Drug & supplement interaction

Flaxseed + Cefazolin

Cefazolin brand name: Ancef.

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

Flaxseed has a moderate interaction with Cefazolin. Theoretically, antibiotics might interfere with the metabolism of flaxseed constituents, which could potentially alter the effects of flaxseed.

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

Flaxseed and Cefazolin

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

Moderate

ANTIBIOTIC DRUGS

Why this applies to Cefazolin

Cefazolin falls under ANTIBIOTIC DRUGS — the group Flaxseed interacts with.

Theoretically, antibiotics might interfere with the metabolism of flaxseed constituents, which could potentially alter the effects of flaxseed.
Some potential benefits of flaxseed are thought to be due to its lignan content. Secoisolariciresinol diglucoside (SDG), a major lignan precursor, is found in high concentrations in flaxseed. SDG is converted by bacteria in the colon to the lignans enterolactone and enterodiol. Antibiotics alter the flora of the colon, which could theoretically alter the metabolism of flaxseed.
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 of this one: it's not about cefazolin getting stronger or weaker. Cefazolin (Ancef) is an injectable antibiotic that works by killing bacteria, including some of the friendly bacteria living in your gut. Those gut bacteria are exactly what turn the lignans in flaxseed into the active compounds (enterolactone and enterodiol) your body actually uses. So the concern runs the other direction: the antibiotic could blunt some of flaxseed's potential benefits, like its cholesterol or lignan-related effects, not cause a dangerous reaction.

This is purely theoretical, based on how things work on paper, so I wouldn't lose sleep over it. Flaxseed as a food is fine. If you take it for a specific health reason, just mention it to your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Thompson LU, Rickard SE, Cheung F, et al. Variability in anticancer lignan levels in flaxseed. Nutr Cancer 1997;27:26-30. PubMed
  2. Serraino M, Thompson LU. The effect of flaxseed supplementation on early risk markers for mammary carcinogenesis. Cancer Lett 1991;60:135-42. PubMed
  3. Rickard SE, Yuan YV, Thompson LU. Plasma insulin-like growth factor I levels in rats are reduced by dietary supplementation of flaxseed or its lignan secoisolariciresinol diglycoside. Cancer Lett 2000;161:47-55. PubMed
  4. Adlercreutz H, Fotsis T, Bannwart C, et al. Determination of urinary lignans and phytoestrogen metabolites, potential antiestrogens and anticarcinogens, in urine of women on various habitual diets. J Steroid Biochem 1986;25:791-7.. 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

Flaxseed Also Interacts With Other Medications

Flaxseed has 596 moderate known drug interactions in our database — the Cefazolin one above is one of them. If you take anything else, check it against the full list below.

Moderate 596 No known interaction 2,234 (incl. Cefazolin)
Taking anything else?

Check Another of Your Medications Against Flaxseed

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

From our Q&A

Questions About Flaxseed or Cefazolin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Flaxseed or Cefazolin, 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 Cefazolin

This page covers Flaxseed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cefazolin page lists 43 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Asarabacca (major), Siberian Cocklebur (major), African Wild Potato (moderate), Aristolochia (moderate) and Bacillus Coagulans (moderate).

By severity: 2 major · 39 moderate · 2 minor.

From our pharmacist’s overview on the Cefazolin page

“Cefazolin (Ancef), an antibiotic given by injection, usually before surgery or for skin and bloodstream infections, carries 43 supplement interactions on file, and the two rated major are where I would start reading. Siberian cocklebur and asarabacca can each damage the kidneys, the same organ that clears cefazolin, and asarabacca is f…”

Reviewed by 2 · Jul 18, 2026

Open the Cefazolin interaction page

One more smart check

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

We hold 236 real supplement products containing Flaxseed, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Flaxseed. Your product may carry other ingredients that interact with Cefazolin too, on top of Flaxseed — 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 Flaxseed and Cefazolin 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 Flaxseed
Top half

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

29 days ago today
Medication Cefazolin
Steady interest

#1,826 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 Flaxseed

What is Flaxseed?

Flaxseed
  • Constipation and digestive health
  • High cholesterol
  • Heart health
  • Menopausal symptoms
  • Blood sugar support

Flaxseed is a nutritious food rich in fiber, omega-3 fats (ALA), and plant compounds called lignans. It is most reliably helpful for constipation and may modestly lower cholesterol, but evidence for many other uses is mixed or limited. It is generally safe as a food, but talk to your pharmacist or doctor before using it as a supplement, especially if you are pregnant or breastfeeding.

Read the full Flaxseed monograph & all interactions
Medication

About Cefazolin Injection

What Is Cefazolin Injection Used For?

Brand name: Ancef

Cefazolin Injection is used to treat bacterial infections in adults and children 1 month of age and older, including respiratory tract infections, urinary tract infections, skin and skin structure infections, biliary tract infections, bone and joint infections, genital infections (such as prostatitis and epididymitis), septicemia (a serious bloodstream infection), and endocarditis (infection of the heart's inner lining).

It is also used in adult patients — and in pediatric patients aged 10 to 17 years for the premixed formulation — to help prevent infection around the time of surgery, particularly for procedures that carry a higher risk of postoperative infection.

See full Cefazolin Injection drug information
Keep checking

Other Drugs & Flaxseed

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

0Major
596Moderate
0Minor
2,233No known interaction
596 Moderate 2,233 No interaction
Moderate

596 interactions

Showing 60 of 596 moderate interactions — see all 596 on the Flaxseed page.

No interaction 2,233 drugs checked — show the list

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

Showing the 60 most looked-up of 2,233 medications checked with no known interaction — see the full Flaxseed list.

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

Can you take Flaxseed with Cefazolin?
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 Flaxseed and Cefazolin 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 Cefazolin and Flaxseed?

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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.