Drug & supplement interaction

Fasting + Aspirin

Aspirin brand names: Children's Aspirin, Easprin, Ecotrin, ASA, Asaphen, and others.

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

Fasting has a moderate interaction with Aspirin. Fasting 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?
Know someone interested in this? Share
Facebook Post Reddit Email
On this page
Interaction report

Fasting and Aspirin

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

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Aspirin

Aspirin falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Fasting interacts with.

Fasting may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Fasting has been found to increase the international normalized ratio (INR) in patients stabilized on warfarin. Closely monitor patients who are fasting while taking anticoagulant or antiplatelet drugs. Dose adjustment may be necessary.
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 gist with aspirin and fasting: aspirin already thins the blood a bit by keeping platelets from sticking together, which is great for preventing clots but also means a higher chance of bleeding. The concern on file is that going without food for stretches of time may nudge that bleeding risk up a little further. Think along the lines of easier bruising, a stomach upset, or bleeding that takes longer to stop.

I want to be honest about the strength here: this is mostly anecdotal, and the clearest signal came from warfarin patients, not aspirin specifically. So please don't panic. If you're fasting and take aspirin regularly, just mention it to your pharmacist or doctor and watch for any unusual bruising or bleeding.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Wilhelmi de Toledo F, Grundler F, Bergouignan A, Drinda S, Michalsen A. Safety, health improvement and well-being during a 4 to 21-day fasting period in an observational study including 1422 subjects. PLoS One. 2019;14(1):e0209353. PubMed
  2. Katada Y, Nakagawa S, Nishimura A, et al. Effects of fasting on warfarin sensitivity index in patients undergoing cardiovascular surgery. Eur J Clin Pharmacol. 2019;75(4):561-568. PubMed
  3. Lai YF, Cheen MHH, Lim SH, et al. The effects of fasting in Muslim patients taking warfarin. J Thromb Haemost. 2014;12(3):349-54. 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

Fasting Also Interacts With Other Medications

Fasting has 2 major, 205 moderate known drug interactions in our database — the Aspirin one above is one of them. If you take anything else, check it against the full list below.

Major 2 Moderate 205 No known interaction 2,623 (incl. Aspirin)
Taking anything else?

Check Another of Your Medications Against Fasting

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

Everything else you take

See Every Supplement That Interacts With Aspirin

This page covers Fasting only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Aspirin page lists 242 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 · 206 moderate · 29 minor.

From our pharmacist’s overview on the Aspirin page

“Aspirin thins the blood on purpose, and most of the 242 supplements and herbs on this page push that same effect further, so genuine care is warranted here rather than a shrug. Just over 200 of the entries can add to aspirin's antiplatelet action and raise the odds of bruising or bleeding, particularly in the stomach.”

Reviewed by 2 · Jul 18, 2026

Open the Aspirin interaction page

How much people look this up

Where Fasting and Aspirin 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 Fasting
Top half

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

29 days ago today
Medication Aspirin
Top 1%

#17 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.

Eating pattern

About Fasting

What is Fasting?

  • Weight loss
  • Blood sugar control
  • Heart health
  • Religious or spiritual practice
  • General wellness and longevity

Fasting means voluntarily going without food (and sometimes drink) for set periods. Some research suggests it may help with weight loss and blood sugar in certain people, but results vary and quality of evidence is mixed. It is not safe for everyone, so check with your doctor or pharmacist before starting—especially if you take medication or have a health condition.

Read the full Fasting monograph & all interactions
Medication

About Aspirin Rectal

What Is Aspirin Rectal Used For?

Brand names: Children's Aspirin, Easprin, Ecotrin, ASA, Asaphen, Aspirin, Gencardia, Micropirin, Angettes 75, Caprin, Nu-Seals Aspirin, Resprin, Durlaza, Cartia

Aspirin rectal suppositories are used to relieve pain and reduce fever in adults. They offer an alternative route for people who may have difficulty taking aspirin by mouth.

Children under 12 should not use this product without first consulting a physician.

See full Aspirin Rectal drug information
Keep checking

Other Drugs & Fasting

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

2Major
205Moderate
0Minor
2,622No known interaction
2 Major 205 Moderate 2,622 No interaction
Major

2 interactions

Moderate

205 interactions

Showing 60 of 205 moderate interactions — see all 205 on the Fasting page.

No interaction 2,622 drugs checked — show the list

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

Showing the 60 most looked-up of 2,622 medications checked with no known interaction — see the full Fasting list.

See the full Fasting interactions page
See every supplement checked against Aspirin, 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
Fasting monograph › Uses, safety, and every drug interaction in one place Aspirin supplement interactions › Every supplement checked against Aspirin, ranked by severity Aspirin Rectal 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

Following Fasting While Taking Aspirin: Common Questions

Can you follow Fasting while taking Aspirin?
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 Fasting and Aspirin 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 Aspirin and Fasting?

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.