Interactions on record — worth a quick check against your medications. Based on 1 of 2 ingredients. Check your meds →
Dietary supplement

Horsetail Grass Max-V Ingredients & Drug Interactions

by Douglas Laboratories

Horsetail Grass Max-V label
See full label image
Capsule Category: Botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Horsetail Grass Max-V against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Horsetail Grass Max-V is a dietary supplement by Douglas Laboratories 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 Herbal Extract. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Horsetail Grass Max-V by Douglas Laboratories

Ask about any prescription or over-the-counter medication and we check it for interactions with Horsetail Grass Max-V by Douglas Laboratories — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Horsetail Grass Max-V by Douglas Laboratories

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

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Aug 6, 2026

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.
  • No proprietary blends here — you can verify the dose of every single component.

Horsetail Grass Max-V contains 2 active ingredients: horsetail herbal extract and horsetail grass. Both come from the same plant and carry the same active properties — they work through diuretic (water-removing) and other plant compounds.

The product also contains cellulose and vegetable stearate as inactive filler and binding ingredients to hold the capsule together.

Does it work?

Couldn't assess
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 assessable

This is a single-ingredient Horsetail product and its label doesn't state a use — see Horsetail's own graded uses on its monograph.

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.

The evidence for horsetail is not established for the uses listed in our data. Effectiveness ratings for urinary incontinence, obesity, tonsillitis, and male-pattern hair loss (androgenic alopecia) are all rated as insufficient reliable evidence to rate.

That means the research we hold does not support a clear conclusion about whether it works for these purposes. Talk with your doctor or pharmacist if you're considering it for a specific health concern.

The evidence, ingredient by ingredient Horsetail

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 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Horsetail is caution-rated for short-term use in healthy adults, but long-term use and unverified products carry real risks. The most common side effects from oral use are abdominal bloating, increased bowel movements, and nausea.

Crude horsetail contains thiaminase, an enzyme that can cause thiamine (vitamin B1) deficiency with prolonged use — Canadian products are required to be thiaminase-free, but check your label. There is not enough safety data to use horsetail during pregnancy or while breastfeeding; the safety data advises against both.

Side effects, ingredient by ingredient Horsetail

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 1 matched ingredient 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 taking Horsetail Grass Max-V, check with your doctor or pharmacist if you take antidiabetes drugs (blood sugar medications), diuretic drugs (water pills), lithium, or HIV medications including nucleoside reverse transcriptase inhibitors and efavirenz. All carry moderate-severity interactions with horsetail.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no assessable stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

Horsetail Grass Max-V is a two-ingredient supplement with moderate interactions to watch for, especially if you take blood sugar medication, diuretics, lithium, or HIV drugs. Evidence for its effectiveness is not established in the data we hold.

If you're on any regular medications, run them through the checker on this page and confirm with your doctor or pharmacist before you start.

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 Jun 1, 2012.

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 Grass Max-V, straight from the product label.

Brand Douglas Laboratories
Barcode (UPC) 310539001080
Net contents 60 Vegetarian Capsule(s)
Market status On market
Date entered into DSLD Jun 1, 2012
DSLD ID 9727
Product type Botanical
Supplement form Capsule
Dietary claims / uses All Other
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 Grass Max-V by Douglas Laboratories, 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 Vegetarian Capsule(s)
Maximum serving Sizes:
1 Vegetarian Capsule(s)
Servings per container
60
UPC/BARCODE
310539001080
IngredientAmount% DV
Horsetail Herbal Extract300 mg--
Horsetail Grass100 mg--

Other ingredients: Cellulose, Vegetable 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.
General Statements

Horsetail (Equisetum arvense L.) concentrates minerals, particularly silica as silicon dioxide (SiO2) and silicic acid/silicate (Si[OH]2); also manganese, magnesium and potassium. This Horsetail extract is standardized at 7% silica (10% silicic acid).

Suggested/Recommended/Usage/Directions

Suggested Usage: As a dietary supplement, adults take 1 capsule daily between meals, or as advised by your healthcare professional. If digestive irritation occurs, take with meals.

Precautions

Stop use and consult your health care professional if allergic reactions occur.

Note: If pregnant or nursing consult your healthcare professional before using this product.

KEEP OUT OF REACH OF CHILDREN.

Tamper resistant package, do not use if outer seal is missing.

Brand IP Statement(s)

For optimal storage conditions, store in a cool, dry place. (59(0)-77(0)F/15(0)-25(0)C) (35-65% relative humidity)

General

Formula #77350

FDA Statement of Identity

Standardized Herbal Extract Supplement

Formula

Standardized Herbal Supplement 7% silica (10% silicic acid)

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Horsetail Grass Max-V by Douglas Laboratories label

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

Horsetail Grass Max-V label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Horsetail Grass Max-V by Douglas Laboratories

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

Serving size1 Vegetarian Capsule(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 Herbal Extract

Interacts with
188 drugs
300 mg per serving Form: silica

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 Herbal Extract monograph & interactions

Horsetail Grass

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 Grass monograph & interactions

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

Interaction report

Horsetail Grass Max-V by Douglas Laboratories Drug Interactions

Want to check YOUR meds against Horsetail Grass Max-V?

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 Herbal Extract 188

Individual Drug Interactions

The ingredients in Horsetail Grass Max-V interact with 188 drugs. Click any drug to see the details.

1 of the 2 ingredients in Horsetail Grass Max-V interact with drugs. Each result below shows which ingredient is responsible. Horsetail Herbal Extract

Each ingredient & the kinds of drugs it affects

For each ingredient in Horsetail Grass Max-V 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.

Horsetail Herbal Extract5 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
Horsetail Herbal Extract full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Horsetail Grass Max-V, from the product label.

Douglas Laboratories

See all Douglas Laboratories products
Name
Douglas Laboratories
Street Address
600 Boyce Road
City
Pittsburgh
State
PA
ZipCode
15205
Phone Number
1.800.245.4440
Web Address
www.douglaslabs.com
Pharmacist Counseling Corner

Horsetail Grass Max-V by Douglas Laboratories: Common Questions

Does Horsetail Grass Max-V by Douglas Laboratories interact with any medications?
Yes. Based on its ingredients, Horsetail Grass Max-V 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 Grass Max-V 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.
Can I take this while pregnant or breastfeeding?
No — the safety data advises against horsetail during pregnancy and while breastfeeding because there isn't enough data to know it's safe. Talk with your doctor or pharmacist about whether it's right for you.
What are the most common side effects?
The most common are abdominal bloating, increased bowel movements, and nausea when taken by mouth. Clinical research on horsetail safety is limited, so other effects may not be well documented.
Does this product contain thiaminase?
Crude horsetail does contain thiaminase, an enzyme that can cause thiamine deficiency with long-term use. Canadian products are required to be certified free from thiaminase-like activity, so check your label to see if yours meets that standard.
Does it actually work for urinary incontinence, hair loss, or weight?
The evidence isn't established for any of those uses in our data — they're all rated insufficient reliable evidence to rate. That means we don't have clear research showing it works for them.
Is this safe for long-term use?
The safety data notes it may be used short-term by healthy adults, but long-term use carries real risks. Talk with your doctor about how long is safe for your situation.

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 Grass Max-V label
Go deeper

The Full Monographs Behind Horsetail Grass Max-V’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Horsetail

Interacts with 188 drugs

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. It can cause thiamine (vitamin B1) loss w...

Read the full Horsetail monograph →
Sources

Sources & How We Checked

Horsetail Grass Max-V'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 14 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.

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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