Drug & supplement interaction

Borage + Diltiazem

Diltiazem brand names: Cardizem, Cardizem SR, Diltiaz SR, Cardizem CD, Tiazac, and others.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Borage and Diltiazem in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Borage and Diltiazem

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Diltiazem and Borage in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Borage safety at a glance

Borage overall Use caution Seed oil that is certified pyrrolizidine alkaloid (PA)-free is generally better tolerated, but other parts may harm the liver.
Pregnancy Likely Unsafe When products containing hepatotoxic pyrrolizidine alkaloids (PA) are used orally. Borage plant parts, such as the leaf, flower, and seed, can contain hepatotox... Read the full pregnancy detail
Breastfeeding Likely Unsafe When products containing hepatotoxic pyrrolizidine alkaloids (PA) are used orally. Borage plant parts, such as the leaf, flower, and seed, can contain hepatotox... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Diltiazem and Borage? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Diltiazem

Interactions in our licensed database are recorded against drug classes, not just single drug names. Diltiazem is filed under 9 classifications — including calcium channel blockers, cytochrome p450 1a2 (cyp1a2) inhibitors, cytochrome p450 3a4 (cyp3a4) inhibitors. Borage has documented interactions with 3 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate), cytochrome p450 3a4 (cyp3a4) inducers (moderate) and phenothiazines (moderate) — and none of Diltiazem’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Borage Does Interact With Other Medications

Borage has 226 moderate known drug interactions in our database — Diltiazem isn’t one of them. If you take anything else, check it against the full list below.

Moderate 226 No known interaction 2,604 (incl. Diltiazem)
Taking anything else?

Check Another of Your Medications Against Borage

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

What to actually watch for

No Interaction Found — But Data Suggests Borage and Diltiazem May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Bloating or gas / Diarrhea reported in 6.1% of FDA reports for Diltiazem Additional detail

    Borage

    “Orally, borage seed oil can cause soft stools, diarrhea, belching, and bloating.”

    Borage · Natural Medicines adverse-effect record, reported in diarrhea.

    2 sources cited
    1. 8013. Fan YY, Chapkin RS. Importance of dietary gamma-linolenic acid in human health and nutrition. J Nutr 1998;128:1411-4.
    2. 11341. Takwale A, Tan E, Agarwal S, et al. Efficacy and tolerability of borage oil in adults and children with atopic eczema: randomised, double blind, placebo controlled, parallel group trial. BMJ 2003;327:1385. PubMed

    Diltiazem

    Listed in the ADVERSE REACTIONS section of the FDA label for Diltiazem, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

  • Vomiting Additional detail

    Borage

    “The pyrrolizidine alkaloid (PA) constituents of borage can cause significant hepatotoxicity. PAs can occur in borage leaf, flower, and seed; borage seed oil contains little to no PAs. Chronic exposure to other plants containing hepatotoxic PA constituents has been associated with veno-occlusive disease (VOD). Subacute VOD causes vague symptoms with persistent liver enlargement.”

    Borage · Natural Medicines adverse-effect record, reported in diarrhea.

    3 sources cited
    1. 12841. Chojkier M. Hepatic sinusoidal-obstruction syndrome: toxicity of pyrrolizidine alkaloids. J Hepatol 2003;39:437-46. PubMed
    2. 12842. Roeder E. Medicinal plants in Europe containing pyrrolizidine alkaloids. Pharmazie 1995;50:83-98.
    3. 4021. WHO working group. Pyrrolizidine alkaloids. Environmental Health Criteria, 80. WHO: Geneva, 1988.

    Diltiazem

    Listed in the ADVERSE REACTIONS section of the FDA label for Diltiazem. Read the label on DailyMed ›

Reported for Borage but not commonly for Diltiazem: liver problems.

Effects for Diltiazem come from the ADVERSE REACTIONS section of its FDA label; effects for Borage come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 34,400 voluntary FDA FAERS reports for Diltiazem that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Borage in Pregnancy & Breastfeeding

Pregnancy And Lactation Likely Unsafe

When products containing hepatotoxic pyrrolizidine alkaloids (PA) are used orally. Borage plant parts, such as the leaf, flower, and seed, can contain hepatotoxic PAs. Repeated exposure to low concentrations of hepatotoxic PAs can cause severe veno-occlusive disease. Hepatotoxic PAs might also be carcinogenic, mutagenic, and teratogenic. These constituents are also excreted in breast milk. Tell patients to avoid borage preparations that are not certified and labeled as hepatotoxic PA-free. There is insufficient reliable information available about the safety of borage seed oil when used orally or topically during pregnancy or lactation.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

From our Q&A

Questions About Borage or Diltiazem

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

This page covers Borage only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Diltiazem page lists 260 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), Coleus (major) and Grapefruit (major).

By severity: 7 major · 214 moderate · 39 minor.

From our pharmacist’s overview on the Diltiazem page

“Someone on diltiazem (Cardizem, Tiazac) is usually managing blood pressure, angina, or a fast heart rhythm, so this list deserves genuine care. Seven of the 260 ingredients on file carry a major rating, and two of those are things people actually buy: grapefruit, which blocks the enzyme that clears diltiazem and can push its blood leve…”

Reviewed by 2 · Jul 18, 2026

Open the Diltiazem interaction page

One more smart check

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

We hold 122 real supplement products containing Borage, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Borage. Even though Borage itself has no known interaction with Diltiazem, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Borage and Diltiazem 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 Borage
Top 25%

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

29 days ago today
Medication Diltiazem
Top 10%

#214 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Borage reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Borage and Diltiazem records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Borage

What is Borage?

Borage
  • Eczema and dry skin
  • Rheumatoid arthritis
  • Inflammation
  • Respiratory complaints
  • Mood and stress

Borage is a Mediterranean herb whose seed oil is rich in gamma-linolenic acid (GLA), an omega-6 fatty acid studied mostly for skin conditions and arthritis with mixed results. The plant's leaves and flowers can contain liver-toxic pyrrolizidine alkaloids, so only use products clearly labeled 'PA-free' and talk to your pharmacist or doctor before taking it.

Borago officinalis · Boraginaceae · Seeds (for oil), leaves, and flowers · Borage seed oil capsules, topical oil, tea, dried leaf/flower

An interaction check asks whether these two react with each other — it does not ask whether Borage is a good idea for someone in your situation. Here is what our Borage record says about it on its own.

Borage: dosing

There is no official, standardized dose of borage. Borage seed oil products are usually sold as capsules standardized to a certain amount of GLA, and the right amount can vary by product and purpose.The safest approach is to follow the directions on the product label and to choose a brand that states it is free of pyrrolizidine alkaloids.

From our Borage monograph — the full record covers uses, side effects and every documented interaction.

Read the full Borage monograph & all interactions
Medication

About Diltiazem

What Is Diltiazem Used For?

Brand names: Cardizem, Cardizem SR, Diltiaz SR, Cardizem CD, Tiazac, Diltiaz XT, Diltiaz CD, Dilacor, Diltiaz, Cardizem LA, Dilacor XR, Cartia XT, Tiamate, Adizem-SR, Adizem-XL, Angitil SR, Angitil XL, Calcicard CR, Dilcardia SR, Dilzem SR, Dilzem XL, Slozem, Tildiem LA, Tildiem Retard, Viazem XL, Zemtard 120XL, Zemtard 180XL, Zemtard 240XL, Zemtard 300XL

Oral extended-release forms of diltiazem — including Matzim LA, Cardizem LA, Cartia, Cartia XT, Tiadylt ER, and various generic capsules and tablets — are used to treat high blood pressure (hypertension) and chronic stable angina (chest pain brought on by activity). Some capsule formulations, including Cartia, Cartia XT, and certain generics, are also approved for angina due to coronary artery spasm (sudden chest pain caused by a sudden tightening of a coronary artery).

Injectable forms of diltiazem are used in hospital settings to temporarily slow a dangerously fast heart rate in atrial fibrillation or atrial flutter (rapid, irregular heart rhythms), and to restore a normal heart rhythm in paroxysmal supraventricular tachycardia (PSVT) — sudden episodes of a very fast but regular heartbeat originating above the heart's lower chambers.

Most-Reported Side Effects for Diltiazem

From FAERS, the FDA’s public side-effect reporting system (34,400 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Dyspnea 3,309 reports
Fatigue 2,733 reports
Nausea 2,454 reports
Dizziness 2,174 reports
Diarrhea 2,113 reports
See full Diltiazem drug information
Keep checking

Other Drugs & Borage

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

0Major
226Moderate
0Minor
2,603No known interaction
226 Moderate 2,603 No interaction
Moderate

226 interactions

Showing 60 of 226 moderate interactions — see all 226 on the Borage page.

No interaction 2,603 drugs checked — show the list

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

Showing the 60 most looked-up of 2,603 medications checked with no known interaction — see the full Borage list.

See the full Borage interactions page
See every supplement checked against Diltiazem, ranked by severity
Evidence & sources

Borage References

The 11 references that drive our Borage monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Guivernau M, Meza N, Barja P, Roman O. Clinical and experimental study on the long-term effect of dietary gamma-linolenic acid on plasma lipids, platelet aggregation, thromboxane formation, and prostacyclin production. Prostaglandins Leukot Essent Fatty A PubMed
  2. WHO working group. Pyrrolizidine alkaloids. Environmental Health Criteria, 80. WHO: Geneva, 1988.
  3. Fan YY, Chapkin RS. Importance of dietary gamma-linolenic acid in human health and nutrition. J Nutr 1998;128:1411-4.
  4. Takwale A, Tan E, Agarwal S, et al. Efficacy and tolerability of borage oil in adults and children with atopic eczema: randomised, double blind, placebo controlled, parallel group trial. BMJ 2003;327:1385. PubMed
  5. Chojkier M. Hepatic sinusoidal-obstruction syndrome: toxicity of pyrrolizidine alkaloids. J Hepatol 2003;39:437-46. PubMed
  6. Roeder E. Medicinal plants in Europe containing pyrrolizidine alkaloids. Pharmazie 1995;50:83-98.
  7. Wang YP, Yan J, Fu PP, Chou MW. Human liver microsomal reduction of pyrrolizidine alkaloid N-oxides to form the corresponding carcinogenic parent alkaloid. Toxicol Lett 2005;155:411-20. PubMed
  8. Holman CP and Bell AF. A trial of evening primrose oil in the treatment of chronic schizophrenia. J Orhtomolecular Psych 1983;12:302-304.
  9. Vaddadi KS. The use of gamma-linolenic acid and linoleic acid to differentiate between temporal lobe epilepsy and schizophrenia. Prostaglandins Med 1981;6(4):375-379. PubMed
  10. Bard, J. M., Luc, G., Jude, B., Bordet, J. C., Lacroix, B., Bonte, J. P., Parra, H. J., and Duriez, P. A therapeutic dosage (3 g/day) of borage oil supplementation has no effect on platelet aggregation in healthy volunteers. Fundam.Clin.Pharmacol. 1997;1
  11. Puri BK. The safety of evening primrose oil in epilepsy. Prostaglandins Leukotrienes Essential Fatty Acids 2007;77:101-3. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Borage and Diltiazem Together: Common Questions

Is it safe to take Borage with Diltiazem?
We do not list a known interaction between Borage and Diltiazem. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Borage and Diltiazem have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Borage and Diltiazem combination checked?
Interactions in our licensed database are recorded against drug classes. Diltiazem is filed under 9 classifications, and Borage has documented interactions with 3 drug classes — none of Diltiazem's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Borage interact with any other medications?
Yes. Borage has 226 documented drug interactions in our database — Diltiazem is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Diltiazem interact with any supplements?
Yes. Diltiazem has documented interactions with 260 supplements in our database — Borage is not one of them. The Diltiazem interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Borage monograph Uses, safety profile, and every drug interaction in one place Diltiazem drug information The full plain-English guide to this medication Diltiazem supplement interactions Every supplement checked against Diltiazem, 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 References The 11 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Diltiazem and Borage?

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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.