St. John's Wort may increase vitamin D metabolism, potentially reducing its effectiveness.
St. John's Wort induces CYP3A4 and CYP24A1, enzymes involved in vitamin D catabolism.
Monitor vitamin D levels if taking St. John's Wort long-term. You may need a higher dose.
Known drug category interactions for these supplements. Especially relevant if you take prescription medications.
Combining St. John's Wort with SSRIs can cause serotonin syndrome, a potentially life-threatening condition.
NEVER combine St. John's Wort with SSRIs, SNRIs, or MAOIs. Wait at least 2 weeks after stopping an SSRI before starting St. John's Wort.
St. John's Wort reduces the effectiveness of hormonal birth control, potentially causing contraceptive failure.
Use a non-hormonal backup contraceptive method while taking St. John's Wort and for one month after stopping.
St. John's Wort significantly reduces warfarin blood levels, potentially causing blood clots.
Do not take St. John's Wort while on warfarin. If already taking both, do not stop St. John's Wort abruptly — consult your doctor.
Reference values for safe daily intake of these supplements.
Risk of hypercalcemia at very high doses.