Can I take St John's wort and Vitamin D together?

Why this happens

St John's Wort is a 'liver enzyme inducer'. It speeds up the proteins (specifically CYP3A4) in your liver that break down medications and vitamins. This causes Vitamin D to be cleared from your system much faster than normal.

What you should do

If you are taking both, you should speak to your GP. They may want to monitor your Vitamin D levels with a blood test or suggest increasing your Vitamin D dose. Do not stop taking prescribed medication without consulting your doctor first.

Important precautions

Depression and Mental Health

Like other antidepressants, St John's wort may increase the risk of suicidal thoughts or self-harm, particularly when first starting treatment. Seek immediate medical help if your mood worsens.

Drug Interactions

St John's wort significantly reduces the effectiveness of many essential medicines, including the contraceptive pill, blood thinners (warfarin), epilepsy medications, and organ transplant drugs. Do not start it without a pharmacist checking your current medications.

Serotonin Syndrome

Taking St John's wort with other antidepressants or triptans (for migraine) can cause serotonin syndrome, a potentially life-threatening condition involving high fever, agitation, and muscle rigidity.

Photosensitivity

St John's wort can make your skin significantly more sensitive to sunlight, leading to severe sunburn or skin reactions even with limited exposure.

Hypercalcaemia (high blood calcium)

Do not take vitamin D if you have high levels of calcium in your blood or urine, as it can lead to serious kidney damage and heart rhythm problems.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol while taking St John's wort. Combining the two can increase drowsiness and dizziness, and may worsen the side effects of the herbal remedy.

Caffeine (Coffee, Tea, Energy Drinks)

St John's wort can sometimes increase sensitivity to caffeine, leading to feelings of restlessness, anxiety, or a racing heart. Monitor your intake if you feel jittery.

Foods high in Tyramine (e.g., aged cheeses, cured meats, soy sauce, marmite, overripe fruit)

While less common than with older prescription antidepressants, St John's wort can potentially interact with tyramine-rich foods, leading to a sudden, dangerous increase in blood pressure (hypertensive crisis). You should consume these foods in moderation.

High-fat meals

Vitamin D is a fat-soluble vitamin. It is best absorbed by your body when taken with a meal that contains some fat (such as eggs, avocado, nuts, or dairy).

Using other medicines

Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.

Disclaimer

This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.