Drug & supplement interaction

Niacinamide + Dicumarol

Dicumarol brand name: Dicumarol.

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

Niacinamide has a moderate interaction with Dicumarol. Theoretically, niacinamide may have additive effects when used with anticoagulant or antiplatelet drugs, especially in patients on hemodialysis.

Read the full interaction report
SeverityModerate
LikelihoodUnlikely
EvidenceD
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Niacinamide 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 Niacinamide interacts with.

Theoretically, niacinamide may have additive effects when used with anticoagulant or antiplatelet drugs, especially in patients on hemodialysis.
Several cases of thrombocytopenia have been reported for hemodialysis patients treated with niacinamide 1 gram daily. Hemodialysis patients receiving niacinamide had almost a three-fold higher risk of developing thrombocytopenia when compared with those receiving placebo.
Severity Moderate Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

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

Let me put this one in plain terms. Dicumarol is a blood thinner, much like warfarin, and it works by slowing your body's ability to form clots. The concern here is that high-dose niacinamide (the amounts seen in studies were around 1 gram a day, far above what you'd get from food or a basic vitamin) may add to that blood-thinning effect. In some hemodialysis patients, niacinamide was linked to a drop in platelets, the tiny cells that help you stop bleeding.

Honestly, this is a theoretical concern backed only by scattered case reports, so for most people it's unlikely to be a big deal. Still, since Dicumarol has a narrow safety window, watch for easy bruising, nosebleeds, or unusual bleeding, and check with your pharmacist or doctor before adding concentrated niacinamide.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Rottembourg JB, Launay-Vacher V, Massard J. Thrombocytopenia induced by nicotinamide in hemodialysis patients. Kidney Int. 2005;68(6):2911-2. PubMed
  2. Zhang Y, Ma T, Zhang P. Efficacy and safety of nicotinamide on phosphorus metabolism in hemodialysis patients: A systematic review and meta-analysis. Medicine (Baltimore). 2018;97(41):e12731. 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

Niacinamide Also Interacts With Other Medications

Niacinamide has 123 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 123 No known interaction 2,707 (incl. Dicumarol)
Taking anything else?

Check Another of Your Medications Against Niacinamide

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

Everything else you take

See Every Supplement That Interacts With Dicumarol

This page covers Niacinamide 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

One more smart check

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

We hold 552 real supplement products containing Niacinamide, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Niacinamide. Your product may carry other ingredients that interact with Dicumarol too, on top of Niacinamide — 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 Niacinamide 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 Niacinamide
Top 25%

#301 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 Niacinamide

What is Niacinamide?

  • Acne and skin health
  • Pellagra (niacin deficiency)
  • Anti-aging and skin tone
  • Rosacea
  • Protecting against certain skin cancers

Niacinamide (also called nicotinamide) is a form of vitamin B3 used in supplements and skin-care products. It is well established for preventing and treating vitamin B3 deficiency, and there is moderate evidence for some skin uses, but many popular claims are still being studied. It is generally well tolerated at usual doses, but high amounts should be discussed with your doctor or pharmacist.

Read the full Niacinamide monograph & all interactions
Keep checking

Other Drugs & Niacinamide

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

0Major
123Moderate
0Minor
2,706No known interaction
123 Moderate 2,706 No interaction
Moderate

123 interactions

Showing 60 of 123 moderate interactions — see all 123 on the Niacinamide page.

No interaction 2,706 drugs checked — show the list

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

Showing the 60 most looked-up of 2,706 medications checked with no known interaction — see the full Niacinamide list.

See the full Niacinamide 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
Niacinamide 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 Niacinamide and Dicumarol Together: Common Questions

Can you take Niacinamide 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 Niacinamide 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 Niacinamide?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.