Drug & supplement interaction

Soy + Cyclothiazide

Cyclothiazide brand names: Fluidil, Anhydron.

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

Cyclothiazide falls into 2 drug categories that Soy can interact with; the most serious is rated moderate. Theoretically soy protein may have additive effects with antihypertensive drugs and increase the risk of hypotension.

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

Soy and Cyclothiazide

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

Why Are There 2 Interactions?

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

Moderate

ANTIHYPERTENSIVE DRUGS

1 of 2

Why this applies to Cyclothiazide

Cyclothiazide falls under ANTIHYPERTENSIVE DRUGS — the group Soy interacts with.

Theoretically soy protein may have additive effects with antihypertensive drugs and increase the risk of hypotension.
Although some contradictory research exists, most clinical evidence suggests that consuming soy protein modestly reduces systolic and diastolic blood pressure in individuals with prehypertension or hypertension.
Severity Moderate Likelihood Possible Evidence A

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

Cyclothiazide is a thiazide-type water pill that lowers blood pressure and helps your body get rid of extra fluid. Here's the thing with soy: research suggests that soy protein can itself nudge blood pressure down a little, especially if you already have high or borderline-high blood pressure. So when you pair it with a pressure-lowering medicine like cyclothiazide, the two can add together and push your numbers a bit lower than expected.

For most people this is a mild, gentle effect, not a dramatic drop. Still, keep an eye out for feeling dizzy, lightheaded, or faint, especially when you stand up quickly. Everyday soy foods like tofu or edamame are unlikely to cause trouble, but concentrated soy isoflavone supplements are worth running by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. He J, Gu D, Wu X, et al. Effect of soybean protein on blood pressure: A randomized, controlled trial. Ann Intern Med 2005;143:1-9. PubMed
  2. Sacks FM, Lichtenstein A, Van Horn L, et al. Soy protein, isoflavones, and cardiovascular health. An American Heart Association Science Advisory for Professionals from the Nutrition Committee. Circulation 2006;113:1034-44. PubMed
  3. Altorf-van der Kuil, W., Engberink, M. F., Brink, E. J., van Baak, M. A., Bakker, S. J., Navis, G., van, 't, V, and Geleijnse, J. M. Dietary protein and blood pressure: a systematic review. PLoS.One. 2010;5(8):e12102. PubMed
Moderate

DIURETIC DRUGS

2 of 2

Cyclothiazide also falls under DIURETIC DRUGS.

Theoretically, soy might have additive effects when used with diuretic drugs.
Animal research suggests that genistein, a soy isoflavone, increases diuresis within 6 hours of subcutaneous administration in rats. The effects seem to be similar to those of furosemide. This effect has not been reported in humans.
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

Cyclothiazide is a thiazide-type water pill that helps your body get rid of extra salt and fluid, which lowers blood pressure. The thinking here is that soy might gently add to that fluid-losing effect. In simple terms, soy could in theory nudge things in the same direction your medication is already working.

Here's the honest part: this idea comes only from a rat study where a soy compound (genistein) acted a bit like a diuretic. It has not been seen in people, so I wouldn't lose sleep over it. Normal soy foods in your diet are very unlikely to cause trouble. If you take concentrated soy isoflavone supplements, just watch for extra dizziness, lightheadedness, or more frequent urination, and check with your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Gimenez, I., Martinez, R. M., Lou, M., Mayoral, J. A., Garay, R. P., and Alda, J. O. Salidiuretic action by genistein in the isolated, perfused rat kidney. Hypertension 1998;31(2):706-711. 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

Soy Also Interacts With Other Medications

Soy has 9 major, 342 moderate, 259 minor known drug interactions in our database — the Cyclothiazide one above is among them. If you take anything else, check it against the full list below.

Major 9 Moderate 342 Minor 259 No known interaction 2,220 (incl. Cyclothiazide)
Taking anything else?

Check Another of Your Medications Against Soy

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

Everything else you take

See Every Supplement That Interacts With Cyclothiazide

This page covers Soy only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cyclothiazide page lists 210 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: 10 major · 175 moderate · 25 minor.

From our pharmacist’s overview on the Cyclothiazide page

“Cyclothiazide (Fluidil, Anhydron) is a thiazide diuretic for high blood pressure and fluid retention, and its 210 supplement interactions warrant real vigilance, especially the ten rated major. Most entries pull in one of two directions.”

Reviewed by 2 · Jul 18, 2026

Open the Cyclothiazide interaction page

One more smart check

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

We hold 821 real supplement products containing Soy, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Soy. Your product may carry other ingredients that interact with Cyclothiazide too, on top of Soy — 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 Soy and Cyclothiazide 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 Soy
Top 25%

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

29 days ago today
Medication Cyclothiazide
Top half

#1,099 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 Soy

What is Soy?

  • Menopause symptoms (hot flashes)
  • Heart and cholesterol health
  • Bone health
  • Plant-based protein source
  • General nutrition

Soy is a nutritious bean that is a staple food and a popular source of plant protein and isoflavones. Eating soy foods as part of a balanced diet is generally considered safe for most people, and there is moderate evidence it may modestly help cholesterol and some menopause symptoms, though results vary. Talk with your pharmacist or doctor before using concentrated soy isoflavone supplements, especially if you have a history of hormone-sensitive conditions.

Read the full Soy monograph & all interactions
Keep checking

Other Drugs & Soy

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

9Major
342Moderate
259Minor
2,219No known interaction
9 Major 342 Moderate 259 Minor 2,219 No interaction
Major

9 interactions

Moderate

342 interactions

Showing 60 of 342 moderate interactions — see all 342 on the Soy page.

Minor

259 interactions

Showing 60 of 259 minor interactions — see all 259 on the Soy page.

No interaction 2,219 drugs checked — show the list

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

Showing the 60 most looked-up of 2,219 medications checked with no known interaction — see the full Soy list.

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

Can you take Soy with Cyclothiazide?
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 Soy and Cyclothiazide?
Cyclothiazide belongs to more than one drug category, and Soy 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 Soy and Cyclothiazide 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 Cyclothiazide and Soy?

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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.