St. John's Wort: Depression Evidence and Interactions
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St. John's Wort: half-life, strengths and approval status

Status · Approval status · Half-life notes

What is St. John's Wort?

St. John's wort (Hypericum perforatum) is a yellow-flowered plant sold as an herbal supplement, mostly for symptoms of depression. NCCIH says it may help mild or moderate depression, but it is clearly shown to interact in dangerous, sometimes life-threatening ways with many medicines.

Also known as: St John's wort, Hypericum perforatum, hypericum.

Reference amounts

St. John's wort has no intake value or upper limit, and NCCIH gives no standard amount. NCCIH says it appears safe for up to 12 weeks for most adults who take no medicines, and some studies suggest it can be used safely for a year or more.

Approval status and how it is used

It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.

What NCCIH says: St. John's wort appears to work better than placebo and as well as standard antidepressants for mild or moderate depression; it is uncertain whether that holds for severe depression or for longer than 12 weeks. Small studies suggest it may help menopause hot flashes and somatic symptom disorder. Depression can be serious; if you or someone in your family may have it, see a health care provider.

Interactions are the main risk. NCCIH says St. John's wort can weaken the effects of many medicines, including:

  • some antidepressants, including amitriptyline and bupropion
  • birth control pills
  • cyclosporine, which prevents rejection of transplanted organs
  • some seizure drugs, including phenytoin and carbamazepine
  • some heart drugs, including digoxin and ivabradine
  • some HIV drugs, including indinavir and nevirapine
  • some cancer drugs, including irinotecan, imatinib and docetaxel
  • warfarin, a blood thinner
  • certain statins, including simvastatin

Taking it with certain antidepressants or other drugs that affect serotonin may cause serious serotonin-related side effects. Large doses by mouth, or use on the skin, might cause severe skin reactions in the sun; other side effects include diarrhea, dizziness, trouble sleeping, restlessness and skin tingling. It may be unsafe in pregnancy because it may raise the risk of birth defects, and breastfed babies of mothers taking it can have colic, drowsiness and lethargy (NCCIH).

St. John's Wort half-life and time to peak

  • Half-lifeNot listed
  • Time to peak (Tmax)Not listed

We could not find a single published half-life or time to peak for St. John's wort that applies to a supplement dose, so we do not list one. Herbal products are mixtures of many plant compounds, so no single figure would describe them.

How to track St. John's Wort in Dose Track

  1. Add St. John's Wort as a custom compound. Start typing its name and Dose Track fills in the details from its research library for you to check, and it sits next to everything else you take.
  2. Log each dose when you take it so your history shows exactly what you took and when.
  3. Set reminders on your own schedule, whether that is daily, weekly or every few days.
  4. Your log is stored on your phone and no account is needed. Data only leaves it for features you choose, like AI answers and lab reading.

How Dose Track handles peptides · Reconstitution calculator · Half-life calculator

5-HTP (5-Hydroxytryptophan)5-hydroxytryptophan, oxitriptan SAMe (S-Adenosyl-L-Methionine)S-adenosylmethionine, S-adenosyl-L-methionine Rhodiola roseaRhodiola rosea, golden root SaffronCrocus sativus, saffron extract

Frequently asked questions

What is the half-life of St. John's Wort?+
We could not find a single published half-life or time to peak for St. John's wort that applies to a supplement dose, so we do not list one. Herbal products are mixtures of many plant compounds, so no single figure would describe them.
What medicines interact with St. John's wort?+
Many. NCCIH lists birth control pills, warfarin, cyclosporine, digoxin and ivabradine, some antidepressants (amitriptyline, bupropion), seizure drugs (phenytoin, carbamazepine), HIV drugs (indinavir, nevirapine), cancer drugs (irinotecan, imatinib, docetaxel) and statins such as simvastatin. It can also cause serotonin-related side effects with some antidepressants. Tell every prescriber if you take it.
Does St. John's wort make birth control less effective?+
Yes. NCCIH lists birth control pills among the medicines St. John's wort can weaken. Talk to your prescriber about this before using it.
Can I track St. John's Wort in Dose Track?+
Yes. St. John's Wort is in Dose Track's research library, so when you add it as a custom compound its details are filled in for you to check. You can then log each dose next to your other compounds, set reminders on your own schedule, and see your history next to your lab results. Your log is stored on your phone and no account is needed. Data only leaves it for features you choose, like AI answers and lab reading.

Sources

  1. NIH National Center for Complementary and Integrative Health. St. John's wort (updated May 2025).
  2. FDA. Questions and answers on dietary supplements.

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