Drug & supplement interaction

Rooibos + Dextromethorphan, Guaifenesin

Dextromethorphan, Guaifenesin brand names: Sudal DM, Touro DM, Queltuss, Fenesin DM, Monafed DM, and others.

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

Dextromethorphan, Guaifenesin falls into 2 drug categories that Rooibos can interact with; the most serious is rated moderate. Theoretically, taking rooibos with CYP2D6 substrates may increase the effects of CYP2D6 substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Rooibos and Dextromethorphan, Guaifenesin

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

Why Are There 2 Interactions?

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

Moderate

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

1 of 2

Why this applies to Dextromethorphan, Guaifenesin

Dextromethorphan, Guaifenesin falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES — the group Rooibos interacts with.

Theoretically, taking rooibos with CYP2D6 substrates may increase the effects of CYP2D6 substrates.
In vitro research shows that the methanol extract of rooibos leaves and stems inhibits CYP2D6 enzyme activity.
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 your cough and chest medicine: the dextromethorphan part is cleared from your body by a liver enzyme called CYP2D6. In test-tube studies, a concentrated rooibos extract slowed that enzyme down a bit. If that happened in real life, dextromethorphan could linger and build up, which might mean more drowsiness, dizziness, or feeling foggy. The guaifenesin piece isn't really affected here.

Now, the important part: this is only lab data, not something proven in people, and a normal cup of rooibos tea is very unlikely to cause trouble. Concentrated extracts are the bigger question mark. If you take rooibos pills regularly, just run it by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Fantoukh OI, Dale OR, Parveen A, et al. Safety Assessment of Phytochemicals Derived from the Globalized South African Rooibos Tea (Aspalathus linearis) through Interaction with CYP, PXR, and P-gp. J Agric Food Chem. 2019;67(17):4967-4975.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Dextromethorphan, Guaifenesin also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, taking rooibos with CYP3A4 substrates may increase the effects of CYP3A4 substrates.
In vitro research shows that the methanol extract of rooibos leaves and stems strongly inhibits CYP3A4 enzyme activity.
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 your cough and congestion combo. One part of it, dextromethorphan, is partly cleared by a liver enzyme called CYP3A4. In a lab dish, concentrated rooibos extract slowed that enzyme down. If that happened in your body, a bit more dextromethorphan could linger, which might mean more drowsiness, dizziness, or a foggy feeling. The guaifenesin half isn't really affected.

Now the reassuring part: this is only test-tube evidence, not something seen in people, and a normal mug of rooibos tea is very unlikely to cause trouble. Concentrated rooibos capsules or extracts are the bigger question mark. If you use those regularly, just check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Fantoukh OI, Dale OR, Parveen A, et al. Safety Assessment of Phytochemicals Derived from the Globalized South African Rooibos Tea (Aspalathus linearis) through Interaction with CYP, PXR, and P-gp. J Agric Food Chem. 2019;67(17):4967-4975.

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

Rooibos Also Interacts With Other Medications

Rooibos has 878 moderate known drug interactions in our database — the Dextromethorphan, Guaifenesin one above is among them. If you take anything else, check it against the full list below.

Moderate 878 No known interaction 1,952 (incl. Dextromethorphan, Guaifenesin)
Taking anything else?

Check Another of Your Medications Against Rooibos

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

Everything else you take

See Every Supplement That Interacts With Dextromethorphan, Guaifenesin

This page covers Rooibos only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Dextromethorphan, Guaifenesin page lists 171 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), Lithium (major), St. John's Wort (major) and 1,3-dmaa (moderate).

By severity: 4 major · 125 moderate · 42 minor.

From our pharmacist’s overview on the Dextromethorphan, Guaifenesin page

“Dextromethorphan with guaifenesin (Sudal DM, Touro DM, Queltuss, and others) sounds too ordinary a cough medicine to tangle badly with supplements, yet 4 of the 171 ingredients on this list rate major and belong at the top of your reading. Grapefruit and St.”

Reviewed by 2 · Jul 18, 2026

Open the Dextromethorphan, Guaifenesin interaction page

One more smart check

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

We hold 142 real supplement products containing Rooibos, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Rooibos. Your product may carry other ingredients that interact with Dextromethorphan, Guaifenesin too, on top of Rooibos — 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 Rooibos and Dextromethorphan, Guaifenesin 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 Rooibos
Top half

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

29 days ago today
Medication Dextromethorphan, Guaifenesin
Steady interest

#2,319 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 Rooibos

What is Rooibos?

Rooibos
  • Caffeine-free beverage
  • Antioxidant support
  • Heart health
  • Blood sugar support
  • Digestive upset
  • General wellness

Rooibos is a caffeine-free herbal tea from South Africa that is rich in antioxidants and generally considered safe as a beverage. While lab and early studies suggest possible benefits for heart health, blood sugar, and inflammation, strong human evidence is lacking for most medical uses. Enjoy it as a tea, but talk to your pharmacist or doctor before using concentrated extracts for health reasons.

Read the full Rooibos monograph & all interactions
Keep checking

Other Drugs & Rooibos

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

0Major
878Moderate
0Minor
1,951No known interaction
878 Moderate 1,951 No interaction
Moderate

878 interactions

Showing 60 of 878 moderate interactions — see all 878 on the Rooibos page.

No interaction 1,951 drugs checked — show the list

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

Showing the 60 most looked-up of 1,951 medications checked with no known interaction — see the full Rooibos list.

See the full Rooibos interactions page
See every supplement checked against Dextromethorphan, Guaifenesin, 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
Rooibos monograph › Uses, safety, and every drug interaction in one place Dextromethorphan, Guaifenesin supplement interactions › Every supplement checked against Dextromethorphan, Guaifenesin, 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 Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Rooibos and Dextromethorphan, Guaifenesin Together: Common Questions

Can you take Rooibos with Dextromethorphan, Guaifenesin?
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.
Why are there 2 interactions listed for Rooibos and Dextromethorphan, Guaifenesin?
Dextromethorphan, Guaifenesin belongs to more than one drug category, and Rooibos 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 Rooibos and Dextromethorphan, Guaifenesin 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 Dextromethorphan, Guaifenesin and Rooibos?

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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.