Drug & supplement interaction

Grapefruit + Moxifloxacin

Moxifloxacin brand name: Avelox.

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

Moxifloxacin falls into 2 drug categories that Grapefruit can interact with; the most serious is rated major. Grapefruit or grapefruit juice, especially if consumed in large amounts, can cause additive QT interval prolongation when taken with QT interval-prolonging drugs, potentially increasing the risk of ventricular arrhythmias.

Read the full interaction report
SeverityMajor
LikelihoodProbable
Interactions2
EvidenceB
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Grapefruit and Moxifloxacin

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Grapefruit interacts with whole categories of medication. Moxifloxacin falls into 2 of those categories, so it can interact with Grapefruit in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Major).

Major

QT INTERVAL-PROLONGING DRUGS

1 of 2

Why this applies to Moxifloxacin

Moxifloxacin falls under QT INTERVAL-PROLONGING DRUGS — the group Grapefruit interacts with.

Grapefruit or grapefruit juice, especially if consumed in large amounts, can cause additive QT interval prolongation when taken with QT interval-prolonging drugs, potentially increasing the risk of ventricular arrhythmias.
Clinical research in healthy volunteers shows that drinking 6 liters of grapefruit juice over 6 hours prolonged the QTc by a peak amount of 14 milliseconds (ms). This prolongation was similar to the QT prolongation caused by the drug moxifloxacin. In individuals with long QT syndrome, a smaller dose of grapefruit juice, 1.5 liters, resulted in a greater peak QTc prolongation of about 30 ms. The effect of smaller quantities of grapefruit juice on the QT interval is unclear.
Severity Major 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 something a lot of people don't realize about grapefruit: it can affect your heart's electrical timing, what we call the QT interval. Moxifloxacin already nudges that QT interval longer on its own. So when you pair the two, the effects can add up, and that's why this combo is flagged as a major concern.

In studies, large amounts of grapefruit juice (think liters, not a normal serving) stretched the QT about as much as moxifloxacin itself, and even more in people who already have long QT syndrome. A meaningfully longer QT can, in rare cases, trigger a dangerous irregular heartbeat. We're not certain a small glass matters, but I'd play it safe. Please check with your pharmacist or doctor before mixing grapefruit with this antibiotic, especially if you have any heart rhythm history.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chorin E, Hochstadt A, Granot Y, et al. Grapefruit juice prolongs the QT interval of healthy volunteers and patients with long QT syndrome. Heart Rhythm. 2019. pii: S1547-5271(19)30368-6. PubMed
Major

ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP)

2 of 2

Moxifloxacin also falls under ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP).

Grapefruit juice can decrease levels of drugs that are substrates of OATP.
In vitro and clinical research show that consuming grapefruit juice inhibits OATP, which reduces the bioavailability of oral drugs that are substrates of OATP. Various clinical studies have shown reduced absorption of OATP substrates when taken with grapefruit, including fexofenadine, acebutolol, aliskiren, celiprolol, levothyroxine, nadolol, and pitavastatin. Grapefruit juice is thought to affect OATP for only a short time. Therefore, separating drug administration and consumption of grapefruit by at least 4 hours is likely to prevent this interaction.
Severity Major Likelihood Likely Evidence B

Well-controlled human studies have demonstrated the likely existence of this interaction.

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

Here's the thing to know about pairing grapefruit with moxifloxacin (Avelox). Grapefruit briefly blocks a gut transporter called OATP that helps shuttle certain drugs into your bloodstream. When that transporter is slowed, less of the antibiotic gets absorbed, so your blood levels can drop. With an antibiotic, weaker levels are a real concern because you want a strong enough dose to fully knock out the infection. Falling short risks the bug not clearing or coming back.

The good news is this effect is short-lived. Spacing your grapefruit (or its juice) at least 4 hours away from your dose usually avoids the problem. While you're finishing an antibiotic course, I'd run your timing past your pharmacist or doctor first to be safe.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Greenblatt DJ. Analysis of drug interactions involving fruit beverages and organic anion-transporting polypeptides. J Clin Pharmacol 2009;49:1403-7. PubMed
  2. Bailey DG. Fruit juice inhibition of uptake transport: a new type of food-drug interaction. Br J Clin Pharmacol 2010;70:645-55. PubMed
  3. Lilja JJ, Raaska K, Neuvonen PJ. Effects of grapefruit juice on the pharmacokinetics of acebutolol. Br J Clin Pharmacol 2005;60:659-63. PubMed
  4. Ando, H., Tsuruoka, S., Yanagihara, H., Sugimoto, K., Miyata, M., Yamazoe, Y., Takamura, T., Kaneko, S., and Fujimura, A. Effects of grapefruit juice on the pharmacokinetics of pitavastatin and atorvastatin. Br J Clin Pharmacol 2005;60(5):494-497. DOI
  5. Lilja, J. J., Backman, J. T., Laitila, J., Luurila, H., and Neuvonen, P. J. Itraconazole increases but grapefruit juice greatly decreases plasma concentrations of celiprolol. Clin Pharmacol Ther 2003;73(3):192-198. PubMed
  6. Glaeser, H., Bailey, D. G., Dresser, G. K., Gregor, J. C., Schwarz, U. I., McGrath, J. S., Jolicoeur, E., Lee, W., Leake, B. F., Tirona, R. G., and Kim, R. B. Intestinal drug transporter expression and the impact of grapefruit juice in humans. Clin Pharma PubMed
  7. Lilja, J. J., Laitinen, K., and Neuvonen, P. J. Effects of grapefruit juice on the absorption of levothyroxine. Br J Clin Pharmacol 2005;60(3):337-341. PubMed
  8. Hu M, Mak VW, Yin OQ, Chu TT, Tomlinson B. Effects of grapefruit juice and SLCO1B1 388A>G polymorphism on the pharmacokinetics of pitavastatin. Drug Metab Pharmacokinet. 2013;28(2):104-8.
  9. Tanaka S, Uchida S, Miyakawa S, Inui N, Takeuchi K, Watanabe H, Namiki N. Comparison of inhibitory duration of grapefruit juice on organic anion-transporting polypeptide and cytochrome P450 3A4. Biol Pharm Bull. 2013;36(12):1936-41. PubMed
  10. Tapaninen T, Neuvonen PJ, Niemi M. Grapefruit juice greatly reduces the plasma concentrations of the OATP2B1 and CYP3A4 substrate aliskiren. Clin Pharmacol Ther. 2010 Sep;88(3):339-42. PubMed
  11. Piscitelli J, Nikanjam M, Capparelli EV, et al. Fexofenadine Plasma Concentrations to Estimate Systemic Exposure in Healthy Adults Using a Limited Sampling Strategy with a Population Pharmacokinetic Approach. Ther Drug Monit 2023;45(4):539-545. 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

Grapefruit Also Interacts With Other Medications

Grapefruit has 775 major, 151 moderate, 63 minor known drug interactions in our database — the Moxifloxacin one above is among them. If you take anything else, check it against the full list below.

Major 775 Moderate 151 Minor 63 No known interaction 1,841 (incl. Moxifloxacin)
Taking anything else?

Check Another of Your Medications Against Grapefruit

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

From our Q&A

Questions About Grapefruit or Moxifloxacin

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

This page covers Grapefruit only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Moxifloxacin page lists 155 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Apple (major), Arsenic (major) and Asarabacca (major).

By severity: 13 major · 121 moderate · 21 minor.

From our pharmacist’s overview on the Moxifloxacin page

“The supplement list for moxifloxacin (Avelox), a fluoroquinolone antibiotic, deserves genuine care, and the everyday items are the surprising part. Ordinary juices, apple, grapefruit, and sweet orange among them, block a transporter the drug needs for absorption and can cut how much reaches your blood, which for an antibiotic means the…”

Reviewed by 2 · Jul 18, 2026

Open the Moxifloxacin interaction page

One more smart check

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

We hold 1,144 real supplement products containing Grapefruit, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Grapefruit. Your product may carry other ingredients that interact with Moxifloxacin too, on top of Grapefruit — 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 Grapefruit and Moxifloxacin 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 Grapefruit
Top 10%

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

29 days ago today
Medication Moxifloxacin
Top 25%

#574 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 Grapefruit

What is Grapefruit?

Grapefruit
  • Source of vitamin C
  • Digestive complaints
  • Antimicrobial (seed extract)
  • Weight management
  • Skin and cosmetic uses

Grapefruit is a nutritious citrus fruit rich in vitamin C and other nutrients, and it is generally safe to eat. However, grapefruit is famous for serious interactions with many prescription medicines, so anyone taking medication should check with a pharmacist or doctor before consuming it regularly.

Read the full Grapefruit monograph & all interactions
Medication

About Moxifloxacin

What Is Moxifloxacin Used For?

Brand name: Avelox

Moxifloxacin tablets and intravenous (IV) injection are approved for adults 18 and older to treat bacterial infections including community-acquired pneumonia, uncomplicated and complicated skin infections, complicated abdominal infections, plague, acute bacterial sinusitis, and acute bacterial flare-ups of chronic bronchitis. Note: moxifloxacin should only be used for sinusitis and chronic bronchitis flare-ups when no other antibiotic option is available, due to the risk of serious side effects.

Moxifloxacin ophthalmic solution (eye drops) — including the brand Vigamox — is a separate, topical formulation used only in the eye to treat bacterial conjunctivitis (pink eye) caused by susceptible bacteria. The eye drop form is not used for body-wide infections.

See full Moxifloxacin drug information
Keep checking

Other Drugs & Grapefruit

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

775Major
151Moderate
63Minor
1,840No known interaction
775 Major 151 Moderate 63 Minor 1,840 No interaction
Major

775 interactions

Showing 60 of 775 major interactions — see all 775 on the Grapefruit page.

Moderate

151 interactions

Showing 60 of 151 moderate interactions — see all 151 on the Grapefruit page.

Minor

63 interactions

Showing 60 of 63 minor interactions — see all 63 on the Grapefruit page.

No interaction 1,840 drugs checked — show the list

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

Showing the 60 most looked-up of 1,840 medications checked with no known interaction — see the full Grapefruit list.

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

Can you take Grapefruit with Moxifloxacin?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Grapefruit and Moxifloxacin?
Moxifloxacin belongs to more than one drug category, and Grapefruit interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Grapefruit and Moxifloxacin interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Moxifloxacin and Grapefruit?

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.