Drug & supplement interaction

Flaxseed Oil + Hydrochlorothiazide

Hydrochlorothiazide brand names: Esidrix, Hydro, Microzide, HydroDiuril, Hydro-D, and others.

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

Flaxseed Oil has a moderate interaction with Hydrochlorothiazide. Theoretically, combining flaxseed oil with other antihypertensive drugs might have additive effects and increase the risk of hypotension.

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

Flaxseed Oil and Hydrochlorothiazide

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

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Hydrochlorothiazide

Hydrochlorothiazide falls under ANTIHYPERTENSIVE DRUGS — the group Flaxseed Oil interacts with.

Theoretically, combining flaxseed oil with other antihypertensive drugs might have additive effects and increase the risk of hypotension.
Some clinical evidence suggests that long-term consumption of flaxseed oil can modestly lower systolic and diastolic blood pressure, while other clinical research shows no effect.
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 simple version: hydrochlorothiazide (Microzide) already works to lower your blood pressure. Flaxseed oil might nudge your blood pressure down a little bit on its own too. Put them together and, in theory, those two small effects could add up and leave your pressure lower than expected.

I want to be honest about how soft this concern is. It's based on pharmacology and mixed research, not strong proof, and some studies show flaxseed oil does nothing to blood pressure at all. Most people combine the two without trouble. Just keep an eye out for signs of low blood pressure, like dizziness, lightheadedness when you stand up, or feeling unusually tired. If you notice those, or before you start flaxseed oil, check in with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Paschos GK, Magkos F, Panagiotakos DB, et al. Dietary supplementation with flaxseed oil lowers blood pressure in dyslipidaemic patients. Eur J Clin Nutr 2007;61:1201-6. PubMed
  2. Ursoniu S, Sahebkar A, Andrica F, Serban C, Banach M; Lipid and Blood Pressure Meta-analysis Collaboration Group. Effects of flaxseed supplements on blood pressure: a systematic review and meta-analysis of controlled clinical trial. Clin Nutr. 2016 Jun;3 PubMed
  3. Morshedzadeh N, Shahrokh S, Aghdaei HA, et al. Effects of flaxseed and flaxseed oil supplement on serum levels of inflammatory markers, metabolic parameters and severity of disease in patients with ulcerative colitis. Complement Ther Med. 2019;46:36-43. PubMed
  4. Saleh-Ghadimi S, Kheirouri S, Golmohammadi A, Moludi J, Jafari-Vayghan H, Alizadeh M. Effect of flaxseed oil supplementation on anthropometric and metabolic indices in patients with coronary artery disease: A double-blinded randomized controlled trial. J PubMed
  5. Li L, Li H, Gao Y, Vafaei S, Zhang X, Yang M. Effect of flaxseed supplementation on blood pressure: a systematic review, and dose-response meta-analysis of randomized clinical trials. Food Funct 2023;14(2):675-690. PubMed
  6. Mahmudiono T, Jasim SA, Karim YS, et al. The effect of flaxseed oil consumption on blood pressure among patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized clinical trials. Phytother Res 2022;36(10):

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

Flaxseed Oil Also Interacts With Other Medications

Flaxseed Oil has 292 moderate known drug interactions in our database — the Hydrochlorothiazide one above is one of them. If you take anything else, check it against the full list below.

Moderate 292 No known interaction 2,538 (incl. Hydrochlorothiazide)
Taking anything else?

Check Another of Your Medications Against Flaxseed Oil

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

From our Q&A

Questions About Flaxseed Oil or Hydrochlorothiazide

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

This page covers Flaxseed Oil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Hydrochlorothiazide page lists 230 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 · 195 moderate · 25 minor.

From our pharmacist’s overview on the Hydrochlorothiazide page

“Hydrochlorothiazide sits at the strong end of the caution scale for supplement interactions, and the small group of major-rated entries deserves a careful read before everything else on the page. Most of what appears here either adds to the pill's blood-pressure-lowering effect or piles onto its diuretic action, pushing fluid and potas…”

Reviewed by 2 · Jul 18, 2026

Open the Hydrochlorothiazide interaction page

One more smart check

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

We hold 1,329 real supplement products containing Flaxseed Oil, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Flaxseed Oil. Your product may carry other ingredients that interact with Hydrochlorothiazide too, on top of Flaxseed Oil — 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 Flaxseed Oil and Hydrochlorothiazide 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 Flaxseed Oil
Top 25%

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

29 days ago today
Medication Hydrochlorothiazide
Top 10%

#143 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 Flaxseed Oil

What is Flaxseed Oil?

  • Source of omega-3 (ALA) fatty acids
  • Heart and cholesterol health
  • Dry skin and inflammation
  • Constipation
  • General wellness

Flaxseed oil is a plant-based source of the omega-3 fatty acid ALA, which the body can partly convert to the omega-3s found in fish oil. It may help support heart health and provide healthy fats, but evidence for most specific health claims is limited or mixed. It is generally well tolerated, but talk to your pharmacist or doctor before starting, especially if you are pregnant or have a bleeding risk.

Read the full Flaxseed Oil monograph & all interactions
Medication

About Hydrochlorothiazide

What Is Hydrochlorothiazide Used For?

Brand names: Esidrix, Hydro, Microzide, HydroDiuril, Hydro-D, Oretic, Aquazide H, Aquazide, HCTZ

Hydrochlorothiazide treats high blood pressure (hypertension) in adults and children, either alone or combined with other blood pressure medicines. Lowering blood pressure reduces the risk of strokes and heart attacks.

It also treats edema (fluid buildup) linked to congestive heart failure, hepatic cirrhosis (liver scarring), and kidney conditions including nephrotic syndrome. Hydrochlorothiazide tablets are additionally indicated for edema caused by corticosteroid or estrogen therapy, and edema from acute glomerulonephritis or chronic renal failure. Inzirqo (the oral suspension) is specifically approved for both hypertension and edema in adult and pediatric patients.

See full Hydrochlorothiazide drug information
Keep checking

Other Drugs & Flaxseed Oil

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

0Major
292Moderate
0Minor
2,537No known interaction
292 Moderate 2,537 No interaction
Moderate

292 interactions

Showing 60 of 292 moderate interactions — see all 292 on the Flaxseed Oil page.

No interaction 2,537 drugs checked — show the list

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

Showing the 60 most looked-up of 2,537 medications checked with no known interaction — see the full Flaxseed Oil list.

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

Can you take Flaxseed Oil with Hydrochlorothiazide?
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 Flaxseed Oil and Hydrochlorothiazide 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 and Flaxseed Oil?

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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.