Key takeaways:
St. John’s wort is an over-the-counter herbal supplement that’s often taken for depression symptoms. The most common St. John’s wort dosage for adults is 300 mg taken by mouth 3 times a day (i.e., 900 mg per day).
Look for a St. John’s wort product that contains 0.3% hypericin. And choose a supplement brand that has a certification from a third-party organization such as the United States Pharmacopeia (USP).
You shouldn’t take St. John’s wort without talking to your healthcare team first. It can interact with many medications and may not be a safe choice for everyone.
St. John’s wort is an over-the-counter (OTC) herbal supplement. It’s commonly taken to help with symptoms of depression.
Unlike a prescription medication, St. John’s wort isn’t FDA approved. That means there isn’t an official dosage that’s been proven safe and effective. But research offers some guidance on effective dosages and what to avoid.
So what’s the best St. John’s wort dosage to take? And what can you do to help protect your safety while taking it? Here’s what you need to know.
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What’s the typical St. John's wort dosage for adults?
In studies, the typical St. John’s wort dosage for depression symptoms in adults is 900 mg per day. To achieve this dosage, the best approach is to take 300 mg by mouth 3 times a day to minimize side effects.
You can take St. John’s wort with or without food. But taking it with meals may help reduce nausea and diarrhea, which are both common St. John’s wort side effects.
You can also start with a lower, 300 mg daily dose of St. John’s wort and increase it every few weeks to help reduce the likelihood of side effects.
St. John’s wort dosages over 1,800 mg daily aren’t recommended. Higher doses don’t seem to have a greater effect on depression symptoms. And they raise the risk of unwanted side effects and drug interactions.
Good to know: Hypericin is considered to be a main active ingredient in St. John’s wort. Most St. John’s wort dosages are based on a hypericin content of 0.3%. Keep in mind that St. John’s wort extract is typically standardized to contain this amount of hypericin. But St. John’s wort powder typically isn’t. So be sure to read product labels to ensure you’re always choosing a standardized St. John’s wort supplement with 0.3% hypericin.
How long does it take St. John’s wort to start working?
St. John’s wort may take a few weeks to start working. Some side effects may go away during this time, as your body gets used to the supplement. So it’s best to stick with your starting dosage for about 4 weeks before making any changes.
Who shouldn’t take St. John’s wort?
You shouldn’t take St. John’s wort if you’re already taking medication(s) for depression or other mental health conditions. Adding St. John’s wort could raise your risk of serotonin syndrome, a serious side effect caused by too much serotonin in the body.
St. John’s wort can also interact with many other medications. So it’s best to review your medication list with your pharmacist or prescriber before trying St. John’s wort to avoid any issues.
It’s also not recommended to treat depression or other mental health symptoms on your own with herbal supplements. The best first step is to talk to your healthcare team. They can help you make safe, informed decisions about your treatment options.
What’s the typical St. John's wort dosage for children?
There are fewer studies available on St. John’s wort for depression in children. So it’s best to talk to a pediatrician before giving it to your child.
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One small study used a St. John’s wort dosage of 150 mg three times a day in children ages 6 to 16. After 4 weeks, if symptoms didn’t improve, the dosage was increased to 300 mg three times a day.
A good approach to giving St. John’s wort to a child is to start with a low dosage and increase it after a few weeks if needed. Your child’s pediatrician can help you decide on the best St. John’s wort dosage to start with.
Tips for choosing a St. John’s wort product
St. John’s wort and other OTC supplements are less regulated than prescription medications. It’s possible for a St. John’s wort supplement to contain ingredients that aren’t listed on the label. So there are a few extra steps you should take to help protect your safety.
Look for a supplement with a verification mark from the United States Pharmacopeia (USP) or a similar independent certification group on the label. This means the supplement’s manufacturer took extra steps to ensure the quality of their product. Third-party testing for potency and purity is also a good sign of a reputable supplement company.
There are many different types of St. John’s wort dosage forms. Some of the most common are:
Tablets
Capsules
Liquids
Tea bags
Gummies
Lozenges
Most clinical studies use oral tablets or capsules. But that doesn’t mean other dosage forms aren’t equally effective. As long as a St. John’s wort supplement contains 0.3% hypericin and comes from a reputable source, you can choose whatever form you prefer. Just be sure to pay attention to the serving size on the package: You may need more than one serving to get the recommended dose.
Good to know: You can purchase St. John’s wort over the counter, but you should still let your healthcare team know you’re planning on taking it. Your prescriber and pharmacist can also help recommend a trusted brand.
Are there any dosage adjustments for medical conditions?
Often, a medical condition such as kidney or liver disease requires a change in the dose of a medication or supplement. But this doesn’t seem to be the case with St. John’s wort.
That being said, St. John’s wort interacts with a number of medications. An interaction could raise or lower the levels of your medications in your body. This could make your medications less effective or more likely to cause side effects.
Some medications that interact with St. John’s wort include:
Migraine medications
Several statins, including atorvastatin
Warfarin
Benzodiazepines, such as alprazolam
Transplant medications, such as cyclosporine
This isn’t a full list of medications that can interact with St. John’s wort. Be sure to give your prescriber or pharmacist your medication list before you start taking St. John’s wort, so they can look for potential interactions.
What happens if you miss a dose of St. John's wort?
If you miss a dose of St. John’s wort, take it as soon as you realize. But if it’s almost time for your next dose, skip the missed one and proceed with your usual schedule. Don’t double your next dose to make up for the one you missed.
What should you do if you take too much St. John's wort?
If you take an extra dose of St. John’s wort by mistake, it’s unlikely to cause an issue. You may notice more side effects, such as nausea and dizziness.
But taking a large amount of St. John’s wort can be more concerning. Taking too much St. John’s wort can lead to serotonin syndrome, which could become life-threatening if it isn’t treated quickly. Early symptoms of serotonin syndrome include sweating, confusion, and a fast heart rate.
If you or someone you know takes too much St. John’s wort, contact a healthcare professional or call Poison Control at 1-800-222-1222 for instructions. If you have serious symptoms — or your symptoms get worse — call 911 or go to the nearest emergency room right away.
Frequently asked questions
The most common St. John’s wort side effects include upset stomach, dizziness, and drowsiness. Dry mouth, trouble sleeping, and headaches are also possible. In most cases, these side effects will improve as your body adjusts to the supplement. Less common St. John’s wort side effects include sun sensitivity, eye problems, and serotonin syndrome. These are more likely if you take higher doses than recommended or combine St. John’s wort with certain medications.
St. John’s wort seems to increase levels of serotonin, norepinephrine, and dopamine in the brain. These are all chemical messengers associated with mood and motivation. St. John’s wort also has other effects on the brain that aren’t as well understood.
The most common St. John’s wort side effects include upset stomach, dizziness, and drowsiness. Dry mouth, trouble sleeping, and headaches are also possible. In most cases, these side effects will improve as your body adjusts to the supplement. Less common St. John’s wort side effects include sun sensitivity, eye problems, and serotonin syndrome. These are more likely if you take higher doses than recommended or combine St. John’s wort with certain medications.
St. John’s wort seems to increase levels of serotonin, norepinephrine, and dopamine in the brain. These are all chemical messengers associated with mood and motivation. St. John’s wort also has other effects on the brain that aren’t as well understood.
The bottom line
St. John’s wort is an over-the-counter herbal supplement that’s a common choice for depression symptoms. But it’s not an FDA-approved medication, so there’s no official recommended dosage.
In clinical studies, the most common St. John’s wort dosage for adults is 300 mg taken 3 times daily (i.e., 900 mg per day) with food. Make sure to choose a certified product with 0.3% hypericin, one of the active compounds in St. John’s wort.
Many medications interact with St. John’s wort, so you should check with your healthcare team before trying it. You also shouldn’t give it to a child without a pediatrician’s OK.
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References
Dietary Supplement Label Database. (n.d.). Search results: St. John’s wort. National Institutes of Health.
Findling, R. L., et al. (2003). An open-label pilot study of St. John’s wort in juvenile depression. Journal of the American Academy of Child and Adolescent Psychiatry.
Klemow, K. M., et al. (2011). Chapter 11: Medical attributes of St. John’s wort (Hypericum perforatum). Herbal Medicine: Biomolecular and Clinical Aspects, 2nd edition. CRC Press/Taylor & Francis.
Loria, K. (2019). How to choose supplements wisely. Consumer Reports.
Moret, C., et al. (2011). The importance of norepinephrine in depression. Neuropsychiatric Disease and Treatment.
Nicolussi, S., et al. (2020). Clinical relevance of St. John's wort drug interactions revisited. British Journal of Pharmacology.
Peterson, B., et al. (2023). St John's wort. StatPearls.
Veatch-Blohm, M. E., et al. (2021). Screening for consistency and contamination within and between bottles of 29 herbal supplements. PLOS One.
