;120:375-378.
  7. Carneiro DM, Freire RC, Honório TC, Zoghaib I, Cardoso FF, Tresvenzol LM, de Paula JR, Sousa AL, Jardim PC, da Cunha LC. Randomized, Double-Blind Clinical Trial to Assess the Acute Diuretic Effect of Equisetum arvense (Field Horsetail) in Healthy Voluntee
  8. Klnçalp S, Ekiz F, Basar Ö, Coban S, Yüksel O. Equisetum arvense (Field Horsetail)-induced liver injury. Eur J Gastroenterol Hepatol. 2012 Feb;24(2):213-4. PubMed
  9. Ortega García JA, Angulo MG, Sobrino-Najul EJ, Soldin OP, Mira AP, Martínez-Salcedo E, Claudio L. Prenatal exposure of a girl with autism spectrum disorder to 'horsetail' (Equisetum arvense) herbal remedy and alcohol: a case report. J Med Case Rep. 2011 M PubMed
  10. Cordova E, Morganti L, Rodriguez C. Possible Drug-Herb Interaction between Herbal Supplement Containing Horsetail (Equisetum arvense) and Antiretroviral Drugs. J Int Assoc Provid AIDS Care. 2017;16(1):11-13.
  11. García Gavilán MD, Moreno García AM, Rosales Zabal JM, Navarro Jarabo JM, Sánchez Cantos A. Case of drug-induced acute pancreatitis produced by horsetail infusions. Rev Esp Enferm Dig. 2017 Apr;109(4):301-304. PubMed
  12. Vieira GT, de Oliveira TT, Carneiro MAA, et al. Antidiabetic effect of Equisetum giganteum L. extract on alloxan-diabetic rabbit. J Ethnopharmacol. 2020;260:112898. PubMed
  13. Health Canada. Organism-Equisetum arvense. Available at: http://webprod.hc-sc.gc.ca/nhpid-bdipsn/ingredReq.do?id=6117&lang=eng. Accessed 21-July 2021.
  14. Bates D, Duong TB, Kheyson S, Moore K. Hyponatremia Secondary to Decreased Oral Intake and SIADH and Possibly Exacerbated by Horsetail (Equisetum arvense). Can J Hosp Pharm 2021;74(4):386-389. PubMed

See these in context on the Horsetail monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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