Drug & supplement interaction

Lithium + Fosinopril, Hydrochlorothiazide

Fosinopril, Hydrochlorothiazide brand name: Monopril HCT.

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

Fosinopril, Hydrochlorothiazide falls into 2 drug categories that Lithium can interact with; the most serious is rated major. Theoretically, taking lithium supplements with loop diuretics might increase lithium levels and adverse effects.

Read the full interaction report
SeverityMajor
LikelihoodProbable
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Lithium and Fosinopril, Hydrochlorothiazide

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

Why Are There 2 Interactions?

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

Major

DIURETIC DRUGS

1 of 2

Why this applies to Fosinopril, Hydrochlorothiazide

Fosinopril, Hydrochlorothiazide falls under DIURETIC DRUGS — the group Lithium interacts with.

Theoretically, taking lithium supplements with loop diuretics might increase lithium levels and adverse effects.
Thiazide diuretics and loop diuretics might reduce lithium excretion, particularly in sodium-restricted patients. If lithium is clinically indicated and other treatment options are unavailable or inadequate in patients using diuretics, lithium treatment can be initiated with extreme caution. Serum lithium should be measured frequently and the doses used should be the lowest dose ordinarily tolerated. It is unclear if this interaction would be clinically significant with the smaller doses found in lithium supplements.
Severity Major Likelihood Probable Evidence D

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 key thing about your blood pressure pill: it contains hydrochlorothiazide, a thiazide water pill. Thiazides make your kidneys hold onto lithium instead of clearing it out, so lithium can quietly build up in your blood. That matters because lithium has a very narrow safe range, and even a small rise can tip you into trouble. Warning signs of too much lithium include nausea, diarrhea, hand tremors, feeling unusually drowsy or confused, slurred speech, or unsteady walking.

This concern is based on how these drugs behave rather than on hard studies, and it's unclear whether the tiny amounts in lithium supplements (like lithium orotate) are enough to cause it. Still, please don't combine them on your own. Loop in your pharmacist or doctor first so they can check whether it's safe for you.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Martindale W. Martindale the Extra Pharmacopoeia. Pharmaceutical Press, 1999.
  2. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  3. https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/017812s028,018421s027lbl.pdf. Accessed Nov. 21, 2018
Moderate

ACE INHIBITORS (ACEIs)

2 of 2

Fosinopril, Hydrochlorothiazide also falls under ACE INHIBITORS (ACEIs).

Theoretically, taking lithium supplements with ACEIs might increase levels and adverse effects of lithium.
Concomitant administration of ACEIs with lithium may increase lithium concentrations. It is unclear if this interaction would be clinically significant with the smaller doses found in lithium supplements.
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 something worth knowing about Monopril HCT, which combines fosinopril (an ACE inhibitor) with hydrochlorothiazide (a water pill). Both of these can affect how your kidneys handle lithium. ACE inhibitors and diuretics tend to make your body hold onto lithium, so the lithium in your blood can creep upward. If lithium levels climb too high, you may notice things like nausea, tremor or shakiness, unusual thirst, confusion, or feeling unsteady.

Now, the honest part: this concern is mostly theoretical, based on how these medicines work rather than strong studies, especially with the tiny amounts in over-the-counter lithium supplements like lithium orotate. Still, lithium has a narrow safety window, so please don't combine them without checking. Talk with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Martindale W. Martindale the Extra Pharmacopoeia. Pharmaceutical Press, 1999.
  2. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.

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

Lithium Also Interacts With Other Medications

Lithium has 258 major, 256 moderate known drug interactions in our database — the Fosinopril, Hydrochlorothiazide one above is among them. If you take anything else, check it against the full list below.

Major 258 Moderate 256 No known interaction 2,316 (incl. Fosinopril, Hydrochlorothiazide)
Taking anything else?

Check Another of Your Medications Against Lithium

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

From our Q&A

Questions About Lithium or Fosinopril, 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 Lithium or Fosinopril, 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 Fosinopril, Hydrochlorothiazide

This page covers Lithium only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fosinopril, Hydrochlorothiazide page lists 238 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: 11 major · 200 moderate · 27 minor.

From our pharmacist’s overview on the Fosinopril, Hydrochlorothiazide page

“Monopril HCT combines two blood pressure medicines, the ACE inhibitor fosinopril and the water pill hydrochlorothiazide, which is why I read its supplement list with genuine wariness rather than a shrug. Eleven of the 238 ingredients on file carry a major rating and deserve your attention first, while most of the 200 rated moderate eit…”

Reviewed by 2 · Jul 18, 2026

Open the Fosinopril, Hydrochlorothiazide interaction page

One more smart check

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

We hold 330 real supplement products containing Lithium, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Lithium. Your product may carry other ingredients that interact with Fosinopril, Hydrochlorothiazide too, on top of Lithium — 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 Lithium and Fosinopril, 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 Lithium
Top 25%

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

29 days ago today
Medication Fosinopril, Hydrochlorothiazide
Steady interest

#1,510 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 Lithium

What is Lithium?

Lithium
  • Mood support
  • Bipolar disorder (prescription)
  • Healthy mental function
  • Irritability or stress
  • Sleep support

Lithium is a naturally occurring metal that, in prescription form (lithium carbonate or citrate), is an FDA-approved, well-proven treatment for bipolar disorder. Low-dose supplement forms like lithium orotate are sold for mood support, but there is very little reliable evidence that they work, and even small amounts of lithium can be risky for some people. Always talk to a pharmacist or doctor before taking any lithium product.

Read the full Lithium monograph & all interactions
Keep checking

Other Drugs & Lithium

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

258Major
256Moderate
0Minor
2,315No known interaction
258 Major 256 Moderate 2,315 No interaction
Major

258 interactions

Showing 60 of 258 major interactions — see all 258 on the Lithium page.

Moderate

256 interactions

Showing 60 of 256 moderate interactions — see all 256 on the Lithium page.

No interaction 2,315 drugs checked — show the list

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

Showing the 60 most looked-up of 2,315 medications checked with no known interaction — see the full Lithium list.

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

Can you take Lithium with Fosinopril, Hydrochlorothiazide?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Lithium and Fosinopril, Hydrochlorothiazide?
Fosinopril, Hydrochlorothiazide belongs to more than one drug category, and Lithium 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 Lithium and Fosinopril, Hydrochlorothiazide interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Fosinopril, Hydrochlorothiazide and Lithium?

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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.