9 St. John’s Wort Side Effects to Be Aware Of
Key takeaways:
Common St. John’s wort side effects include dizziness, drowsiness, and stomach issues. Dry mouth, headache, and insomnia are also possible. These side effects are usually mild and often go away as your body adjusts to the supplement.
Sexual problems and sun sensitivity are rare, but happen in some people taking St. John’s wort. Your healthcare team can help you manage them if needed.
Serious St. John’s wort risks and side effects include allergic reactions, eye damage, and serotonin syndrome. Taking more St. John’s wort than recommended or combining it with prescription antidepressants can make these side effects more likely. So, be sure to talk with your healthcare team before taking it.
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St. John's wort is a natural supplement that’s commonly taken for mood disorders, including depression. It’s been used as a medicine for a long time — as far back as ancient Greece. But since it isn’t an FDA-approved medication, it’s hard to find reliable information about how safe or effective it is.
At the recommended dosage, St. John’s wort seems to cause less side effects than other antidepressants. But it’s still a good idea to be aware of what side effects you may experience while taking it.
Side effects at a glance
Below are the mild and serious side effects that are possible when taking St. John’s wort. Keep in mind that this isn’t a complete list. So it’s best to talk to a healthcare professional about any side effects you experience while taking this supplement, even if it isn’t listed here.
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Mild St. John’s wort side effects:
Upset stomach
Dizziness
Fatigue
Dry mouth
Headache
Anxiety or agitation
Sex-related problems
Sun sensitivity
Rare but serious St. John’s wort side effects:
Serotonin syndrome
Eye damage
Tingling or burning sensations (neuropathy)
Hallucinations (seeing things that aren’t there)
Confusion or other mental changes
Allergic reaction
Let’s take a closer look at nine St. John’s wort side effects and what to do if they happen to you.
St. John’s wort dosages: Review how much St. John’s wort is recommended and tips for choosing a high-quality supplement.
Depression treatment options: From therapy and medications to supplements and lifestyle changes — learn about the different options for treating depression.
Natural ways to fight depression: Learn about small lifestyle changes that can have a big impact on your mood.
1. Stomach issues
You may have mild to moderate gastrointestinal (GI) symptoms, such as nausea and diarrhea, while taking St. John’s wort. They likely happen because St. John increases serotonin levels in the body. Higher serotonin levels can help lessen depression symptoms, but they can cause GI side effects, too.
GI symptoms often improve as your body gets used to St. John’s wort. In the meantime, try taking it with meals to see if that helps your symptoms. You may also want to avoid spicy, fried, or high-fiber foods that can worsen your symptoms.
If these changes aren’t enough, over-the-counter (OTC) medications for upset stomach, such as bismuth subsalicylate (Pepto-Bismol), may offer temporary relief.
If your GI symptoms worsen or don’t improve, talk to your healthcare team. They may suggest a lower dose of St. John’s wort or a different medication for your symptoms.
Good to know: Severe GI symptoms could be an early sign of a more serious St. John’s wort side effect — serotonin syndrome. We’ll cover this side effect in more detail later.
2. Dizziness and drowsiness
Dizziness and drowsiness are both possible St. John’s wort side effects. You may also feel confused or disoriented in rare cases. These side effects are usually mild, and like GI symptoms, they often improve over time.
It’s a good idea to avoid driving or other activities that require coordination or mental alertness when you first start taking St. John’s wort. It’s fine to resume these activities once you know how it affects you. It’s also best to avoid alcohol or other substances that could make these side effects worse.
If the dizziness or drowsiness is severe or doesn’t improve, talk with your healthcare team. They can help you decide on the best way to manage these side effects.
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3. Dry mouth
Dry mouth is another possible side effect of taking St. John’s wort. It may improve or go away over time. You can often manage dry mouth on your own by staying hydrated, chewing sugar-free gum, or sucking on ice chips. OTC saliva substitutes are another helpful option.
Unmanaged dry mouth can lead to dental problems over time. So be sure to stay on top of your dental appointments and practice good dental hygiene if you have this side effect. Talk to your healthcare team about management options if dry mouth is an issue for you.
4. Headache
Like many medications, St. John’s wort can cause headaches for some people. Staying hydrated and avoiding triggers such as alcohol and artificial sweeteners can help prevent headaches. Managing stress is also helpful, when possible.
If needed, talk to your healthcare team about whether an OTC headache medication such as acetaminophen (Tylenol) is an option for you. And if your headache becomes severe or doesn’t go away, be sure to talk to a healthcare professional. There could be something different or more serious causing them.
5. Insomnia
Insomnia is another possible St. John’s wort side effect. This is because it acts like a stimulant for some people.
Insomnia may improve with continued use of St. John’s wort. In the meantime, be sure to practice good sleep hygiene, such as avoiding screens before bedtime. Talk to your healthcare team about a safe OTC sleep medication if needed.
If insomnia continues while taking St. John’s wort, you may need to lower your dosage or take your last dose earlier in the day. Your healthcare team can help you decide on the best course of action.
6. Anxiety
Since St. John’s wort can feel stimulating for some people, there’s also a possibility of feeling more restless during the day. You may also notice new or worsening anxiety symptoms while you’re taking it.
Limiting caffeine during the day may help lessen these symptoms. They may also improve with continued use or a lower dose of St. John’s wort.
Coping skills such as deep breathing, yoga, or taking a walk can help lessen anxiety symptoms. But if they’re bothersome let your healthcare team know. They can suggest other management options or an alternative to St. John’s wort for your symptoms.
Good to know: In rare cases, St. John’s wort may cause or worsen certain symptoms related to your mental health. This can include racing thoughts or seeing things that aren’t there. If you notice a change in your thoughts or behavior while taking St. John’s wort, seek medical care right away. It may not be the best treatment option for your symptoms.
7. Sexual problems
Mild to moderate sexual problems, such as lower sex drive or erectile dysfunction, may occur when taking St. John’s wort. Sex-related problems are common with certain prescription antidepressants. But they don’t seem to be as common with St. John’s wort. A small study comparing it to sertraline (Zoloft) showed fewer sex-related difficulties with St. John’s wort.
Speak with your healthcare team for advice or treatment options if St. John’s wort is affecting your sex life.
8. Sun sensitivity
Skin irritation and sun sensitivity are possible side effects of St. John’s wort. Sun sensitivity is more likely if you’re taking a higher dose of St. John’s wort than recommended. But even at suggested doses, it’s a good idea to wear sunscreen and limit direct sun exposure when you can. In rare cases, sun sensitivity can lead to nerve damage. This can cause a tingling or burning sensation in your skin. Seek medical care if you notice symptoms of nerve problems while taking St. John’s wort.
Some studies also show that St. John’s wort can raise your risk of eye damage from the sun. Again, this is rare, but it’s a good idea to wear UV-protective sunglasses when you’re outside while you’re taking St. John’s wort. If you notice any changes to your vision while taking St. John’s wort, seek medical care right away.
Keep in mind: An allergic reaction can sometimes look like mild skin irritation at first. If you notice raised, red bumps (hives) on your body or you have other allergy symptoms, such as itching, it’s best to see a healthcare professional. If you also have trouble breathing or your mouth or lips start to swell, get emergency help right away.
9. Serotonin syndrome
As mentioned, St. John’s wort can raise your serotonin levels. And if serotonin levels are too high, a possibly serious condition called serotonin syndrome can happen. It’s more likely if you take St. John’s wort with other medications that raise serotonin levels. This includes many antidepressants. So, if you’re taking a prescription antidepressant you shouldn’t start taking St. John’s wort without talking to your prescriber first.
Symptoms of serotonin syndrome may include:
Increased heart rate
Tremors
Sweating
Trouble sleeping
Agitation
Confusion
High blood pressure
Diarrhea
Fever
Uncontrolled movements
If you develop any of these symptoms while you’re taking St. John’s wort, get medical help right away. Serotonin syndrome can be life threatening if it isn’t treated quickly.
Other medications can raise serotonin levels, so be sure to review your full medication list with your healthcare team before you start taking St. John’s wort. This can help them spot any interactions that could make serotonin syndrome an issue for you.
Does St. John’s wort cause weight gain?
Some antidepressants can cause weight gain, but St. John’s wort doesn’t seem to be one of them. Keep in mind that in some cases, your appetite may improve as your depression symptoms lessen. So if you’re gaining weight while taking St. John’s wort, this could be part of the reason.
However, everyone responds to supplements differently. So if you notice changes in your body weight while taking St. John’s wort, it’s best to talk to a healthcare professional.
The bottom line
St. John’s wort can make you feel dizzy, drowsy, or upset your stomach — especially when you first start taking it. Dry mouth, headaches, and insomnia are also possible. Most common St. John’s wort side effects are mild and go away over a few weeks as your body gets used to it.
Other possible St. John’s wort side effects include sex-related problems and sun sensitivity. In rare cases, allergic reactions, eye damage, and serotonin syndrome can happen. Serious side effects are more likely if you take more St. John’s wort than recommended or if you take it along with other antidepressants. Be sure to talk to your healthcare team before taking St. John’s wort to make sure it’s a safe option for you.
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References
Canenguez Benitez, J. S., et al. (2022). Advantages and disadvantages of using St. John's wort as a treatment for depression. Cureus.
Ernst, E., et al. (1998). Adverse effects profile of the herbal antidepressant St. John's wort (Hypericum perforatum L.). European Journal of Clinical Pharmacology.
Institute for Quality and Efficiency in Health Care. (2023). Depression: Research summaries – Can St. John’s wort products help? InformedHealth.org.
Khalifa, S. (2015). Photodynamic sensory neuropathy in a patient treated with St John's wort. The Primary Care Companion for CNS Disorders.
Klemow, K. M., et al. (n.d.). Chapter 11: Medical attributes of St. John’s wort (hypericum perforatum). Herbal Medicine: Biomolecular and Clinical Aspects.
National Center for Complementary and Integrative Health. (2017). St. John’s wort and depression: In depth.
National Center for Complementary and Integrative Health. (2020). St. John’s wort.
National Institute of Dental and Craniofacial Research. (2022). Dry mouth.
Peterson, B., et al. (2023). St. John's wort. StatPearls.
Van Gurp, G., et al. (2002). St John’s wort or sertraline? Canadian Family Physician.
