Drug & supplement interaction

Coffee Charcoal + Iohexol

Iohexol brand names: Omnipaque, Oraltag.

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

Coffee Charcoal has a moderate interaction with Iohexol. Coffee charcoal can reduce the absorption of orally administered drugs and should be separated from oral drug administration by at least two hours.

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

Coffee Charcoal and Iohexol

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

Moderate

ORAL DRUGS

Why this applies to Iohexol

Iohexol falls under ORAL DRUGS — the group Coffee Charcoal interacts with.

Coffee charcoal can reduce the absorption of orally administered drugs and should be separated from oral drug administration by at least two hours.
Severity Moderate Likelihood Probable Evidence D

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 picture. Coffee charcoal has a porous, sponge-like surface, so when it's sitting in your gut it can grab onto other substances and keep them from being absorbed. Oraltag is the oral form of iohexol, a contrast agent you swallow before a CT scan so your doctor can see your digestive tract clearly. If charcoal binds up the iohexol, less of it coats your gut, and that can leave you with a blurry or less useful scan.

This is a theoretical concern based on how charcoal behaves, not a documented disaster, but it makes sense to play it safe. The simple fix is timing: keep coffee charcoal and your oral iohexol dose at least a couple of hours apart, and let the team doing your scan know what you're taking. When in doubt, check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.

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

Coffee Charcoal Also Interacts With Other Medications

Coffee Charcoal has 2,021 moderate known drug interactions in our database — the Iohexol one above is one of them. If you take anything else, check it against the full list below.

Moderate 2,021 No known interaction 809 (incl. Iohexol)
Taking anything else?

Check Another of Your Medications Against Coffee Charcoal

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

Everything else you take

See Every Supplement That Interacts With Iohexol

This page covers Coffee Charcoal only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Iohexol page lists 23 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Biofeedback (moderate), Dendrobium (moderate), European Mandrake (moderate) and Ginkgo (moderate).

By severity: 1 major · 13 moderate · 9 minor.

From our pharmacist’s overview on the Iohexol page

“Iohexol (Omnipaque, Oraltag) is a contrast dye used to sharpen CT scans and other imaging, and its supplement list deserves genuine attention before an appointment. Of the 23 ingredients on file, 17 can change how drugs taken by mouth get absorbed, which matters most with the oral form, Oraltag, since altered absorption can muddy the s…”

Reviewed by 2 · Jul 18, 2026

Open the Iohexol interaction page

How much people look this up

Where Coffee Charcoal and Iohexol 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 Coffee Charcoal
Top half

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

29 days ago today
Medication Iohexol
Top half

#1,072 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 Coffee Charcoal

What is Coffee Charcoal?

  • Diarrhea
  • Inflammatory bowel conditions
  • Irritable bowel syndrome (IBS)
  • Mild digestive upset
  • Wound and skin care (topical, traditional)

Coffee charcoal is made by roasting green coffee beans until they turn black, creating a charcoal-like material used traditionally for diarrhea and digestive complaints. Scientific evidence supporting its benefits is very limited, and it should not replace proven treatments. Talk with your pharmacist or doctor before using it, especially if you have a chronic gut condition.

Read the full Coffee Charcoal monograph & all interactions
Keep checking

Other Drugs & Coffee Charcoal

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

0Major
2,021Moderate
0Minor
808No known interaction
2,021 Moderate 808 No interaction
Moderate

2,021 interactions

Showing 60 of 2,021 moderate interactions — see all 2,021 on the Coffee Charcoal page.

No interaction 808 drugs checked — show the list

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

Showing the 60 most looked-up of 808 medications checked with no known interaction — see the full Coffee Charcoal list.

See the full Coffee Charcoal interactions page
See every supplement checked against Iohexol, 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
Coffee Charcoal monograph › Uses, safety, and every drug interaction in one place Iohexol supplement interactions › Every supplement checked against Iohexol, 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 Coffee Charcoal and Iohexol Together: Common Questions

Can you take Coffee Charcoal with Iohexol?
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 Coffee Charcoal and Iohexol 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 Iohexol and Coffee Charcoal?

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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.