St. John's Wort

What St. John’s wort is

St. John’s wort is a flowering plant that has been used in traditional remedies for a very long time. Today it is sold as a supplement, usually in capsules, tablets, teas, or liquid extracts, and it is most often promoted for low mood and mild depression. Like other supplements, it is not reviewed by the FDA the way prescription medicines are, and the actual amount of active ingredient can vary quite a bit from one product to the next.

This page is general education about St. John’s wort, not a recommendation that you should or should not take it. Of all the supplements people ask about, this is one of the most important to talk through with your clinician first, because of how strongly it interacts with prescription medicines.

What it is used for

The main reason people reach for St. John’s wort is low mood. Here the evidence is more encouraging than it is for most supplements: for mild to moderate depression, studies suggest it tends to do better than a placebo and can work about as well as some standard antidepressants. That is a genuinely unusual thing to be able to say about a supplement, so it is worth being honest about it.

The honesty cuts both ways, though. For more severe depression, and for use beyond a few months, it is much less certain that it helps. It has also been looked at for things like menopausal hot flashes and a handful of other conditions, where the evidence is thin. And the catch that matters most is not about whether it works: it is that the safer-sounding “natural” label hides a serious interaction problem, which makes treating yourself with it riskier than it appears. If low mood is what you are dealing with, it is worth looking at the whole picture together, including guides like depression and anxiety.

How it might work

St. John’s wort is thought to act on some of the same brain chemicals involved in mood, including serotonin, which is part of why it gets compared to antidepressants. The exact way it works is not fully pinned down, and that same activity on serotonin is also what makes combining it with certain medicines risky. As with any supplement, how much it helps a given person, if at all, is individual, and plausible is not the same as proven.

How people take it

There is no single standard way to take St. John’s wort, and because products differ so much, this is not something to figure out from a label alone. A few general points apply:

• Do not start it on your own if you take any prescription medicine. The interactions are the main event here, and they are easy to miss. Check first.
• Products are not all the same. The strength and the actual content vary between brands, so two bottles labeled the same way are not necessarily equivalent.
• Do not stop or start it abruptly around other treatment. Because it changes how your body handles many drugs, both starting and stopping it can shift your other medicine levels.
• Bring it up before any surgery or new prescription, so it can be accounted for.

What to expect

If St. John’s wort is going to help low mood, the change tends to be gradual rather than sudden, the way it is with antidepressants, so it would not be a same-day effect. More to the point, what to expect depends heavily on what else you take, which is why the conversation before starting matters more here than with most supplements. If you and your clinician decide it is reasonable to try, pay attention to how you actually feel and keep the plan under review. As always, this is case by case.

Possible side effects

Most people who take St. John’s wort on its own tolerate it, and the everyday side effects are usually mild. The lists below are possibilities, not certainties.

Possible more common side effects:

• Stomach upset
• Trouble sleeping, restlessness, or feeling on edge
• Dizziness
• Tingling skin
• Dry mouth

One side effect worth singling out is increased sensitivity to sunlight: St. John’s wort can make your skin burn or react more easily in the sun, so sun protection matters more while taking it.

Less common, but concerning signs that could need urgent care:

• Signs of an allergic reaction: rash, hives, or swelling of the face, lips, tongue, or throat
• A severe skin or sunburn-like reaction after being in the sun
• Signs that serotonin has been pushed too high, especially if you also take an antidepressant or other serotonin-raising medicine: agitation or confusion, a fast heartbeat, fever, heavy sweating, shivering, muscle twitching or stiffness, or diarrhea

For any of these, use the help options at the bottom of this page: call 911 or go to the nearest emergency department for a medical emergency or severe reaction, or call or text 988 for a mental health crisis.

Interactions and safety

This is the part that matters most, and the reason St. John’s wort is in a different category from gentler supplements. It speeds up how your body clears a wide range of medicines, which quietly lowers their levels and can make them stop working. The list of medicines it can weaken is long and includes:

• Hormonal birth control, which can become less reliable, raising the risk of an unintended pregnancy
• Some antidepressants
• Blood thinners such as warfarin
• Anti-rejection medicines for transplants, such as cyclosporine
• Certain heart medicines, including digoxin
• Some seizure medicines
• Certain HIV and cancer medicines
• Some cholesterol medicines

On top of that, combining St. John’s wort with antidepressants or other serotonin-raising medicines can push serotonin too high, which can become a serious, even dangerous reaction rather than a minor one. There are also reports of it worsening symptoms in people who have bipolar disorder or schizophrenia, and it is not considered safe in pregnancy or while breastfeeding.

The single most useful thing you can do is tell your clinician and pharmacist everything you take, including supplements and anything you are only thinking about starting. With St. John’s wort in particular, that one step is what keeps a hidden interaction from becoming a real problem, and it lets us decide together whether it has any place in your plan.

When to contact your clinician

For routine questions, mild side effects, or whether St. John’s wort fits with the rest of your plan, send a message through the patient portal or bring it to your next visit. These are part of your ongoing care and are answered in the normal course of a few business days, so they are best for things that are not urgent.

If something feels urgent, you do not need to wait for a reply. Treat the serotonin-related warning signs above as an emergency: call 911 or go to the nearest emergency department, especially if you also take an antidepressant. Use 988 any time for a mental health crisis or thoughts of self-harm.

Questions to ask your clinician

• Given the medicines I already take, is St. John’s wort safe for me at all?
• Could it make my birth control, or any of my other medicines, less effective?
• I take an antidepressant; what is the risk of combining them?
• If I want to address low mood, what options would you suggest instead?
• What warning signs should make me stop it and call you?