Supplement & Medication Interactions

St. John's Wort induces cytochrome P450 enzymes and P-glycoprotein, reducing plasma concentrations of SSRIs and increasing the risk of serotonin syndrome when combined due to additive serotonergic effects.

Long-term metformin use depletes vitamin B12 levels

Vitamin K directly antagonizes the anticoagulant effect of warfarin by serving as a cofactor for the gamma-carboxylation of clotting factors II, VII, IX, and X, thereby reducing warfarin's efficacy.

Calcium significantly reduces levothyroxine absorption

Iron reduces levothyroxine absorption by up to 65%

Magnesium can reduce levothyroxine absorption

Fish oil may increase bleeding risk when combined with warfarin

High-dose vitamin E may increase bleeding risk with blood thinners

Iron and zinc compete for absorption when taken together in high doses

High-dose magnesium (>142mg) can interfere with zinc absorption

Calcium inhibits iron absorption by up to 60%

Calcium can bind to certain antibiotics and reduce their absorption

High-dose calcium (>600mg) can reduce zinc absorption

Antibiotics kill probiotic bacteria, reducing their effectiveness

Magnesium is needed to convert vitamin D into its active form

Vitamin K2 helps direct calcium (mobilized by vitamin D) into bones, not arteries

Vitamin C significantly enhances non-heme iron absorption (up to 6x)

Fat from omega-3 improves fat-soluble vitamin D absorption

Piperine (black pepper extract) increases curcumin bioavailability by up to 2000%