Drug & supplement interaction

Evening Primrose + Dalteparin

Dalteparin brand name: Fragmin.

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

Evening Primrose has a moderate interaction with Dalteparin. Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.

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

Evening Primrose and Dalteparin

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

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Dalteparin

Dalteparin falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Evening Primrose interacts with.

Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Evening primrose oil contains gamma linolenic acid (GLA). There is preliminary clinical evidence that GLA can reduce platelet aggregation and prolong bleeding time.
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

Dalteparin (Fragmin) is already a powerful blood thinner that lowers your blood's ability to clot. Evening primrose oil contains GLA, and there's some early lab-level evidence that GLA can make platelets a little less sticky and lengthen how long it takes you to stop bleeding. Put the two together and, at least in theory, you could nudge your bleeding risk a bit higher.

I want to be clear that this concern is theoretical, based on how these substances behave rather than strong human studies. Still, since dalteparin is an injectable anticoagulant, it's worth paying attention. Watch for things like easy bruising, nosebleeds, bleeding gums, or unusually heavy bleeding. Before adding evening primrose, please check with your pharmacist or doctor so they can weigh it for your situation.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Guivernau M, Meza N, Barja P, Roman O. Clinical and experimental study on the long-term effect of dietary gamma-linolenic acid on plasma lipids, platelet aggregation, thromboxane formation, and prostacyclin production. Prostaglandins Leukot Essent Fatty A PubMed

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

Evening Primrose Also Interacts With Other Medications

Evening Primrose has 147 moderate, 85 minor known drug interactions in our database — the Dalteparin one above is one of them. If you take anything else, check it against the full list below.

Moderate 147 Minor 85 No known interaction 2,598 (incl. Dalteparin)
Taking anything else?

Check Another of Your Medications Against Evening Primrose

Covers the 2,830 medications we’ve checked against Evening Primrose. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Dalteparin

This page covers Evening Primrose only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Dalteparin 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 Dalteparin page

“Dalteparin (Fragmin) is an injectable blood thinner used to prevent and treat dangerous clots, which is exactly why this list warrants real vigilance, and nearly all 218 ingredients on it thin the blood too. They are herbs and extracts with clot-inhibiting or antiplatelet effects of their own, so stacking them on dalteparin can push bl…”

Reviewed by 2 · Jul 18, 2026

Open the Dalteparin interaction page

One more smart check

Taking Evening Primrose as Part of a Dietary Supplement Product? Check It for Interactions

We hold 98 real supplement products containing Evening Primrose, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Evening Primrose. Your product may carry other ingredients that interact with Dalteparin too, on top of Evening Primrose — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Evening Primrose and Dalteparin 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 Evening Primrose
Top half

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

29 days ago today
Medication Dalteparin
Steady interest

#1,418 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 Evening Primrose

What is Evening Primrose?

Evening Primrose
  • Eczema and skin health
  • PMS symptoms
  • Breast pain (mastalgia)
  • Menopause symptoms
  • Inflammation
  • Diabetic nerve pain

Evening primrose oil is a seed oil rich in gamma-linolenic acid (GLA), an omega-6 fatty acid, that is popularly used for skin conditions, PMS, and breast pain. The evidence behind most of these uses is mixed or weak, and it is not proven to be a reliable treatment for any condition. It is generally well tolerated for short-term use, but talk to your pharmacist or doctor before starting it, especially if you are pregnant or have a bleeding disorder.

Read the full Evening Primrose monograph & all interactions
Medication

About Dalteparin Injection

What Is Dalteparin Injection Used For?

Brand name: Fragmin

Fragmin (dalteparin) injection is used to prevent blood clots (deep vein thrombosis and pulmonary embolism) in patients having abdominal surgery, hip replacement surgery, or in medical patients who are severely immobile during a serious illness. It is also used to reduce the risk of dangerous complications from unstable angina and a type of heart attack called non-Q-wave myocardial infarction, given alongside aspirin.

Fragmin is also used for the extended treatment of symptomatic venous thromboembolism (VTE — blood clots in the veins or lungs) to prevent recurrence in adult cancer patients, and for the treatment of symptomatic VTE in children from birth (gestational age at least 35 weeks). Fragmin is not intended for the immediate (acute) treatment of VTE.

See full Dalteparin Injection drug information
Keep checking

Other Drugs & Evening Primrose

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

0Major
147Moderate
85Minor
2,597No known interaction
147 Moderate 85 Minor 2,597 No interaction
Moderate

147 interactions

Showing 60 of 147 moderate interactions — see all 147 on the Evening Primrose page.

Minor

85 interactions

Showing 60 of 85 minor interactions — see all 85 on the Evening Primrose page.

No interaction 2,597 drugs checked — show the list

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

Showing the 60 most looked-up of 2,597 medications checked with no known interaction — see the full Evening Primrose list.

See the full Evening Primrose interactions page
See every supplement checked against Dalteparin, 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
Evening Primrose monograph › Uses, safety, and every drug interaction in one place Dalteparin supplement interactions › Every supplement checked against Dalteparin, ranked by severity Dalteparin Injection 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 Evening Primrose and Dalteparin Together: Common Questions

Can you take Evening Primrose with Dalteparin?
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 Evening Primrose and Dalteparin 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 Dalteparin and Evening Primrose?

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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.