Drug & supplement interaction

Grapefruit Diet + Zanamivir

Zanamivir brand name: Relenza.

No Known Interaction

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated June 2026 · Pair last verified Sep 27, 2026

The bottom line No known interaction

We found no known interaction between Grapefruit Diet and Zanamivir in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first.

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Interaction report

Grapefruit Diet and Zanamivir

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Zanamivir and Grapefruit Diet in our sources. This does not guarantee that the combination is completely free of risk — research on Grapefruit Diet alongside specific medications may be limited.

Worth understanding: our licensed dataset holds no drug-interaction record for Grapefruit Diet at all — not against Zanamivir, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

Grapefruit Diet is an eating pattern rather than something you take. Ask your pharmacist or doctor before changing how you eat while on a prescribed medicine: some medicines are dosed around meals, and a change in diet can change how they work. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Grapefruit Diet safety at a glance

Grapefruit Diet overall Use caution Grapefruit is a healthy food, but very low-calorie versions of this diet can be hard to sustain and grapefruit affects many medications.

Pregnancy Use caution Eating grapefruit as food is generally fine, but very low-calorie diets should be avoided during pregnancy.

Breastfeeding Use caution Grapefruit as food is usually fine, but restrictive dieting while breastfeeding is not recommended.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Zanamivir and Grapefruit Diet? Ask Dr. Brian Staiger, PharmD, BCPS directly ›

What to actually watch for

What Zanamivir’s Own FDA Label Lists

This is not an interaction — none of it involves Grapefruit Diet. These are the most notable effects listed in the ADVERSE REACTIONS section of Zanamivir’s own FDA label, for the medication by itself. Knowing the drug’s own list makes it easier to work out the likely cause if something new turns up while you follow Grapefruit Diet and take the medicine. 2 of them are worth acting on rather than waiting out — marked below.

Wheezing Worth acting on
A higher chance of infection Worth acting on
Chills
Cough
Joint pain
Fever
Dizziness
Diarrhea
Vomiting
Headache

Showing the 10 most notable of 11 label-listed effects — ranked by how unusual each one is across medicines generally, with serious effects weighted up.

From the ADVERSE REACTIONS section of the FDA label for Zanamivir. Read the label on DailyMed › Grapefruit Diet’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Grapefruit Diet side to compare — that is a limit of the record, not a statement that Grapefruit Diet has no side effects.

Everything else you take

See Every Supplement That Interacts With Zanamivir

This page covers Grapefruit Diet only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Zanamivir page lists 17 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Coffee Charcoal (moderate), European Mandrake (moderate), Glucomannan (moderate) and Guar Gum (moderate).

By severity: 1 major · 7 moderate · 9 minor.

From our pharmacist’s overview on the Zanamivir page

“Activated charcoal is the single entry I would want anyone on zanamivir (Relenza) to understand first. It holds the one major rating among the 17 supplements known to interact, because charcoal binds many drugs and can lower how much reaches the body, even when a medicine is not swallowed.”

Reviewed by 2 · Jul 18, 2026

Open the Zanamivir interaction page

How much people look this up

Where Grapefruit Diet and Zanamivir 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 Diet

Steady interest

#1,057 of 1,452 supplements looked up here in the last 7 days

29 days ago today

Medication Zanamivir

Steady interest

#2,128 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.

Where does our data come from?

Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions. Grapefruit Diet is not yet covered by that licensed database, so its write-up cites publicly available medical sources directly (see the references below).
Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Grapefruit Diet reference on this page ↓
Freshness: we automatically re-check this combination every week — this pair was last verified September 27, 2026. The Grapefruit Diet and Zanamivir records this page draws on were last updated June 22, 2026.
What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.

Data structure & sourcing designed and verified by Dr. Brian Staiger, PharmD, BCPS.

Eating pattern

About Grapefruit Diet

What is Grapefruit Diet?

Weight loss
Appetite control
Short-term dieting
Blood sugar support
General 'detox' plans

The 'Grapefruit Diet' is a fad eating plan that pairs grapefruit or grapefruit juice with low-calorie meals, claiming the fruit burns fat. Any weight loss is most likely from cutting calories rather than a special fat-burning property of grapefruit. Grapefruit interacts with many medications, so talk to your pharmacist or doctor before starting.

Fruit and fruit juice (Citrus paradisi) · Fresh grapefruit, grapefruit juice, and as part of structured low-calorie meal plans; also grapefruit extract capsules sometimes marketed for weight loss

An interaction check asks whether these two react with each other — it does not ask whether Grapefruit Diet is a good idea for someone in your situation. Here is what our Grapefruit Diet record says about it on its own.

Grapefruit Diet: dosing

There is no standardized or medically established dose for the Grapefruit Diet. Plans typically suggest eating half a grapefruit or drinking a small glass of grapefruit juice with meals, but these amounts vary by version and are not based on solid research.If you choose to add grapefruit to your diet, a reasonable, food-based approach is far safer than a strict, very low-calorie plan.

From our Grapefruit Diet monograph — the full record covers uses, side effects and every documented interaction.

Read the full Grapefruit Diet monograph & all interactions

Medication

About Zanamivir Oral Inhalation

What Is Zanamivir Oral Inhalation Used For?

Brand name: Relenza

Relenza (zanamivir) inhalation powder is used to treat uncomplicated, acute influenza A and B in adults and children aged 7 and older — but only when symptoms have been present for no more than 2 days. The sooner treatment starts, the better.

Relenza is also used to help prevent (prophylax) influenza in adults and children aged 5 and older, including in household settings where someone is sick and in broader community outbreaks. It is not a substitute for your annual flu vaccine, and it has not been shown to prevent influenza in nursing home residents.

Most-Reported Side Effects for Zanamivir

From FAERS, the FDA’s public side-effect reporting system (2,524 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Abnormal behaviour 398 reports

Overdose 395 reports

Drug exposure during pregnancy 244 reports

Hallucination 159 reports

Drug exposure via breast milk 123 reports

See full Zanamivir Oral Inhalation drug information

Keep checking

Other Drugs & Grapefruit Diet

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

0Major

0Moderate

0Minor

2,829No known interaction

2,829 No interaction

No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Grapefruit Diet list.

See the full Grapefruit Diet interactions page

See every supplement checked against Zanamivir, ranked by severity

Evidence & sources

Grapefruit Diet References

The 2 sources that drive our Grapefruit Diet monograph — publicly available pages from reputable medical and government organizations. Every link was verified to work before publishing. Grapefruit Diet is not covered by the licensed Natural Medicines interaction database, so its page cites these public sources directly.

Grapefruit — MedlinePlus Source
Choosing a Safe and Successful Weight-Loss Program — NIH NIDDK Source

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Following Grapefruit Diet While Taking Zanamivir: Common Questions

Is it safe to follow Grapefruit Diet while taking Zanamivir?

We do not list a known interaction between Grapefruit Diet and Zanamivir. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.

Does Zanamivir interact with any supplements?

Yes. Zanamivir has documented interactions with 17 supplements in our database — Grapefruit Diet is not one of them. The Zanamivir interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Grapefruit Diet monograph Uses, safety profile, and every drug interaction in one place Zanamivir Oral Inhalation drug information The full plain-English guide to this medication Zanamivir supplement interactions Every supplement checked against Zanamivir, 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 References The 2 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Zanamivir and Grapefruit Diet?

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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.