Drug & supplement interaction

Guarana + Chlorothiazide, Methyldopa

Chlorothiazide, Methyldopa brand names: Aldoclor 150, Aldochlor, Aldoclor 250.

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

Guarana has a moderate interaction with Chlorothiazide, Methyldopa. Theoretically, using guarana with diuretic drugs might increase the risk of hypokalemia.

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

Guarana and Chlorothiazide, Methyldopa

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

Moderate

DIURETIC DRUGS

Why this applies to Chlorothiazide, Methyldopa

Chlorothiazide, Methyldopa falls under DIURETIC DRUGS — the group Guarana interacts with.

Theoretically, using guarana with diuretic drugs might increase the risk of hypokalemia.
Guarana contains caffeine. Caffeine, especially in excessive amounts, can reduce potassium levels due to stimulation of the sodium-potassium pump. Diuretics can also lower potassium levels.
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

Your medication pairs methyldopa with chlorothiazide, and chlorothiazide is a thiazide-type water pill. One thing thiazides are known for is lowering potassium in your blood over time. Here's where guarana comes in: it's basically loaded with caffeine, and a lot of caffeine can nudge potassium down too. So the worry is that the two together could push your potassium a little lower than either one alone.

I want to be honest that this is a theoretical concern based on how the two work, not something proven in studies, and a cup or two of a guarana drink probably won't matter much. But low potassium can cause muscle cramps, weakness, or an off-feeling heartbeat. If you take concentrated guarana supplements regularly, mention it to your pharmacist or doctor so they can keep an eye on your potassium.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Norager, C. B., Jensen, M. B., Weimann, A., and Madsen, M. R. Metabolic effects of caffeine ingestion and physical work in 75-year old citizens. A randomized, double-blind, placebo-controlled, cross-over study. Clin Endocrinol (Oxf) 2006;65(2):223-228. PubMed
  2. Simmonds, M. J., Minahan, C. L., and Sabapathy, S. Caffeine improves supramaximal cycling but not the rate of anaerobic energy release. Eur.J Appl Physiol 2010;109(2):287-295. PubMed
  3. Rigato, I., Blarasin, L., and Kette, F. Severe hypokalemia in 2 young bicycle riders due to massive caffeine intake. Clin J Sport Med. 2010;20(2):128-130. PubMed
  4. Ernest, D., Chia, M., and Corallo, C. E. Profound hypokalaemia due to Nurofen Plus and Red Bull misuse. Crit Care Resusc. 2010;12(2):109-110. DOI
  5. Clausen, T. Hormonal and pharmacological modification of plasma potassium homeostasis. Fundam.Clin Pharmacol 2010;24(5):595-605. 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

Guarana Also Interacts With Other Medications

Guarana has 8 major, 461 moderate, 185 minor known drug interactions in our database — the Chlorothiazide, Methyldopa one above is one of them. If you take anything else, check it against the full list below.

Major 8 Moderate 461 Minor 185 No known interaction 2,176 (incl. Chlorothiazide, Methyldopa)
Taking anything else?

Check Another of Your Medications Against Guarana

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

Everything else you take

See Every Supplement That Interacts With Chlorothiazide, Methyldopa

This page covers Guarana only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Chlorothiazide, Methyldopa page lists 258 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 Beer (major).

By severity: 13 major · 220 moderate · 25 minor.

From our pharmacist’s overview on the Chlorothiazide, Methyldopa page

“Aldoclor pairs chlorothiazide, a water pill, with methyldopa, an older blood pressure medicine, and its supplement list is one to treat with genuine care. Thirteen of the 258 ingredients on file are rated major, and most of the remaining 220 moderate and 25 minor entries do one of two things: drop blood pressure lower than intended, or…”

Reviewed by 2 · Jul 18, 2026

Open the Chlorothiazide, Methyldopa interaction page

One more smart check

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

We hold 1,430 real supplement products containing Guarana, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Guarana. Your product may carry other ingredients that interact with Chlorothiazide, Methyldopa too, on top of Guarana — 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 Guarana and Chlorothiazide, Methyldopa 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 Guarana
Top 10%

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

29 days ago today
Medication Chlorothiazide, Methyldopa
Steady interest

#2,286 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 Guarana

What is Guarana?

Guarana
  • Energy and alertness
  • Reducing fatigue
  • Weight loss support
  • Athletic performance
  • Mental focus

Guarana is an Amazonian seed that is naturally high in caffeine, which explains most of its stimulant and energy effects. While it may give a short-term boost in alertness and reduce fatigue, strong evidence for weight loss or major performance gains is limited, and it carries the same risks as too much caffeine. Talk to your pharmacist or doctor before using it, especially if you have heart problems, anxiety, or are pregnant.

Read the full Guarana monograph & all interactions
Keep checking

Other Drugs & Guarana

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

8Major
461Moderate
185Minor
2,175No known interaction
8 Major 461 Moderate 185 Minor 2,175 No interaction
Major

8 interactions

Moderate

461 interactions

Showing 60 of 461 moderate interactions — see all 461 on the Guarana page.

Minor

185 interactions

Showing 60 of 185 minor interactions — see all 185 on the Guarana page.

No interaction 2,175 drugs checked — show the list

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

Showing the 60 most looked-up of 2,175 medications checked with no known interaction — see the full Guarana list.

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

Can you take Guarana with Chlorothiazide, Methyldopa?
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 Guarana and Chlorothiazide, Methyldopa 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

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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.