St John's Wort

St. John’s wort is a plant most often used to treat depression. Previous studies had shown it was effective in treating mild depression. But healthcare providers don’t recommend using it for various reasons. St. John’s wort can have dangerous effects when combined with other medications.

What is St. John’s wort?

St. John’s wort (hypericum perforatum) is a dietary supplement that people have used for the potential treatment of depression. However, healthcare providers don’t recommend using the herbal supplement for various reasons, including:

  • Limited and inconsistent evidence of effectiveness.
  • Variability of available products on the market.
  • Lack of regulation of herbal supplements in the U.S.
  • Potential for interactions with other medications.

The St. John’s wort plant is a wild shrub with clusters of yellow flowers with five petals. It gets its name from St. John the Baptist because the flowers bloom around June 24, his birthday. “Wort” is an old English term for plant. People have used both the plant’s flowers and leaves for medical purposes for thousands of years.

Previously, studies had suggested that St. John’s wort was as effective as standard antidepressants for treating mild depression. However, more recent studies have found that St. John’s wort is no better than a sugar pill (placebo) for treating moderate to severe depression.

Depression is a serious illness. You shouldn’t use St. John’s wort in place of traditional healthcare. If you or someone you know has symptoms of depression, make an appointment with a healthcare provider. You shouldn’t try to treat your condition on your own.

Dietary supplements such as St. John’s wort can affect the way your body processes many other medications. They can cause serious medical issues. In some cases, they can be dangerous or even lead to death. In addition, the U.S. Food and Drug Administration doesn’t standardize the regulation of herbal products. So, you should talk to your provider before taking St. John’s wort.


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What is St. John’s wort used for?

Scientists haven’t proven any potential St. John’s wort benefits. People take St. John’s wort most often to relieve symptoms of mild to moderate depression. But studies on the use of St. John’s wort for depression have been mixed.

Past studies had shown that people with symptoms of mild depression could benefit from the herb. But newer studies haven’t proven the effectiveness of St. John’s wort in treating mild to moderate depression. And no studies have shown that St. John’s wort is effective in treating severe depression.

The effectiveness of the herb in treating other conditions hasn’t been studied at length. There’s not enough evidence to know if it works for these conditions. But other possible St. John’s wort uses may include:

  • Relief of menopausal symptoms, such as hot flashes.
  • Treatment of insomnia, when you take St. John’s wort before bed.
  • Assistance with wound healing, when you apply lotion directly onto your skin (topically).
  • Management of nerve pain (neuralgia), when you apply St. John’s wort oil directly to your skin.

How much St. John’s wort should I take?

Preparations in the U.S. have different amounts of the active ingredient. So, if you decide to take St. John’s wort, be careful to note how much you're getting in your tablets. The most common dosage of St. John’s wort is 300 to 400 milligrams (mg) taken three times a day with meals. Beyond tablets, people also use:

  • Tinctures, teas or liquid extracts.
  • Ointments or gels.
  • Oils and lotion.


How long does St. John’s wort take to work?

Depending on which form you take, you may not feel the full effects of St. John’s wort for two to six weeks. Again, evidence hasn’t proven that the supplement works, so you may not feel any effects at all. It’s best to talk with your healthcare provider to figure out what will work best for you.

St. John’s Wort may cause a serious skin reaction to sun exposure. Other side effects range from fatigue to sexual dysfunction.

Taking St. John’s wort may cause a variety of side effects.

What are the side effects of St. John’s wort?

St. John’s wort may cause increased sensitivity to sunlight. This is especially true for people with fair skin and/or when you take the supplement in large doses. You may develop a serious skin reaction to sun exposure. Other St. John’s wort side effects may include:

  • Upset stomach.
  • Dizziness.
  • Confusion.
  • Fatigue.
  • Dry mouth.
  • Frequent urination.
  • Swelling.
  • Sexual dysfunction.
  • Increased blood pressure.
  • Fast heartbeat.

There’s no evidence that St. John’s wort causes weight gain. It may help improve symptoms of depression such as decreased appetite, but it won’t cause any weight gain directly.

Scientists know a lot about the short-term effects of St. John’s wort. However, they know much less about its long-term effects.


Is St. John’s wort safe?

According to some studies, taking an oral supplement of St. John’s wort for up to 12 weeks has proven to be safe for some people. Research hasn’t shown if the supplement is safe beyond 12 weeks of use. In addition, there’s not enough evidence to declare that using St. John’s wort directly on your skin is safe.

People who shouldn’t take St. John’s wort

There are some groups of people who shouldn’t take any form of St. John’s wort. This includes people who are:

  • Pregnant: Don’t take St. John's wort if you’re pregnant. It’s been shown to increase the muscle tone of your uterus during pregnancy. This could cause an increased risk of miscarriage. It has also caused congenital (present at birth) conditions in animal studies.
  • Breastfeeding (chestfeeding): If you’re taking St. John’s wort and nursing, your baby may experience fussiness, colic and drowsiness.
  • Taking certain medications: St. John’s wort interacts with many different drugs. The supplement may not be safe for you if you take certain prescription medications.
  • Having surgery: You shouldn’t take St. John’s wort within five days of any planned surgical procedures because of the risk of medication interactions.

Do I need to worry about any interactions while taking St. John’s wort?

St. John’s wort can affect the way many different medications work. It can cause very serious and potentially dangerous interactions with many common drugs. St. John’s wort can also weaken how well other drugs work. These interactions can make your medications ineffective.

Taking St. John’s wort with other drugs that affect your serotonin levels can be especially dangerous. Serotonin is a brain chemical produced by your nerve cells. Certain antidepressants called selective serotonin reuptake inhibitors (SSRIs) work to increase the amount of serotonin in your brain.

Mixing St. John’s wort and SSRIs can lead to a life-threatening increase of serotonin. This can cause a condition called serotonin syndrome. The effects of serotonin syndrome can occur within minutes or hours. These symptoms may include:

  • Fast heartbeat.
  • High blood pressure.
  • Increased body temperature.
  • Hallucinations.

In addition to SSRIs, many other drugs can have dangerous interactions with St. John’s wort. If you’re taking any of the following medications, don’t take St. John’s wort. St. John's wort interactions include:

Some antipsychotics, such as clozapine.
Reduced effectiveness of the antipsychotic.
Reduced effectiveness in treating anxiety; increased risk of side effects, including drowsiness.
Birth control pills (oral contraceptives).
Increased metabolism of the contraceptive, which can reduce its effectiveness.
Blood thinners such as warfarin.
Reduced blood levels of the blood thinner, which makes it less effective and more likely to form clots.
Cyclosporine, a drug that prevents your body from rejecting a transplanted organ.
Reduced blood levels of the drug, which makes it less effective, potentially causing dangerous results.
Digoxin, a heart medication.
Reduced blood levels of the drug, which makes it less effective, potentially causing dangerous results.
Imatinib, a chemotherapy drug.
Reduced effectiveness of the drug.
Reduced iron absorption.
Monoamine oxidase inhibitors (MAOIs).
Increased effects of the MAOI, which could cause life-threatening high blood pressure.
Non-nucleoside reverse transcriptase inhibitors.
Increased metabolism of the inhibitor, which can reduce its effectiveness.
Decreased serum concentrations of the drug, which can reduce its effectiveness.
Oxycodone, a pain medication.
Reduced effectiveness of the drug.
Reduced effectiveness of the drug.
Photosensitizing drugs.
Increased risk of sun sensitivity.
Protease inhibitors, which are used to treat human immunodeficiency virus (HIV) infections.
Reduced blood levels of the inhibitor, which can reduce its effectiveness.
Tricyclic antidepressants.
Reduced effectiveness of the drug.

A note from Cleveland Clinic

Depression is a very serious illness. If you or someone you know have symptoms of depression, don’t try to treat the condition on your own. Make an appointment with a healthcare provider. While some studies show that St. John’s wort may be safe and effective for the treatment of mild to moderate depression, the supplement can have many dangerous interactions with other medications.

Your provider can tell you if St. John’s wort is the right option for you. They may have other complementary healthcare approaches you can take that don’t include prescription medication. They’ll work with you to help you make a well-informed decision that’s the best option for you.

Medically Reviewed

Last reviewed on 11/29/2022.

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