Drug & supplement interaction

Fish Oil + Spironolactone

Spironolactone brand names: Aldactone, Spiroton, Carospir.

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

Fish Oil has a moderate interaction with Spironolactone. Theoretically, taking fish oil 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

Fish Oil and Spironolactone

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

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Spironolactone

Spironolactone falls under ANTIHYPERTENSIVE DRUGS — the group Fish Oil interacts with.

Theoretically, taking fish oil with antihypertensive drugs might increase the risk of hypotension.
Clinical evidence indicates that fish oils can modestly lower blood pressure and might have additive effects in patients treated with antihypertensives.
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: fish oil can gently lower blood pressure on its own. Since spironolactone is also working to bring your blood pressure down (and to remove extra fluid), putting the two together can add up. The concern isn't that fish oil changes how spironolactone is broken down. It's just that two blood-pressure-lowering effects can stack.

For most folks this is mild, but watch for signs your pressure dipped too low, like feeling dizzy, lightheaded, or unsteady when you stand up. The evidence here is on the weaker side, and fish oil's effect is usually modest. Still, it's worth a quick chat with your pharmacist or doctor, especially if you already notice low readings or take other blood pressure meds.

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. Bonaa, K. H., Bjerve, K. S., Straume, B., Gram, I. T., and Thelle, D. Effect of eicosapentaenoic and docosahexaenoic acids on blood pressure in hypertension. A population-based intervention trial from the Tromso study. N Engl J Med 3-22-1990;322(12):795- DOI
  6. Singer, P., Melzer, S., Goschel, M., and Augustin, S. Fish oil amplifies the effect of propranolol in mild essential hypertension. Hypertension 1990;16(6):682-691. PubMed
  7. Knapp, H. R. and FitzGerald, G. A. The antihypertensive effects of fish oil. A controlled study of polyunsaturated fatty acid supplements in essential hypertension. N Engl J Med 4-20-1989;320(16):1037-1043. PubMed
  8. Lungershausen, Y. K., Abbey, M., Nestel, P. J., and Howe, P. R. Reduction of blood pressure and plasma triglycerides by omega-3 fatty acids in treated hypertensives. J Hypertens. 1994;12(9):1041-1045. DOI
  9. Appel, L. J., Miller, E. R., III, Seidler, A. J., and Whelton, P. K. Does supplementation of diet with 'fish oil' reduce blood pressure? A meta-analysis of controlled clinical trials. Arch Intern Med 6-28-1993;153(12):1429-1438. DOI
  10. Morris, M. C., Sacks, F., and Rosner, B. Does fish oil lower blood pressure? A meta-analysis of controlled trials. Circulation 1993;88(2):523-533. PubMed
  11. Morris, M. C., Taylor, J. O., Stampfer, M. J., Rosner, B., and Sacks, F. M. The effect of fish oil on blood pressure in mild hypertensive subjects: a randomized crossover trial. Am J Clin Nutr 1993;57(1):59-64. 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

Fish Oil Also Interacts With Other Medications

Fish Oil has 206 moderate, 120 minor known drug interactions in our database — the Spironolactone one above is one of them. If you take anything else, check it against the full list below.

Moderate 206 Minor 120 No known interaction 2,504 (incl. Spironolactone)
Taking anything else?

Check Another of Your Medications Against Fish Oil

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

From our Q&A

Questions About Fish Oil or Spironolactone

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

This page covers Fish Oil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Spironolactone page lists 206 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), Lithium (major) and Oleander (major).

By severity: 7 major · 174 moderate · 25 minor.

From our pharmacist’s overview on the Spironolactone page

“Potassium is the supplement I check first for anyone on spironolactone (Aldactone, Carospir), because this water pill works by holding potassium in the body, and supplementing more on top of that can push blood levels too high. It is one of 206 supplement and herbal ingredients with documented interactions here, and the list warrants g…”

Reviewed by 2 · Jul 18, 2026

Open the Spironolactone interaction page

One more smart check

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

We hold 4,777 real supplement products containing Fish Oil, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fish Oil. Your product may carry other ingredients that interact with Spironolactone too, on top of Fish 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 Fish Oil and Spironolactone 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 Fish Oil
Top 5%

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

29 days ago today
Medication Spironolactone
Top 10%

#156 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 Fish Oil

What is Fish Oil?

Fish Oil
  • High triglycerides
  • Heart health
  • Joint pain and inflammation
  • Brain and eye health
  • Dry eyes

Fish oil provides omega-3 fatty acids (EPA and DHA) that are best known for lowering high triglyceride levels. The evidence for other heart and health benefits is mixed, and it is generally well tolerated. Talk with your pharmacist or doctor before starting it, especially if you take blood thinners or have a fish allergy.

Read the full Fish Oil monograph & all interactions
Medication

About Spironolactone

What Is Spironolactone Used For?

Brand names: Aldactone, Spiroton, Carospir

Spironolactone tablets and spironolactone oral suspension are used to treat several conditions. Both forms treat NYHA Class III–IV heart failure with reduced ejection fraction — helping patients survive longer, reducing fluid buildup, and lowering the need for hospitalization. Both are also used as add-on therapy for high blood pressure when other medicines aren't enough, and to manage fluid buildup (edema) in adults with liver cirrhosis.

Spironolactone tablets (including Aldactone) are additionally approved to manage edema in nephrotic syndrome (a kidney disorder causing protein loss and swelling) and to treat primary hyperaldosteronism — a condition where the adrenal glands overproduce the hormone aldosterone — both before surgery and as long-term therapy for patients who can't or won't have surgery. The oral suspension is not approved for nephrotic syndrome or primary hyperaldosteronism.

See full Spironolactone drug information
Keep checking

Other Drugs & Fish Oil

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

0Major
206Moderate
120Minor
2,503No known interaction
206 Moderate 120 Minor 2,503 No interaction
Moderate

206 interactions

Showing 60 of 206 moderate interactions — see all 206 on the Fish Oil page.

Minor

120 interactions

Showing 60 of 120 minor interactions — see all 120 on the Fish Oil page.

No interaction 2,503 drugs checked — show the list

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

Showing the 60 most looked-up of 2,503 medications checked with no known interaction — see the full Fish Oil list.

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

Can you take Fish Oil with Spironolactone?
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 Fish Oil and Spironolactone 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 Spironolactone and Fish 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.