Drug & supplement interaction

Sweet Vernal Grass + Diclofenac Sodium

Diclofenac Sodium brand names: Voltaren XR, Voltaren, Voltaren SR, Diclo, Difenac, and others.

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

Sweet Vernal Grass has a moderate interaction with Diclofenac Sodium. 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 Diclofenac Sodium

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

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Diclofenac Sodium

Diclofenac Sodium 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 the simple version. When sweet vernal grass is dried (think hay), some of its coumarin can turn into dicoumarol, a blood-thinning compound. Diclofenac is an NSAID, and on its own it can make it a little harder for your blood to clot and can be rough on the stomach lining. So in theory, pairing the two could add up and raise your risk of bleeding or bruising.

The important thing to know is that this is only a theoretical concern, based on how these compounds behave, not on real cases in people. Still, watch for signs like easy bruising, nosebleeds, dark or bloody stools, or stomach pain. If you take diclofenac regularly and want to use this supplement, please run it by your pharmacist or doctor 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 Diclofenac Sodium 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. Diclofenac Sodium)
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.

From our Q&A

Questions About Sweet Vernal Grass or Diclofenac Sodium

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Sweet Vernal Grass or Diclofenac Sodium, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Diclofenac Sodium

This page covers Sweet Vernal Grass only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Diclofenac Sodium page lists 308 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Beer (major), Danshen (major) and Piracetam (major).

By severity: 7 major · 266 moderate · 35 minor.

From our pharmacist’s overview on the Diclofenac Sodium page

“Diclofenac (Voltaren), a daily mainstay for arthritis and joint pain, comes with a supplement list that calls for real vigilance. Of the 308 ingredients on file, 7 rate major, and roughly two hundred entries share a single theme: anything with blood-thinning activity adds to diclofenac's own bleeding risk, especially in the stomach.”

Reviewed by 2 · Jul 18, 2026

Open the Diclofenac Sodium interaction page

How much people look this up

Where Sweet Vernal Grass and Diclofenac Sodium 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
Top 25%

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

29 days ago today
Medication Diclofenac Sodium
Top 25%

#394 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
Medication

About Diclofenac

What Is Diclofenac Used For?

Brand names: Voltaren XR, Voltaren, Voltaren SR, Diclo, Difenac, Diclo SR, Voltarol, Acoflam, Defenac, Dicloflex, Diclovol, Diclozip, Fenactol, Flamrase, Volraman, Diclomax SR, Diclomax Retard, Motifene 75 mg, Voltarol 75 mg SR, Acoflam 75 SR, Defenac SR, Dexomon 75 SR, Dicloflex 75 SR, Diclovol SR, Fenactol 75 mg SR, Flamatak 75 MR, Flamrase SR, Flexotard MR 75, Rheumatac Retard 75, Rhumalgan CR, Slofenac SR, Volsaid Retard 75, Voltarol Retard, Acoflam Retard, Defenac Retard, Dexomon Retard 100, Dicloflex Retard, Diclovol Retard, Fenactol Retard 100 mg, Flamatak 100 MR, Volsaid Retard 100, Voltarol Ophtha Multidose, Voltarol Ophtha, Pennsaid, Voltaren Emulgel, Dyloject

Diclofenac comes in many forms, and each one is approved for different uses. Which one you get depends on what you are treating.

  • Oral tablets: osteoarthritis, rheumatoid arthritis, and (delayed-release) ankylosing spondylitis, plus period pain and mild to moderate pain for the immediate-release potassium tablets.
  • Capsules: mild to moderate acute pain in adults.
  • Oral solution (powder for solution): acute treatment of migraine attacks in adults.
  • Topical gel and solution: osteoarthritis pain, mainly of the knees (and hands for the gel).
  • Skin patches (Flector, diclofenac epolamine): acute pain from minor strains, sprains and bruises.
See full Diclofenac drug information
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 Diclofenac Sodium, 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 Diclofenac Sodium supplement interactions › Every supplement checked against Diclofenac Sodium, ranked by severity Diclofenac drug information › The full plain-English guide to this medication 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 Diclofenac Sodium Together: Common Questions

Can you take Sweet Vernal Grass with Diclofenac Sodium?
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 Diclofenac Sodium 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 Diclofenac Sodium 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.