Drug & supplement interaction

Vitamin D + Diltiazem, Enalapril

Diltiazem, Enalapril brand name: Teczem.

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

Diltiazem, Enalapril falls into 2 drug categories that Vitamin D can interact with; the most serious is rated moderate. Theoretically, hypercalcemia induced by high-dose vitamin D can reduce the therapeutic effects of diltiazem for arrhythmia.

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

Vitamin D and Diltiazem, Enalapril

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

Why Are There 2 Interactions?

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

Moderate

DILTIAZEM (Cardizem, others)

1 of 2
Theoretically, hypercalcemia induced by high-dose vitamin D can reduce the therapeutic effects of diltiazem for arrhythmia.
High doses of vitamin D can cause hypercalcemia. Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation. Theoretically this could also occur with diltiazem. Avoid vitamin D doses above the tolerable upper intake level (4000 IU daily for adults) and monitor serum calcium levels in people taking vitamin D and diltiazem concurrently.
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 gist for your Teczem, which combines diltiazem (a calcium channel blocker) with enalapril (a blood pressure medicine). The concern isn't with normal vitamin D doses. It's only if you take very high amounts over time, which can push your blood calcium too high. Since diltiazem works partly by affecting calcium movement in heart cells, extra calcium in the blood could blunt how well it controls a fast or irregular heartbeat.

This is mostly theoretical and seen more with verapamil, a close cousin of diltiazem. A typical daily vitamin D supplement is very unlikely to cause trouble. Just stay at or below 4000 IU a day unless your doctor advised more, and check with your pharmacist if you're on high-dose D so they can keep an eye on your calcium.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Bar-Or D, Yoel G. Calcium and calciferol antagonize effect of verapamil in atrial fibrillation. Br Med J 1981;282:1585-6.
Minor

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Why this applies to Diltiazem, Enalapril

Diltiazem, Enalapril falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Vitamin D interacts with.

Vitamin D might induce CYP3A4 enzymes and reduce the bioavailability of CYP3A4 substrates.
There is some concern that vitamin D might induce CYP3A4. In vitro research suggests that vitamin D induces CYP3A4 transcription. Additionally, observational research has found that increased UV light exposure and serum vitamin D levels are associated with decreased serum levels of CYP3A4 substrates such as tacrolimus and sirolimus, while no association between UV light exposure or vitamin D levels and levels of mycophenolic acid, a non-CYP3A4 substrate, was found. A small, low-quality clinical study shows that taking vitamin D reduces levels of the CYP3A4 substrate atorvastatin and its active metabolites by up to 55%; however, the clinical effects of atorvastatin were not reduced. While researchers theorized that vitamin D might induce CYP3A4, this proposed mechanism was not specifically studied.
Severity Minor 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

This combination pill pairs diltiazem (a blood pressure and heart-rate medicine) with enalapril (an ACE inhibitor). The diltiazem half is processed by a liver enzyme called CYP3A4, and there is a theory that vitamin D may slightly speed that enzyme up. If that happened, your body could clear diltiazem a bit faster, which in theory might make it work less well. That could mean blood pressure or heart rate creeping back up.

Honestly though, this is a minor, theory-only concern based mostly on lab studies, and normal vitamin D doses are very unlikely to change how your medicine works. Enalapril isn't really affected here. Keep taking your vitamin D as directed, and just check in with your pharmacist or doctor if you have questions.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Schwartz JB. Effects of vitamin D supplementation in atorvastatin-treated patients: A new drug interaction with an unexpected consequence. Clin Pharmacol Ther 2009;85:198-203. PubMed
  2. Wang Z, Schuetz EG, Xu Y, Thummel KE. Interplay between vitamin D and the drug metabolizing enzyme CYP3A4. J Steroid Biochem Mol Biol 2013;136:54-8. 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, 635 minor known drug interactions in our database — the Diltiazem, Enalapril one above is among them. If you take anything else, check it against the full list below.

Moderate 79 Minor 635 No known interaction 2,116 (incl. Diltiazem, Enalapril)
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 Diltiazem, Enalapril

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 Diltiazem, Enalapril, 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 Diltiazem, Enalapril

This page covers Vitamin D only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Diltiazem, Enalapril page lists 271 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 Coleus (major).

By severity: 9 major · 220 moderate · 42 minor.

From our pharmacist’s overview on the Diltiazem, Enalapril page

“Anyone taking Teczem (diltiazem with enalapril) for blood pressure should know that most of the 271 supplements with an interaction on file hit the same targets as the drug itself. The bulk either add to its blood-pressure-lowering effect or change how the body handles diltiazem, which is processed by an enzyme called CYP3A4.”

Reviewed by 2 · Jul 18, 2026

Open the Diltiazem, Enalapril 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 Diltiazem, Enalapril 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 Diltiazem, Enalapril 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

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

29 days ago today
Medication Diltiazem, Enalapril
Top 5%

#142 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
635Minor
2,115No known interaction
79 Moderate 635 Minor 2,115 No interaction
Moderate

79 interactions

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

Minor

635 interactions

Showing 60 of 635 minor interactions — see all 635 on the Vitamin D page.

No interaction 2,115 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 2,115 medications checked with no known interaction — see the full Vitamin D list.

See the full Vitamin D interactions page
See every supplement checked against Diltiazem, Enalapril, 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 Diltiazem, Enalapril supplement interactions › Every supplement checked against Diltiazem, Enalapril, 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 Diltiazem, Enalapril Together: Common Questions

Can you take Vitamin D with Diltiazem, Enalapril?
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.
Why are there 2 interactions listed for Vitamin D and Diltiazem, Enalapril?
Diltiazem, Enalapril belongs to more than one drug category, and Vitamin D 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 Vitamin D and Diltiazem, Enalapril 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

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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.