Drug & supplement interaction

Vitamin E + Ritonavir

Ritonavir brand name: Norvir.

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

Vitamin E has a moderate interaction with Ritonavir. Theoretically, vitamin E might induce metabolism of CYP3A4, possibly reducing the levels CYP3A4 substrates.

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

Vitamin E and Ritonavir

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

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Why this applies to Ritonavir

Ritonavir falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Vitamin E interacts with.

Theoretically, vitamin E might induce metabolism of CYP3A4, possibly reducing the levels CYP3A4 substrates.
Vitamin E appears to bind with the nuclear receptor, pregnane X receptor (PXR), which results in increased expression of CYP3A4. Although the clinical significance of this is not known, use caution when considering concomitant use of vitamin E and other drugs affected by these enzymes.
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 ritonavir (Norvir) and vitamin E. The concern on file is that vitamin E might gently nudge a liver enzyme called CYP3A4 to work faster. Since ritonavir is broken down by that same enzyme, speeding it up could in theory lower the amount of ritonavir in your blood. With an HIV medication, weaker levels are the worry, because you want it working hard to keep the virus suppressed.

The honest part: this is theoretical, based on how the chemistry should behave, not on real patient outcomes. Everyday food amounts of vitamin E are very unlikely to matter. High-dose supplements are the real question mark. Don't stop or change anything on your own. Just check with your pharmacist or HIV provider before adding a vitamin E supplement so they can keep your treatment on track.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Landes N, Pfluger P, Kluth D, et al. Vitamin E activates gene expression via the pregnane X receptor. Biochem Pharmacol 2003;65:269-73. . PubMed
  2. Brigelius-Flohe R. Vitamin E and drug metabolism. Biochem Biophys Res Commun 2003;305:737-40. 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

Vitamin E Also Interacts With Other Medications

Vitamin E has 762 moderate, 1 minor known drug interactions in our database — the Ritonavir one above is one of them. If you take anything else, check it against the full list below.

Moderate 762 Minor 1 No known interaction 2,067 (incl. Ritonavir)
Taking anything else?

Check Another of Your Medications Against Vitamin E

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

From our Q&A

Questions About Vitamin E or Ritonavir

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

This page covers Vitamin E only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Ritonavir page lists 178 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 136 moderate · 36 minor.

From our pharmacist’s overview on the Ritonavir page

“If you take ritonavir (Norvir), slow down before adding any supplement from this page. Six of the 178 ingredients here carry a major rating, and St.”

Reviewed by 2 · Jul 18, 2026

Open the Ritonavir interaction page

One more smart check

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

We hold 22,182 real supplement products containing Vitamin E, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Vitamin E. Your product may carry other ingredients that interact with Ritonavir too, on top of Vitamin E — 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 Vitamin E and Ritonavir 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 Vitamin E
Top 10

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

29 days ago today
Medication Ritonavir
Steady interest

#2,786 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 Vitamin E

What is Vitamin E?

Vitamin E
  • General antioxidant support
  • Skin and hair care
  • Heart health
  • Eye health (age-related conditions)
  • Immune support

Vitamin E is an essential fat-soluble vitamin and antioxidant that most people get in adequate amounts from a normal diet. Supplements can help correct a true deficiency, but high-dose vitamin E has not been clearly proven to prevent heart disease or cancer and may carry risks. Talk to your pharmacist or doctor before taking high doses.

Read the full Vitamin E monograph & all interactions
Medication

About Ritonavir

What Is Ritonavir Used For?

Brand name: Norvir

Ritonavir (brand name Norvir) is used together with other HIV medicines to treat HIV-1 infection in adults and children older than one month of age. It is always taken as part of a combination regimen — never on its own.

Norvir oral powder is specifically indicated for pediatric patients with HIV-1 infection. Norvir tablets and oral solution are indicated for both adults and pediatric patients with HIV-1 infection. Ritonavir tablets (generic) are also indicated for the treatment of HIV-1 infection in combination with other antiretroviral agents.

See full Ritonavir drug information
Keep checking

Other Drugs & Vitamin E

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

0Major
762Moderate
1Minor
2,066No known interaction
762 Moderate 1 Minor 2,066 No interaction
Moderate

762 interactions

Showing 60 of 762 moderate interactions — see all 762 on the Vitamin E page.

Minor

1 interaction

No interaction 2,066 drugs checked — show the list

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

Showing the 60 most looked-up of 2,066 medications checked with no known interaction — see the full Vitamin E list.

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

Can you take Vitamin E with Ritonavir?
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 Vitamin E and Ritonavir 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 Ritonavir and Vitamin E?

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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.