Drug & supplement interaction

Sweet Vernal Grass + Dicumarol

Dicumarol brand name: Dicumarol.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Sweet Vernal Grass has a moderate interaction with Dicumarol. Hay prepared from dried sweet vernal grass contains an anticoagulant, dicoumarol, which has been associated with fatal hemorrhages in animals.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Sweet Vernal Grass and Dicumarol

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Dicumarol

Dicumarol falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Sweet Vernal Grass interacts with.

Hay prepared from dried sweet vernal grass contains an anticoagulant, dicoumarol, which has been associated with fatal hemorrhages in animals. Theoretically, taking dried sweet vernal grass might cause additive effects and side effects with drugs having anticoagulant or antiplatelet properties.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's something a little ironic: Dicumarol is actually a relative of the very compound found in Sweet Vernal Grass. When this grass spoils or molds, its coumarin can convert into dicoumarol, the same blood-thinning chemical your medication is based on. So in theory, taking the two together could stack one blood thinner on top of another.

That could push your blood toward thinning too much, raising the risk of easy bruising, nosebleeds, bleeding gums, or harder-to-stop bleeding. Keep in mind this warning is theoretical, based on how these chemicals behave rather than human studies, and Dicumarol is already a tricky drug to dose. Please don't start any grass supplement without checking with your doctor or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Sweet Vernal Grass Also Interacts With Other Medications

Sweet Vernal Grass has 121 moderate known drug interactions in our database — the Dicumarol one above is one of them. If you take anything else, check it against the full list below.

Moderate 121 No known interaction 2,709 (incl. Dicumarol)
Taking anything else?

Check Another of Your Medications Against Sweet Vernal Grass

Covers the 2,830 medications we’ve checked against Sweet Vernal Grass. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Dicumarol

This page covers Sweet Vernal Grass only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Dicumarol page lists 218 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Danshen (major), Piracetam (major), Aconite (moderate) and Allspice (moderate).

By severity: 3 major · 190 moderate · 25 minor.

From our pharmacist’s overview on the Dicumarol page

“Danshen tops my worry list for anyone taking dicumarol, an older blood thinner in the warfarin family. It has clot-blocking activity of its own, and stacking it on an anticoagulant can push bleeding risk too far.”

Reviewed by 2 · Jul 18, 2026

Open the Dicumarol interaction page

How much people look this up

Where Sweet Vernal Grass and Dicumarol Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Sweet Vernal Grass
Steady interest

#1,447 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Dicumarol
Steady interest

#2,200 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Sweet Vernal Grass

What is Sweet Vernal Grass?

  • Trouble sleeping
  • Mild anxiety or restlessness
  • Hay fever and allergy symptoms (as a known trigger, sometimes studied)
  • Used as a fragrant flavoring in foods and drinks
  • Folk use for nausea or upset stomach

Sweet Vernal Grass is a fragrant European meadow grass best known for the sweet, hay-like smell it gets from coumarin. It has a long history as a flavoring and a folk calming remedy, but there is very little human research to support any health benefit. It is also a well-known cause of grass-pollen allergies, so people prone to hay fever should be cautious.

Read the full Sweet Vernal Grass monograph & all interactions
Keep checking

Other Drugs & Sweet Vernal Grass

Browse every other medication we’ve checked against Sweet Vernal Grass — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
121Moderate
0Minor
2,708No known interaction
121 Moderate 2,708 No interaction
Moderate

121 interactions

Showing 60 of 121 moderate interactions — see all 121 on the Sweet Vernal Grass page.

No interaction 2,708 drugs checked — show the list

We also checked Sweet Vernal Grass against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,708 medications checked with no known interaction — see the full Sweet Vernal Grass list.

See the full Sweet Vernal Grass interactions page
See every supplement checked against Dicumarol, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

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

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

Keep exploring
Sweet Vernal Grass monograph › Uses, safety, and every drug interaction in one place Dicumarol supplement interactions › Every supplement checked against Dicumarol, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Sweet Vernal Grass and Dicumarol Together: Common Questions

Can you take Sweet Vernal Grass with Dicumarol?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Sweet Vernal Grass and Dicumarol interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Dicumarol and Sweet Vernal Grass?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.