Can I take Magnesium and St John's wort together?

Why this happens

Magnesium and St John's Wort are processed by the body through different pathways. Magnesium is a mineral primarily regulated by the kidneys, while St John's Wort affects liver enzymes (specifically CYP3A4). They do not interfere with each other's absorption or effectiveness.

What you should do

You can take these together. However, always inform your doctor or pharmacist about all supplements you are taking, as St John's Wort interacts with many prescription medicines (such as antidepressants, blood thinners, and the contraceptive pill).

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, anticoagulants (like warfarin), and anti-epilepsy drugs. Do not start this herbal remedy without a pharmacist checking your current medications.

Serotonin syndrome

Taking St John's wort with other antidepressants (such as SSRIs) can cause serotonin syndrome, a potentially life-threatening condition involving high body temperature, agitation, and muscle rigidity.

Kidney disease

If you have severe kidney problems, your body may not be able to remove excess magnesium, leading to dangerously high levels in the blood. Check with your doctor before use.

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.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol while taking St John's wort. Both substances can cause drowsiness and affect your coordination; combining them increases these effects and may impact your mental health.

It is best to avoid or strictly limit alcohol when taking magnesium. Alcohol acts as a diuretic, which can increase the amount of magnesium your body loses through urine, potentially making the supplement less effective. Additionally, chronic alcohol use can lead to magnesium deficiency.

Dairy products (Milk, Cheese, Yoghurt)

Avoid taking magnesium supplements at the same time as large amounts of dairy products. Dairy is high in calcium, and high doses of calcium can compete with magnesium for absorption in the gut, meaning you may not get the full benefit of your supplement. It is best to space them at least 2 hours apart.

Caffeine (Coffee, Tea, Energy drinks)

St John's wort can increase sensitivity to caffeine. This may lead to feelings of anxiety, restlessness, or a racing heart.

It is best to limit caffeine intake around the time you take magnesium. Like alcohol, caffeine has a mild diuretic effect and can increase the excretion of magnesium through the kidneys.

Foods high in Tyramine (Aged cheeses, cured meats, soy sauce, overripe fruits)

While rare with modern preparations, St John's wort may interact with tyramine-rich foods, potentially causing a sudden increase in blood pressure. If you experience a severe headache or chest pain after eating these foods, seek medical advice.

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.