Interactions

Possible interactions include:

• Aluminum. Taking vitamin D and aluminum-containing phosphate binders, which may be used to treat high serum phosphate levels in people with chronic kidney disease, might cause harmful levels of aluminum in people with kidney failure in the long term.
• Anticonvulsants. The anticonvulsants phenobarbital and phenytoin (Dilantin, Phenytek) increase the breakdown of vitamin D and reduce calcium absorption.
• Atorvastatin (Lipitor). Taking vitamin D might affect the way your body processes this cholesterol drug.
• Calcipotriene (Dovonex, Sorilux). Don't take vitamin D with this psoriasis drug. The combination might increase the risk of too much calcium in the blood (hypercalcemia).
• Cholestyramine (Prevalite). Taking vitamin D with this cholesterol-lowering drug can reduce your absorption of vitamin D.
• Cytochrome P-450 3A4 (CYP3A4) substrates. Use vitamin D cautiously if you're taking drugs processed by these enzymes.
• Digoxin (Lanoxin). Avoid taking high doses of vitamin D with this heart medication. High doses of vitamin D can cause hypercalcemia, which increases the risk of fatal heart problems with digoxin.
• Diltiazem (Cardizem, Tiazac, others). Avoid taking high doses of vitamin D with this blood pressure drug. High doses of vitamin D can cause hypercalcemia, which might reduce the drug's effectiveness.
• Orlistat (Xenical, Alli). Taking this weight-loss drug can reduce your absorption of vitamin D.
• Thiazide diuretics. Taking these blood pressure drugs with vitamin D increases your risk of hypercalcemia.
• Steroids. Taking steroid mediations such as prednisone can reduce calcium absorption and impair your body's processing of vitamin D.
• Stimulant laxatives. Long-term use of high doses of stimulant laxatives can reduce vitamin D and calcium absorption.
• Verapamil (Verelan, Calan SR). Taking high doses of vitamin D with this blood pressure drug can cause hypercalcemia, and might also reduce the effectiveness of verapamil.