Supplements and Diltiazem hydrochloride.
Diltiazem hydrochloride, sold under the brand names Tildiem, Adizem-XL, Slozem, Zemtard XL, Dilzem SR, Cardizem, Tiazac, is a calcium channel blocker: it relaxes vascular smooth muscle and reduces afterload.
Diltiazem hydrochloride is a calcium channel blocker. The dihydropyridine subclass (amlodipine, felodipine, nifedipine) preferentially blocks arterial L-type channels and is prescribed mainly for hypertension. Verapamil and diltiazem sit outside the dihydropyridine family. They also affect cardiac conduction and are used for arrhythmia control. CYP3A4 metabolism applies across the class, so 3A4 inhibitors (grapefruit, and certain supplements at higher doses including curcumin, quercetin, and schisandra) can raise plasma levels by 20 to 40 percent. The side effect most often reported is ankle oedema, from preferential arteriolar dilation, and it scales with dose. Additive BP supplements (beetroot, hibiscus, garlic) CoQ10 lowers systolic pressure by roughly 3 to 5 mmHg in people with cardiometabolic conditions (Zhao 2022), though a Cochrane review found no effect in primary hypertension and no study has tested it alongside a blood-pressure drug, so watch readings rather than treat it as a known interaction. stack on top. Verapamil and diltiazem carry an additional interaction with CoQ10. They have a small negative inotropic effect, and CoQ10 is sometimes said to offset it, but no trial in our database tests that.
Below are the 3 documented pairs we have explicitly assessed against Diltiazem hydrochloride in the Distil database: 3 amber. The pairs cluster around 1 mechanism: Additive blood-pressure lowering. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Last reviewed 14 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
Additive blood-pressure lowering
Amber Does Beetroot Extract interact with ?
Beetroot lowers blood pressure through the nitric oxide pathway. Diltiazem lowers blood pressure through calcium-channel blockade and also slows the heart rate. Used together, the combined blood-pressure effect tends to be larger than either alone. Watch for dizziness on standing in the first two weeks. If symptoms appear, tell your GP.
Evidence: Limited human data, based on case reports and a known mechanism.
Amber Does Melatonin interact with ?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure medicine like diltiazem this may add up to a slightly larger drop than the medicine alone. This is usually mild and often welcome, but if you notice dizziness or lightheadedness, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Spirulina interact with ?
Spirulina has a mild blood-pressure-lowering effect of its own, shown in human trials. Diltiazem lowers blood pressure through calcium-channel blockade and also slows the heart rate. Used together, the combined effect tends to be a little larger than the medicine alone. Watch for dizziness on standing in the first couple of weeks, and tell your GP if it happens so your dose can be reviewed.
Evidence: Limited human data, based on case reports and a known mechanism.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
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How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
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The free checker answers one interaction question at a time. A Distil report reviews the bigger picture: your goals, diet, medications, current supplements and any blood results you provide, then shows what appears worth keeping, changing, adding or leaving out.
- what your diet already covers, so you are not adding a capsule for something food is already handling
- which evidence-graded compounds are worth considering for your goals, and which were considered but left out
- what to keep, change or stop from what you already take, plus the order to introduce anything new
- how your medications and complete supplement stack fit together, with daily timing and a clear point for reassessment
The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
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