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St. John’s wort is a common dietary supplement that you may have seen on the shelf at your local drug store. People most often use it to relieve symptoms of depression. Some studies have shown that it may be beneficial in the treatment of mild to moderate depression. But healthcare providers don’t recommend using it for various reasons.
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St. John’s wort is a plant that’s used as an herbal supplement. It’s an over-the-counter (OTC) medication. That means you don’t need a prescription from your healthcare provider. You can get it at your local drug store.
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People most commonly take St. John’s wort to treat the symptoms of depression. But healthcare providers don’t recommend using it for several reasons, including:
The St. John’s wort plant is a wild shrub. Another name for the plant is Hypericum perforatum. It has clusters of yellow flowers with five petals each. People have used the plant’s flowers and leaves for medical purposes for thousands of years. But that doesn’t mean it’s safe or effective. You should talk to your healthcare provider before taking it.
There aren’t any true St. John’s wort benefits. People take it most often to relieve symptoms of depression. Studies have suggested that the supplement may be as effective as some traditional antidepressants for treating mild to moderate depression. But other studies have found that St. John’s wort is no better than a sugar pill (placebo) for treating major depressive disorder.
Researchers haven’t studied the effectiveness of St. John’s wort at length for other symptoms and conditions. There’s not enough evidence to know if it works. But other possible St. John’s wort uses may include:
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In the U.S., preparations of St. John’s wort tablets have different amounts of the active ingredient. So if you decide to use the supplement, be careful to note how much you’re taking. 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:
St. John’s wort side effects range from mild to severe. One adverse effect is a new sensitivity to sunlight. This is especially true for people with light skin. It may also occur if you take higher doses of the supplement. You can develop a serious skin reaction to sun exposure.
Other St. John’s wort side effects may include:
Scientists know a lot about the short-term adverse effects of St. John’s wort. But they know much less about the long-term effects.
There’s no evidence that weight gain is a St. John’s wort side effect. It may help improve symptoms of depression, like loss of appetite. But it won’t cause any weight gain directly.
Healthcare providers typically don’t recommend the use of St. John’s wort for anyone. But there are some groups of people who definitely shouldn’t take it. This includes people who are:
St. John’s wort can affect the way your body processes many other common medications. It can cause serious and potentially dangerous interactions. St. John’s wort can also weaken how well other medications work. These interactions can make your medications ineffective.
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Taking St. John’s wort with other medications 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 in serotonin. This can cause a condition called serotonin syndrome. The effects of serotonin syndrome can occur within minutes or hours.
In addition to SSRIs, many other medications can have dangerous interactions with St. John’s wort. If you’re taking any of the following medications, check with your healthcare provider before you take St. John’s wort. St. John’s wort interactions include:
| Medication | Interaction |
|---|---|
| Benzodiazepines, a medication for anxiety | 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, like warfarin | Reduced amount of the blood thinner in your blood, which makes it less effective and more likely to form clots |
| Cyclosporine, a medication that prevents your body from rejecting a transplanted organ | Reduced amount of the medication in your blood, which makes it less effective, potentially causing dangerous results |
| Digoxin, a heart medication | Reduced amount of the medication in your blood, which makes it less effective, potentially causing dangerous results |
| Imatinib, a chemotherapy medication | Reduced effectiveness of the medication |
| Iron supplement | Reduced iron absorption |
| Monoamine oxidase inhibitors (MAOIs), an antidepressant | Increased effects of the MAOI, which could cause life-threatening high blood pressure |
| Non-nucleoside reverse transcriptase inhibitors, an HIV medication | Increased metabolism of the inhibitor, which can reduce its effectiveness |
| Omeprazole, an acid reducer | Decreased serum concentrations of the medication, which can reduce its effectiveness |
| Oxycodone, a pain medication | Reduced effectiveness of the medication |
| Phenytoin, an epilepsy medication | Reduced effectiveness of the medication |
| Photosensitizing medications | Increased risk of sun sensitivity |
| Protease inhibitors, an HIV medication | Reduced amounts of the inhibitor in your blood, which can reduce its effectiveness |
| Some antipsychotics, like clozapine | Reduced effectiveness of the medication |
| Tricyclic antidepressants | Reduced effectiveness of the medication |
| Medication | |
| Benzodiazepines, a medication for anxiety | |
| Interaction | |
| Reduced effectiveness in treating anxiety; increased risk of side effects, including drowsiness | |
| Birth control pills (oral contraceptives) | |
| Interaction | |
| Increased metabolism of the contraceptive, which can reduce its effectiveness | |
| Blood thinners, like warfarin | |
| Interaction | |
| Reduced amount of the blood thinner in your blood, which makes it less effective and more likely to form clots | |
| Cyclosporine, a medication that prevents your body from rejecting a transplanted organ | |
| Interaction | |
| Reduced amount of the medication in your blood, which makes it less effective, potentially causing dangerous results | |
| Digoxin, a heart medication | |
| Interaction | |
| Reduced amount of the medication in your blood, which makes it less effective, potentially causing dangerous results | |
| Imatinib, a chemotherapy medication | |
| Interaction | |
| Reduced effectiveness of the medication | |
| Iron supplement | |
| Interaction | |
| Reduced iron absorption | |
| Monoamine oxidase inhibitors (MAOIs), an antidepressant | |
| Interaction | |
| Increased effects of the MAOI, which could cause life-threatening high blood pressure | |
| Non-nucleoside reverse transcriptase inhibitors, an HIV medication | |
| Interaction | |
| Increased metabolism of the inhibitor, which can reduce its effectiveness | |
| Omeprazole, an acid reducer | |
| Interaction | |
| Decreased serum concentrations of the medication, which can reduce its effectiveness | |
| Oxycodone, a pain medication | |
| Interaction | |
| Reduced effectiveness of the medication | |
| Phenytoin, an epilepsy medication | |
| Interaction | |
| Reduced effectiveness of the medication | |
| Photosensitizing medications | |
| Interaction | |
| Increased risk of sun sensitivity | |
| Protease inhibitors, an HIV medication | |
| Interaction | |
| Reduced amounts of the inhibitor in your blood, which can reduce its effectiveness | |
| Some antipsychotics, like clozapine | |
| Interaction | |
| Reduced effectiveness of the medication | |
| Tricyclic antidepressants | |
| Interaction | |
| Reduced effectiveness of the medication |
Though not confirmed, there’s potential for St. John’s wort to treat depression. But there’s not enough evidence that shows it’s beneficial for other mental health conditions, including anxiety.
Doctors don’t prescribe St. John’s wort because research on its effectiveness is lacking. Most studies show that the supplement doesn’t work for most people. Also, research has shown that St. John’s wort can cause serious, life-threatening interactions with many other medications. Listen to your healthcare provider. Always tell them about all prescription and OTC medications you’re taking before trying St. John’s wort.
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People have been using the St. John’s wort plant (Hypericum perforatum) for medical purposes for centuries. But researchers have been studying its uses and effects for a long time, too. And they’ve found very few St. John’s wort benefits. Some studies show that it may be an effective treatment for mild to moderate depression. But the supplement can cause many dangerous interactions with other medications. If you’re thinking about trying St. John’s wort, talk to your healthcare provider first. They can tell you if it’s the right option for you.
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Last reviewed on 10/08/2025.
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