Vitamin D3 has 4 documented interactions in Magellan’s curated dataset, covering Thiazide diuretics, Corticosteroids (e.g. prednisone), Orlistat (fat-absorption blocker), Statins (cholesterol medications). Each entry below gives the mechanism as the cited reference states it, the direction the risk runs, how serious that reference treats it, and what to actually do about it — which is, in every case, a conversation with the clinician or pharmacist who manages the prescription rather than a decision you make alone.
What it is. Vitamin D3 (cholecalciferol) is a fat-soluble secosteroid that the skin synthesizes on exposure to ultraviolet-B light and that is also obtained from foods and supplements. It is converted in the liver to 25-hydroxyvitamin D (calcidiol), the main circulating marker of vitamin D status, and then to the active hormone calcitriol, which regulates calcium and phosphate homeostasis and bone metabolism and has broad effects on immune function.
Where it sits on the evidence. Magellan grades the supplement itself as Moderate evidence, with a typical studied dose of 800–2,000 IU/day (2,000 IU/day in the major trials); test 25(OH)D first. That grade is about whether it works, not about whether it is safe alongside your medication — the two questions are independent, and this page answers only the second.
Products this covers: Dr. Mercola Liposomal Vitamin D3.
How the risks cluster. The entries split across 2 different mechanisms — nutrient level; drug levels — and they are not managed the same way, so read each one rather than assuming a single rule covers all of them.
Safety and efficacy are separate questions, and this page only answers the first. For the second, the study Magellan’s coverage of Vitamin D3 rests on is:
“Vitamin D supplementation was associated with a reduction in cancer mortality but not all-cause or cardiovascular mortality in this meta-analysis of randomised controlled trials.”
A strong result does not make a supplement safe alongside your prescription, and a documented interaction does not mean the supplement does not work. Magellan grades those two things separately, and neither grade moves for a commission.
Magellan’s Medication Safety Check runs entirely on your device — type the medicines you take and it flags every documented interaction in this dataset. Nothing you type is sent anywhere.
Open the Medication Safety Check →Thiazides decrease urinary calcium excretion; combined with vitamin D supplements (which increase intestinal calcium absorption), this can lead to hypercalcemia, especially in older adults or those with impaired kidney function or hyperparathyroidism.
Medicines in this group include: Hydrochlorothiazide (Hctz, Microzide), Chlorthalidone (Thalitone), Indapamide (Lozol).
Corticosteroids can reduce calcium absorption and impair vitamin D metabolism; vitamin D deficiency is roughly twice as common among long-term steroid users, so vitamin D needs and status should be monitored.
Medicines in this group include: Prednisone (Deltasone), Prednisolone (Orapred, Millipred), Dexamethasone (Decadron), Hydrocortisone (Cortef), Methylprednisolone (Medrol).
Orlistat, especially combined with a reduced-fat diet, reduces absorption of vitamin D from food and supplements, which can lower blood 25(OH)D levels.
Medicines in this group include: Orlistat (Xenical, Alli).
Vitamin D and these statins compete for the same metabolizing liver enzyme; high intakes of vitamin D, especially from supplements, might reduce the potency of these particular statins.
Medicines in this group include: Atorvastatin (Lipitor), Simvastatin (Zocor), Rosuvastatin (Crestor), Lovastatin (Mevacor, Altoprev), Pravastatin (Pravachol), Pitavastatin (Livalo), Fluvastatin (Lescol).
These are the warning signs that go with the medication classes on this page. They are general safety-netting, not a prediction that any supplement will cause them.
If something feels seriously wrong, do not wait for an appointment. Call 911 (US) or your local emergency number.
Severity describes the interaction as the cited reference frames it, not how a specific person will react. A “minor” entry in someone with kidney disease, on five other drugs, can matter more than a “major” one in someone on nothing else.
This is a curated set of interactions with citations — not an exhaustive pharmacology database. An interaction that is absent here has not been ruled out; it may simply not be documented in the references Magellan curates from. Supplements are also not batch-tested for identity or contamination the way prescription drugs are, so what is on the label is a claim rather than a guarantee. And most of these entries come from case reports and mechanistic work rather than randomized trials, which is exactly why the sensible response is a pharmacist review rather than either alarm or dismissal.
5 documented interactions across 4 supplements.
43 documented interactions across 24 supplements.
9 documented interactions across 9 supplements.
5 documented interactions · shares a drug class with Vitamin D3.
5 documented interactions · shares a drug class with Vitamin D3.
4 documented interactions · shares a drug class with Vitamin D3.
4 documented interactions · shares a drug class with Vitamin D3.
The mechanism and the research behind the compound itself.
A–Z of every supplement and drug class in this dataset, plus how to read an interaction.
What the research actually shows, graded independently of affiliate commissions.
Not without checking with the prescriber or pharmacist first. Magellan's dataset grades this as a major interaction: Thiazides decrease urinary calcium excretion; combined with vitamin D supplements (which increase intestinal calcium absorption), this can lead to hypercalcemia, especially in older adults or those with impaired kidney function or hyperparathyroidism. (Source: Vitamin D - Health Professional Fact Sheet.)
4 interactions are documented in Magellan's curated dataset: 1 major, 2 moderate, 1 minor. They cover Thiazide diuretics, Corticosteroids (e.g. prednisone), Orlistat (fat-absorption blocker), Statins (cholesterol medications). Absence from this list is not proof of safety — it means no interaction is documented in the references we curate from.
Magellan lists the typical studied dose as: 800–2,000 IU/day (2,000 IU/day in the major trials); test 25(OH)D first. Dose matters for interactions — several of the entries on this page describe effects that only appear at supplemental rather than dietary intakes.