Know2eat

St John’s wort

Hypericum perforatum

Herbs & Botanicals

What st john’s wort may help with

Ranked by how strong the human evidence is — best supported first.

Best supportedMoodStrong evidence· 2 sources

Then, in order

About St John’s wort

A flowering-top extract standardised to hypericin or hyperforin, used for depressive symptoms. It is a licensed medicine in parts of Europe and a supplement in the US.

This is the most pharmacologically active plant in the catalogue and the most dangerous to combine with medication. Its efficacy in mild to moderate depression is supported by a large Cochrane review of dozens of trials; its hyperforin content is also a powerful inducer of CYP3A4 and P-glycoprotein, which reduces blood levels of a long list of critical medicines. Both facts are true at once, and the second is the reason it is not a casual purchase.

Sold as
Standardised extract tablet, Capsule, Tincture, Tea, Oil (topical)
Standardised to
Trials use extracts standardised to 0.3% hypericin, or to 3–5% hyperforin — a product without this marker may not resemble what was studied.
Also known as
Hypericum, Klamath weed, Tipton weed

Regulation: A licensed medicine for depression in Germany and several other European countries, and an over-the-counter supplement in the US and UK. Regulators in multiple countries have issued formal warnings about its interactions with contraceptives, immunosuppressants and antiretrovirals.

What the research used

The amounts, forms and durations published trials of St John’s wort actually administered.

These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.

  • Studied for Mild to moderate depressive symptoms

    300–1800 mg

    Moderate

    Standardised extract, usually 300 mg three times daily · 0.3% hypericin in most trials · 4–12 weeks

    The trials are numerous but heavily concentrated in German-speaking countries, and studies run there report larger effects than trials elsewhere. Extracts differ in hyperforin content, which drives both the effect and the drug interactions.

This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.

None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.

  • Split through the day

    Limited

    Trials dosed three times daily, following the short half-life of hyperforin. Once-daily extended formulations exist but head-to-head timing comparisons are lacking.

    Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.

  • With food

    Not enough

    Commonly taken with food for tolerability. Absorption with and without food has not been meaningfully compared.

    Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.

The evidence in depth

Best supported: Strong

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.

Mood

Mental Wellbeing
Strong evidence

A large body of randomised trials, summarised in systematic reviews, finds St John’s wort superior to placebo and broadly comparable to standard antidepressants for mild to moderate depressive symptoms, with fewer reported side effects. Trials from German-speaking countries report larger effects than those elsewhere, and it has not been shown useful in severe depression. Depression needs clinical assessment, and this is not a self-directed substitute for it.

What may be going on: Hyperforin inhibits reuptake of serotonin, noradrenaline and dopamine, which is also why serotonin syndrome is a real risk in combination with antidepressants.

Strong evidence. Consistent findings across multiple good-quality human studies.

View the 2 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Menopausal symptoms

Women's Health
Limited evidence

Some trials report reduced hot flush frequency, often as part of a combination with black cohosh. Trials are small and the interaction risks apply regardless of what it is being taken for.

Limited evidence. Early human work, or mostly lab and animal research.

View the 2 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Stress and anxiety

Mental Wellbeing
Not enough evidence

Evidence is limited for St John’s wort and anxiety disorders specifically. Most trials measured depressive symptoms, on scales where anxiety items are only a component.

Not enough evidence. Not enough human research to say anything useful yet.

View the 1 source

Deep research mode adds each paper’s own conclusion and stated limitations.

Things to know

Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.

  • Interaction

    Reduces the effectiveness of hormonal contraception

    Interacts withCombined oral contraceptives, progestin-only contraceptives, implants

    By inducing CYP3A4, St John’s wort lowers blood levels of ethinylestradiol and progestins. Breakthrough bleeding and unintended pregnancies have been reported. Anyone relying on the pill, patch, ring or a hormonal implant needs to know this before starting it.

  • Interaction

    Transplant rejection risk with ciclosporin and tacrolimus

    Interacts withCiclosporin, tacrolimus, sirolimus, everolimus

    St John’s wort dramatically lowers ciclosporin and tacrolimus levels, and acute graft rejection has been documented in transplant recipients who started it. It is contraindicated after organ transplantation.

  • Interaction

    Loss of HIV and hepatitis antiviral control

    Interacts withIndinavir and other protease inhibitors, nevirapine, efavirenz, some direct-acting antivirals

    Blood levels of protease inhibitors and of the non-nucleoside class of transcriptase inhibitors fall substantially, risking viral rebound and resistance. Regulators have issued explicit warnings against the combination.

  • Interaction

    Serotonin syndrome with antidepressants and triptans

    Interacts withSSRIs, SNRIs, MAO inhibitors, tramadol, triptans, linezolid

    Combining it with SSRIs, SNRIs, MAO inhibitors, tramadol or triptans can produce serotonin syndrome — agitation, tremor, fever, rapid heart rate and, in severe cases, death. Overlapping with an existing antidepressant is not safe without prescriber supervision.

  • Interaction

    Warfarin, digoxin, statins, anticonvulsants and chemotherapy

    Interacts withWarfarin, digoxin, simvastatin, carbamazepine, phenytoin, irinotecan, imatinib

    The same enzyme induction lowers levels of warfarin, digoxin, some statins, anticonvulsants including carbamazepine and phenytoin, theophylline, and chemotherapy agents such as irinotecan and imatinib. Effects persist for one to two weeks after stopping, so the risk continues past the last dose.

  • Worth knowing

    Photosensitivity, mania and surgery

    Hypericin causes dose-related photosensitivity, with severe sunburn reported in fair-skinned users. Manic episodes have been triggered in people with bipolar disorder. Anaesthetists advise stopping at least five days before surgery because of interactions with anaesthetic agents and cardiovascular drugs.

Evidence ratings on this page: 1 strong evidence, 1 limited evidence, 1 not enough evidence.

Supplements are sold in the US without pre-market review of efficacy or safety. Nothing on this page is a recommendation to take St John’s wort, or a dose to follow.