Drug & supplement interaction

Vitamin D + Fosinopril, Hydrochlorothiazide

Fosinopril, Hydrochlorothiazide brand name: Monopril HCT.

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

Vitamin D has a moderate interaction with Fosinopril, Hydrochlorothiazide. Theoretically, taking thiazide diuretics and high-dose vitamin D can increase the risk of hypercalcemia.

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

Vitamin D and Fosinopril, Hydrochlorothiazide

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

Moderate

THIAZIDE DIURETICS

Why this applies to Fosinopril, Hydrochlorothiazide

Fosinopril, Hydrochlorothiazide falls under THIAZIDE DIURETICS — the group Vitamin D interacts with.

Theoretically, taking thiazide diuretics and high-dose vitamin D can increase the risk of hypercalcemia.
Thiazide diuretics decrease urinary calcium excretion, which could lead to hypercalcemia if vitamin D supplements are taken concurrently. This has been reported in people being treated with vitamin D for hypoparathyroidism, and also in elderly people with normal parathyroid function who were taking a thiazide, vitamin D, and calcium-containing antacids daily.
Severity Moderate 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

Your Monopril HCT contains hydrochlorothiazide, a thiazide water pill. One quirk of thiazides is that they tell your kidneys to hold onto a little more calcium instead of flushing it out. On its own that is usually no big deal, but if you pair it with high doses of vitamin D (which helps your body pull in more calcium), the two together can nudge your blood calcium up too far. This is called hypercalcemia.

If calcium climbs too high, you might feel things like nausea, constipation, unusual thirst, frequent urination, or feeling tired and foggy. To be fair, this is mostly reported with large vitamin D doses, sometimes alongside calcium antacids, and the evidence is fairly anecdotal. A typical daily vitamin D supplement is much less likely to cause trouble. Still, it is worth mentioning to your pharmacist or doctor, especially if you take extra calcium too.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Tatro DS, ed. Drug Interactions Facts. Facts and Comparisons Inc., St. Louis, MO. 1999.
  2. Crowe M, Wollner L, Griffiths RA. Hypercalcemia following vitamin D and thiazide therapy in the elderly. Practitioner 1984;228:312-3.
  3. Parfitt AM. Thiazide-induced hypercalcemia in vitamin D-treated hypoparathyroidism. Ann Intern Med 1972;77:557-63. PubMed
  4. Thiazide diuretics and the risk of osteoporosis. Pharmacist's Letter/Prescriber's Letter 2003;19(11):191105.
  5. Escribano, J., Balaguer, A., Pagone, F., Feliu, A., and Roque, I. Figuls. Pharmacological interventions for preventing complications in idiopathic hypercalciuria. Cochrane.Database.Syst.Rev. 2009;(1):CD004754. 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

Vitamin D Also Interacts With Other Medications

Vitamin D has 79 moderate, 637 minor known drug interactions in our database — the Fosinopril, Hydrochlorothiazide one above is one of them. If you take anything else, check it against the full list below.

Moderate 79 Minor 637 No known interaction 2,114 (incl. Fosinopril, Hydrochlorothiazide)
Taking anything else?

Check Another of Your Medications Against Vitamin D

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

From our Q&A

Questions About Vitamin D 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 Vitamin D 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 Vitamin D 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 Vitamin D as Part of a Dietary Supplement Product? Check It for Interactions

We hold 26,930 real supplement products containing Vitamin D, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Vitamin D. Your product may carry other ingredients that interact with Fosinopril, Hydrochlorothiazide too, on top of Vitamin D — 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 Vitamin D 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 Vitamin D
Top 10

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

29 days ago today
Medication Fosinopril, Hydrochlorothiazide
Top 5%

#97 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 Vitamin D

What is Vitamin D?

Vitamin D
  • Bone health and osteoporosis
  • Correcting vitamin D deficiency
  • Immune system support
  • Muscle strength in older adults
  • General supplementation when sun exposure is low

Vitamin D is a fat-soluble vitamin that helps your body absorb calcium and is important for healthy bones, muscles, and immune function. Many people, especially those with low sun exposure, benefit from supplementation, but more is not always better and very high doses can be harmful. Ask your pharmacist or doctor whether a blood test and supplement make sense for you.

Read the full Vitamin D monograph & all interactions
Keep checking

Other Drugs & Vitamin D

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

0Major
79Moderate
637Minor
2,113No known interaction
79 Moderate 637 Minor 2,113 No interaction
Moderate

79 interactions

Showing 60 of 79 moderate interactions — see all 79 on the Vitamin D page.

Minor

637 interactions

Showing 60 of 637 minor interactions — see all 637 on the Vitamin D page.

No interaction 2,113 drugs checked — show the list

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

Showing the 60 most looked-up of 2,113 medications checked with no known interaction — see the full Vitamin D list.

See the full Vitamin D 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
Vitamin D 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 Vitamin D and Fosinopril, Hydrochlorothiazide Together: Common Questions

Can you take Vitamin D with Fosinopril, 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 Vitamin D and Fosinopril, 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 Fosinopril, Hydrochlorothiazide and Vitamin D?

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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.