Drug & supplement interaction

Docosahexaenoic Acid (dha) + Hydrochlorothiazide

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

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

Docosahexaenoic Acid (dha) has a moderate interaction with Hydrochlorothiazide. Theoretically, taking DHA with antihypertensive drugs might increase the risk of hypotension.

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

Docosahexaenoic Acid (dha) 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 Docosahexaenoic Acid (dha) interacts with.

Theoretically, taking DHA with antihypertensive drugs might increase the risk of hypotension.
Fish oils containing DHA can lower blood pressure and might have additive effects in patients treated with antihypertensives; use with caution.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: DHA (a fish oil omega-3) can gently nudge your blood pressure down on its own. Since hydrochlorothiazide is already working to lower your blood pressure by clearing extra salt and water, putting the two together may add up to a slightly bigger drop than you'd get from the water pill alone. This isn't about DHA changing how your body breaks down the drug, it's just two blood-pressure-lowering effects stacking.

For most people this is mild, but watch for signs your pressure dipped too low: dizziness, lightheadedness when standing up, or feeling unusually tired. The evidence here is modest, and everyday fish-on-your-plate amounts are unlikely to matter much. Before adding a concentrated DHA supplement, just run it by your pharmacist or doctor so they can keep an eye on your numbers.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Prisco D, Paniccia R, Bandinelli B, et al. Effect of medium-term supplementation with a moderate dose of n-3 polyunsaturated fatty acids on blood pressure in mild hypertensive patients. Thromb Res 1998;1:105-12.
  2. Toft I, Bonaa KH, Ingebretsen OC, et al. Effects of n-3 polyunsaturated fatty acids on glucose homeostasis and blood pressure in essential hypertension. A randomized, controlled trial. Ann Intern Med 1995;123:911-8.
  3. Sacks FM, Hebert P, Appel LJ, et al. Short report: the effect of fish oil on blood pressure and high-density lipoprotein-cholesterol levels in phase I of the trials of hypertension prevention. J Hypertens 1994;12:209-13.
  4. Vandongen R, Mori TA, Burke V, et al. Effects on blood pressure of omega 3 fats in subjects at increased risk of cardiovascular disease. Hypertension 1993;22:371-9. PubMed
  5. Mori, T. A., Bao, D. Q., Burke, V., Puddey, I. B., and Beilin, L. J. Docosahexaenoic acid but not eicosapentaenoic acid lowers ambulatory blood pressure and heart rate in humans. Hypertension 1999;34(2):253-260. PubMed
  6. Nestel, P., Shige, H., Pomeroy, S., Cehun, M., Abbey, M., and Raederstorff, D. The n-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid increase systemic arterial compliance in humans. Am.J.Clin.Nutr. 2002;76(2):326-330. PubMed
  7. Woodman, R. J., Mori, T. A., Burke, V., Puddey, I. B., Barden, A., Watts, G. F., and Beilin, L. J. Effects of purified eicosapentaenoic acid and docosahexaenoic acid on platelet, fibrinolytic and vascular function in hypertensive type 2 diabetic patients PubMed
  8. Theobald, H. E., Goodall, A. H., Sattar, N., Talbot, D. C., Chowienczyk, P. J., and Sanders, T. A. Low-dose docosahexaenoic acid lowers diastolic blood pressure in middle-aged men and women. J Nutr 2007;137(4):973-978.

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

Docosahexaenoic Acid (dha) Also Interacts With Other Medications

Docosahexaenoic Acid (dha) has 374 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 374 No known interaction 2,456 (incl. Hydrochlorothiazide)
Taking anything else?

Check Another of Your Medications Against Docosahexaenoic Acid (dha)

Covers the 2,830 medications we’ve checked against Docosahexaenoic Acid (dha). Pick one to open its full report.

From our Q&A

Questions About Docosahexaenoic Acid (dha) 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 Docosahexaenoic Acid (dha) 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 Docosahexaenoic Acid (dha) 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

How much people look this up

Where Docosahexaenoic Acid (dha) 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 Docosahexaenoic Acid (dha)
Steady interest

#1,127 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Hydrochlorothiazide
Top 10%

#149 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 Docosahexaenoic Acid (dha)

What is Docosahexaenoic Acid (dha)?

Docosahexaenoic Acid (dha)
  • Brain and cognitive health
  • Eye and vision health
  • Fetal and infant development
  • Heart and triglyceride support
  • General omega-3 supplementation

DHA is an omega-3 fatty acid found in fatty fish and algae that is a building block for the brain, nervous system, and eyes. It is widely used and generally well tolerated, with the strongest support for fetal/infant development and lowering triglycerides; evidence for many other uses is mixed. Talk with your pharmacist or doctor before starting, especially if you are pregnant, have a bleeding risk, or take blood thinners.

Read the full Docosahexaenoic Acid (dha) 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. The capsule form is indicated specifically for hypertension management.

It also treats edema (fluid buildup) associated with congestive heart failure, liver cirrhosis, and kidney diseases including nephrotic syndrome. The tablet form is additionally indicated for edema caused by corticosteroid and estrogen therapy, as well as conditions such as acute glomerulonephritis and chronic renal failure. Inzirqo (the oral suspension) is indicated for both hypertension and edema in adult and pediatric patients.

See full Hydrochlorothiazide drug information
Keep checking

Other Drugs & Docosahexaenoic Acid (dha)

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

0Major
374Moderate
0Minor
2,455No known interaction
374 Moderate 2,455 No interaction
Moderate

374 interactions

Showing 60 of 374 moderate interactions — see all 374 on the Docosahexaenoic Acid (dha) page.

No interaction 2,455 drugs checked — show the list

We also checked Docosahexaenoic Acid (dha) against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,455 medications checked with no known interaction — see the full Docosahexaenoic Acid (dha) list.

See the full Docosahexaenoic Acid (dha) 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
Docosahexaenoic Acid (dha) 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 Docosahexaenoic Acid (dha) and Hydrochlorothiazide Together: Common Questions

Can you take Docosahexaenoic Acid (dha) 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 Docosahexaenoic Acid (dha) 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 Docosahexaenoic Acid (dha)?

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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.