Drug & supplement interaction

Chlorella + Hydrochlorothiazide, Metoprolol

Hydrochlorothiazide, Metoprolol brand name: Lopressor HCT.

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

Chlorella has a moderate interaction with Hydrochlorothiazide, Metoprolol. Theoretically, chlorella might have additive effects with photosensitizing drugs.

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

Chlorella and Hydrochlorothiazide, Metoprolol

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

Moderate

PHOTOSENSITIZING DRUGS

Why this applies to Hydrochlorothiazide, Metoprolol

Hydrochlorothiazide, Metoprolol falls under PHOTOSENSITIZING DRUGS — the group Chlorella interacts with.

Theoretically, chlorella might have additive effects with photosensitizing drugs.
Chlorella has been reported to cause photosensitization. In five case reports, patients who had ingested chlorella exhibited swelling followed by erythematopurpuric lesions on sun-exposed areas of the body. Theoretically, concomitant use with photosensitizing drugs may exacerbate effects.
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 for your Lopressor HCT (that's hydrochlorothiazide plus metoprolol). The hydrochlorothiazide part is a water pill that can make your skin more sensitive to sunlight, so you may sunburn faster than usual. Chlorella has been linked, in a handful of case reports, to a similar sun-sensitivity reaction (swelling and reddish-purple spots on areas the sun hits). Put them together and, in theory, you could be a little more prone to sunburn or a skin rash.

This is a theoretical concern based on how each behaves, not something proven to happen often, so don't panic. Just be smart in the sun: use sunscreen, wear a hat, and cover up. If you notice an unusual rash, check in with your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Peirce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York, NY: William Morrow and Co., 1999.
  2. Jitsukawa K, Suizu R, Hidano A. Chlorella photosensitization. New phytophotodermatosis. Int J Dermatol 1984;23:263-8. 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

Chlorella Also Interacts With Other Medications

Chlorella has 336 moderate known drug interactions in our database — the Hydrochlorothiazide, Metoprolol one above is one of them. If you take anything else, check it against the full list below.

Moderate 336 No known interaction 2,494 (incl. Hydrochlorothiazide, Metoprolol)
Taking anything else?

Check Another of Your Medications Against Chlorella

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

From our Q&A

Questions About Chlorella or Hydrochlorothiazide, Metoprolol

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

This page covers Chlorella only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Hydrochlorothiazide, Metoprolol page lists 276 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Asarabacca (major) and Dolomite (major).

By severity: 11 major · 235 moderate · 30 minor.

From our pharmacist’s overview on the Hydrochlorothiazide, Metoprolol page

“I would treat this list with genuine care. Lopressor HCT combines hydrochlorothiazide, a diuretic, with metoprolol, a beta-blocker, and 276 supplement and herbal ingredients interact with the pair, 11 of them rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Hydrochlorothiazide, Metoprolol interaction page

One more smart check

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

We hold 3,341 real supplement products containing Chlorella, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Chlorella. Your product may carry other ingredients that interact with Hydrochlorothiazide, Metoprolol too, on top of Chlorella — 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 Chlorella and Hydrochlorothiazide, Metoprolol 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 Chlorella
Top 10%

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

29 days ago today
Medication Hydrochlorothiazide, Metoprolol
Top 25%

#626 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 Chlorella

What is Chlorella?

Chlorella
  • General nutrition and 'detox' support
  • Immune support
  • Liver and kidney support
  • Antioxidant and anti-inflammatory support
  • Cholesterol and heart health

Chlorella is a nutrient-rich freshwater green algae taken as a supplement for general wellness, immune support, and 'detox.' Some small studies suggest possible benefits for cholesterol, blood pressure, and immune markers, but the overall evidence is limited and not strong. It is generally well tolerated, but quality varies and it should be avoided during pregnancy and breastfeeding unless a doctor approves.

Read the full Chlorella monograph & all interactions
Keep checking

Other Drugs & Chlorella

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

0Major
336Moderate
0Minor
2,493No known interaction
336 Moderate 2,493 No interaction
Moderate

336 interactions

Showing 60 of 336 moderate interactions — see all 336 on the Chlorella page.

No interaction 2,493 drugs checked — show the list

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

Showing the 60 most looked-up of 2,493 medications checked with no known interaction — see the full Chlorella list.

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

Can you take Chlorella with Hydrochlorothiazide, Metoprolol?
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 Chlorella and Hydrochlorothiazide, Metoprolol 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 Hydrochlorothiazide, Metoprolol and Chlorella?

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.