9 Unknown Side Effects Of St. John’s Wort

Written by , B.Desgn, ISSA Certified Specialist In Fitness & Nutrition Tanya Choudhary B.Desgn, ISSA Certified Specialist In Fitness & Nutrition twitter_icon Experience: 2 years

“All Natural.”

The so claimed ‘100% authentic’ nature is what makes any herbal product so popular. Just put this label on any particular product (medicines or otherwise) and watch it grow in popularity firsthand. Same is the case with over-the-counter St. John’s Wort medicines too.

But does it mean that natural products mean safe? Let’s find out.

Safety Concerns Of St. John’s Wort

While natural herbs like the one in question are appealing, their usage has always been under the safety radar. In fact, herbal supplements are not regulated by The Food and Drug Administration (FDA), like their over-the-counter and prescribed medicines counterparts. For this reason, you might be at the risk of some potentially harmful herbs that are available in every pharmacy and store.

The side effects of st john’s wort are particularly common as it is an antidepressants. According to a study published in Clinical and Experimental Pharmacology and Physiology, an unprescribed and uncontrolled dosage of St. John’s Wort can have a lot of adverse reactions (1). Have a look at side effects of st johns wort:

The Side Effects Of St John’s Wort

  1. Can Interfere With Your Medication
  2. Can Elevate Blood Pressure
  3. Should Not Be Taken By Pregnant And Breastfeeding Women
  4. Should Be Avoided By People Who Are Photosensitive
  5. Should Not Be Used To Treat Severe Depression
  6. Can Make Birth Control Pills Ineffective
  7. Can Worsen Mental Disorders
  8. May Cause Excessive Hair Loss
  9. Can Cause Tissue Rejection

1. Can Interfere With Your Medication

side effects of st john's wort
Image: Shutterstock

The first and the primary concern regarding this particular herb is its interference with several medicines.

St. John’s wort induces the body to produce enzymes that help clean the bloodstreams faster, making them devoid of certain chemicals. This process, called enzyme induction, is the one that robs medicines of their power. This herb, like fluoxetine, inhibits the reuptake of the essential hormone serotonin.

Sadly, St. John’s wort interferes with the working of a number of common pharmaceuticals too (2).

It is known to interact with its prescribed antidepressants, oral contraceptives, anticoagulants, anti-seizure medicines, anti-rejection drugs, heart and cancer medications.

Note: Since this herb can interfere with medicines that are used during surgery, it is advisable to stop its intake at least a week before your surgery is scheduled. 

Prevention Method

Avoid taking St. John’s Wort if you are already taking other medicines, especially antidepressants, oral contraceptives, anti-seizure drugs etc. In case there is a need, check with your doctor before taking any action.

2. Can Elevate Blood Pressure

St. John’s wort, when combined with Monoamine Oxidase (MAO) and Selective Serotonin Reuptake Inhibitors (SSRIs), can lead to an elevated blood pressure, eventually resulting in a stroke. An overdose of this medication can even make way for serotonin syndrome (3). This particular disorder is characterized by confusion, agitation, shivering, fever, a rapid heart rate, diarrhea, muscle spasms, and perspiration.

Prevention Method

If you are under blood pressure medication or have issues related to elevated blood pressure levels, please avoid this medicine.

3. Should Not Be Taken By Pregnant And Breastfeeding Women

Pregnant ladies and breastfeeding moms should avoid taking St. John’s wort.

Due to its adverse reactions on the brain neurochemistry and hormonal balance, it’s possible that an unprescribed dosage of St. john’s wort can harm the baby.

Prevention Method

If you are pregnant or are breastfeeding, avoid this medication.

4. Should Be Avoided By People Who Are Photosensitive

side effects of st john's wort
Image: Shutterstock

This herb should totally be avoided by those who are naturally photosensitive as its usage can intensify the effect.

Using St. John’s wort makes you hyper-sensitive to sunlight. This condition is scientifically called photodermatitis. The problem elevates if you take this herb along with medicines known to increase sun-sensitivity, like sulfa drugs, piroxicam (an anti-inflammatory medication), omeprazole (Prilosec), and lansoprazole (Prevacid). In fact, a prolonged usage of St. John’s wort is also linked with the increased risk of sun-induced cataract (4).

Prevention Method

People with photosensitive skin must avoid this medication. Ideally, also take precautions (like wearing a sunscreen) as you are exposed to the sun. You should also entirely avoid tanning beds and sunlamps.

5. Should Not Be Used To Treat Severe Depression

While popular for its use in the treatment of depression, St. John’s wort shouldn’t be used if the situation is quite serious. This is valid when your depression has started meddling with your daily life, or if you are having suicidal thoughts. The risk of mania is reported to be particularly high in those battling severe depression and are on St. John’s Wort (5).

The correct method is to see a doctor immediately and have the right diagnosis, instead of relying on this herb to do its magic.

Prevention Method

If you are suffering from chronic depression, the first thing you must do is visit a counselor or a doctor. Taking medications for severe cases of depression may not help, and instead could be detrimental.

6. Can Make Birth Control Pills Ineffective

Those on contraceptives should totally avoid using St. John’s wort. There have been several cases of excessive bleeding and nausea in women on birth control pills who were taking this herb too. They also make these oral pills ineffective, which might lead to unwanted pregnancies (6).

Prevention Method

If you are on contraceptives, avoid St. John’s Wort as it might make them ineffective.

7. Can Worsen Mental Disorders

St. John’s wort, when taken with methylphenidate, is known to make the symptoms of ADD and ADHD worse. Its regular usage also contributes to the added risk of psychosis in those who have schizophrenia. It can also contribute to dementia in people who are victims of Alzheimer’s disease (7).

Additionally, this herb is particularly harmful if you have bipolar disorder.

Prevention Method

If you are suffering from ADD or ADHD, stay away from using St. John’s Wort, as the medication might aggravate the condition.

8. May Cause Excessive Hair Loss

side effects of st john's wort
Image: Shutterstock

Regular usage of St. John’s wort is known to cause excess hair loss, just like several other antidepressants (8).

Prevention Method

If your hair is thinning and are suffering from hair loss due to any reason, avoid St. John’s Wort and consult your doctor immediately.

9. Can Cause Tissue Rejection

Taking St. John’s wort can be extremely dangerous for those undergoing organ transplants.

In several cases, self-medication with this herb has led to a severe drop in the plasma levels of the cyclosporine (immunosuppressant), causing tissue rejection (9).

Prevention Method

The best solution is to consult your doctor and get your dosage described before you start taking this herb.

So, this was about side effects of st john’s wort, now look into the foods to avoid while taking st, john’s wort.

Foods To Avoid When Taking St. John’s Wort

They say Precaution is better than cure which is quite true when it comes to herbal medications such as St. John’s Wort.

You should totally avoid the following food and beverage items when you are on St. John’s wort:

  • Coffee/tea
  • Chocolate
  • Wine
  • Beer
  • Fava beans
  • Salami
  • Smoked/pickled foods
  • Yogurt
  • Cheese
  • Overripe avocados
  • Aged meats

Recommended Dosage Of St. John’s Wort

The question that arises is how much is too much? This is quite valid when it comes to any of the herbal medicines.

Here’s the recommended dosage list for this herb for consumption by adults, kids and young adults (10):

Children and young adults (>18 years)

  • For ADHD- 300 mg St. John’s wort, three times daily for eight weeks.
  • For Depression- 150-1800 mg St. John’s wort, three times daily for eight weeks.


  • For anxiety—900 mg St. John’s wort, twice daily for twelve weeks
  • For cancer—0.05-0.50 mg per kg of hypericin, for two months
  • For mild to moderate depression—20-1800 mg St. John’s wort, three times for 4 to 52 weeks
  • For severe depression—900-1800 mg, once daily for 8 to 12 weeks
  • For Obsessive-Compulsive Disorder (OCD)—450-1800 mg, once daily for 12 weeks
  • For menopausal symptoms—300 mg, three times daily for 12 weeks
  • For premenstrual syndrome (PMS)—300-900 mg daily for two menstrual cycles
  • For smoking cessation—300 mg, once or twice daily for three months

While herbal medicines attract attention and boast of its natural properties, it’s always safe to know about the pros and cons of taking an unprescribed medication. Just like we learnt how our preferred antidepressant comes with a number of fatal st johns wort side effects too.

Do you use St. John’s wort? Were you aware of any of the above st john’s wort side effects? Share your comments and feedback in the comments box below.

Stay fit, stay healthy!

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Tanya Choudhary

Tanya ChoudharyHealth & Wellness Writer

Tanya is an ISSA certified Specialist in Fitness & Nutrition. She specializes in writing articles on ingredients that benefit skin, hair, and health. She believes in the right health and lifestyle practices and strives to promote the same to everyone around her.
Read full bio of Tanya Choudhary

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