Drug & supplement interaction

Zinc + Cephalexin

Cephalexin brand names: Keflex, Keftab, Cephalex, Lexin.

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

Zinc has a moderate interaction with Cephalexin. Zinc might decrease cephalexin levels by chelating with cephalexin in the gut and preventing its absorption.

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

Zinc and Cephalexin

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

Moderate

CEPHALEXIN (Keflex)

Zinc might decrease cephalexin levels by chelating with cephalexin in the gut and preventing its absorption.
A pharmacokinetic study shows that zinc sulfate 250 mg taken concomitantly with cephalexin 500 mg decreases peak levels of cephalexin by 31% and reduces the exposure to cephalexin by 27%. Also, taking zinc sulfate 3 hours before cephalexin decreases peak levels of cephalexin by 11% and reduces the exposure to cephalexin by 18%. By decreasing cephalexin levels, zinc might increase the risk of treatment failure. This effect does not occur when zinc is taken 3 hours after the cephalexin dose. To avoid an interaction, advise patients take zinc sulfate 3 hours after taking cephalexin.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

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

Here's the practical takeaway: when you swallow zinc at the same time as your cephalexin, the zinc can grab onto the antibiotic in your gut and form a clump your body can't absorb well. In one study, taking them together knocked cephalexin blood levels down by about a third. That matters because cephalexin only works if enough of it actually reaches your bloodstream to fight the infection.

If too little gets absorbed, you risk the infection not clearing fully or coming back. The easy fix is timing: take your cephalexin first, then wait at least 3 hours before your zinc. That spacing avoided the problem in the research. Run your exact schedule by your pharmacist to be safe.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ding Y, Jia YY, Li F, et al. The effect of staggered administration of zinc sulfate on the pharmacokinetics of oral cephalexin. Br J Clin Pharmacol. 2012 Mar;73(3):422-7. 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

Zinc Also Interacts With Other Medications

Zinc has 62 moderate, 4 minor known drug interactions in our database — the Cephalexin one above is one of them. If you take anything else, check it against the full list below.

Moderate 62 Minor 4 No known interaction 2,764 (incl. Cephalexin)
Taking anything else?

Check Another of Your Medications Against Zinc

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

From our Q&A

Questions About Zinc or Cephalexin

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

This page covers Zinc only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cephalexin page lists 61 supplements it has a documented interaction with, worst first, each one explained.

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

By severity: 3 major · 47 moderate · 11 minor.

From our pharmacist’s overview on the Cephalexin page

“Cephalexin (Keflex) is one of the most commonly prescribed oral antibiotics, usually for skin and urinary infections, and its supplement list warrants genuine care rather than a quick skim. Three of the 61 ingredients on file rate major.”

Reviewed by 2 · Jul 18, 2026

Open the Cephalexin interaction page

One more smart check

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

We hold 26,692 real supplement products containing Zinc, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Zinc. Your product may carry other ingredients that interact with Cephalexin too, on top of Zinc — 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 Zinc and Cephalexin 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 Zinc
Top 10

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

29 days ago today
Medication Cephalexin
Top 5%

#67 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 Zinc

What is Zinc?

Zinc
  • Zinc deficiency
  • Immune support
  • Cold symptoms
  • Acne
  • Wound healing

Zinc is an essential mineral that your body needs for immune function, wound healing, taste, and smell. Most people get enough from food, but supplements can help correct or prevent a deficiency. Taking too much zinc for too long can cause harm, so check with a pharmacist or doctor before using high-dose supplements.

Read the full Zinc monograph & all interactions
Medication

About Cephalexin

What Is Cephalexin Used For?

Brand names: Keflex, Keftab, Cephalex, Lexin

Cephalexin treats bacterial infections caused by susceptible strains of bacteria. It is used for respiratory tract infections, ear infections (otitis media), skin and skin structure infections, bone infections, and genitourinary tract infections — including acute prostatitis.

It works only against bacterial infections — not viruses like colds or flu. Your prescriber should use it only when a bacterial infection is confirmed or strongly suspected, to help prevent antibiotic resistance.

See full Cephalexin drug information
Keep checking

Other Drugs & Zinc

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

0Major
62Moderate
4Minor
2,763No known interaction
62 Moderate 4 Minor 2,763 No interaction
Moderate

62 interactions

Showing 60 of 62 moderate interactions — see all 62 on the Zinc page.

Minor

4 interactions

No interaction 2,763 drugs checked — show the list

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

Showing the 60 most looked-up of 2,763 medications checked with no known interaction — see the full Zinc list.

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

Can you take Zinc with Cephalexin?
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 Zinc and Cephalexin 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 Cephalexin and Zinc?

Our pharmacists answer your medication & supplement questions — free.

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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.