Drug & supplement interaction

Agar + Retinol

Retinol brand name: Aquasol A.

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

Agar has a minor interaction with Retinol. Agar forms a thick gel, which may disrupt the absorption of nutrients and medications.

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

Agar and Retinol

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

Minor

ORAL DRUGS

Why this applies to Retinol

Retinol falls under ORAL DRUGS — the group Agar interacts with.

Agar forms a thick gel, which may disrupt the absorption of nutrients and medications. Animal research suggests that consuming a diet consisting of 5% to 10% agar alters the absorption of nutrients from the diet. In one study, consuming a diet composed of 10% agar reduced the absorption of all evaluated minerals. Theoretically, agar may also impair the absorption of oral drugs.
Severity Minor 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 simple version: agar swells into a thick gel in your gut, and that gel can grab onto things passing through, including fat-soluble vitamins like the vitamin A in your Aquasol A. If they're sitting in your stomach at the same time, the agar could slightly reduce how much vitamin A you actually absorb. So instead of your levels building up, you might get a little less benefit from the dose you took.

Honestly, this is a theoretical concern based mostly on animal studies, and it's rated as minor. To play it safe, just don't take your vitamin A right alongside an agar supplement. Spacing them by a couple of hours is usually plenty. If you're taking vitamin A to correct a real deficiency, mention the agar to your pharmacist so they can keep an eye on things.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  2. Kondo H, Osada A. Influence of dietary fiber on the bioavailability of zinc in rats. Biomed Environ Sci. 1996 Sept;9(2-3):204-8.
  3. Harmuth-Hoene, A. E. and Schelenz, R. Effect of dietary fiber on mineral absorption in growing rats. J Nutr 1980;110(9):1774-1784. 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

Agar Also Interacts With Other Medications

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

Minor 2,021 No known interaction 809 (incl. Retinol)
Taking anything else?

Check Another of Your Medications Against Agar

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

From our Q&A

Questions About Agar or Retinol

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

This page covers Agar only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Retinol page lists 28 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), African Wild Potato (moderate), Breadfruit (moderate), Cannabidiol (cbd) (moderate) and Coffee Charcoal (moderate).

By severity: 1 major · 16 moderate · 11 minor.

From our pharmacist’s overview on the Retinol page

“Activated charcoal is the one interaction here rated major, and it deserves attention first. It binds drugs in the gut and can pull retinol (Aquasol A, prescription vitamin A) out of your system, cutting how much actually stays in circulation.”

Reviewed by 2 · Jul 18, 2026

Open the Retinol interaction page

One more smart check

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

We hold 23 real supplement products containing Agar, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Agar. Your product may carry other ingredients that interact with Retinol too, on top of Agar — 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 Agar and Retinol 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 Agar
Top half

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

29 days ago today
Medication Retinol
Steady interest

#2,450 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 Agar

What is Agar?

Agar
  • Constipation
  • Weight loss
  • Vegetarian gelatin substitute
  • Source of dietary fiber
  • Appetite control

Agar is a plant-based gel made from red seaweed that is widely used as a vegetarian alternative to gelatin and as a source of dietary fiber. It is sometimes taken as a bulk-forming laxative or weight-loss aid, but solid human evidence for these health uses is limited. It is generally considered safe as a food, but you should drink plenty of water with it and check with your pharmacist before using it as a supplement.

Read the full Agar monograph & all interactions
Medication

About Vitamin A

What Is Vitamin A Used For?

Brand name: Aquasol A

Vitamin A is used to treat vitamin A deficiency. Aquasol A (intramuscular injection) is specifically indicated when a person cannot take vitamin A by mouth — for example, due to nausea, vomiting, loss of appetite, or a condition that prevents the gut from absorbing nutrients properly (malabsorption syndrome).

Vitamin A D ointment is a topical product used on the skin to help treat chafed skin from diaper rash, temporarily protect minor cuts, scrapes, and burns, and relieve chapped or cracked skin and lips. It also helps protect skin from drying effects of wind and cold weather.

See full Vitamin A drug information
Keep checking

Other Drugs & Agar

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

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

2,021 interactions

Showing 60 of 2,021 minor interactions — see all 2,021 on the Agar page.

No interaction 808 drugs checked — show the list

We also checked Agar 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 Agar list.

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

Can you take Agar with Retinol?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Agar and Retinol interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Retinol and Agar?

Our pharmacists answer your medication & supplement questions — free.

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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.