The short answer
St. John’s wort can increase serotonin-syndrome risk with lithium carbonate. Consult your prescriber before combining them; taking them hours apart is not an established safeguard.
What this answer covers
Oral Hypericum perforatum, commonly called St. John’s wort, with oral lithium carbonate. The label names the herb but does not establish a safe extract, constituent threshold or risk estimate for each preparation.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- lithium carbonate
The label names this combination
The lithium carbonate prescribing information specifically lists St. John’s wort among substances that can increase serotonin-syndrome risk. This is a potentially serious reaction involving excessive serotonin activity. The warning concerns combined effects in the body, rather than a demonstrated change in lithium absorption.
Ask before starting the herb
Discuss St. John’s wort with the prescriber before starting it for mood symptoms or another reason. If you already take both, contact the prescriber promptly to review the combination and all other medicines. The label does not identify a safe extract strength or a proven hours-apart schedule.
Recognize a cluster of symptoms
Agitation or confusion together with fever, sweating, a fast heartbeat, tremor, muscle stiffness, poor coordination or diarrhea may indicate serotonin syndrome. Seek urgent medical assessment if these symptoms develop, especially after adding or increasing a serotonergic product. Severe symptoms require emergency care.
Keep the whole treatment list visible
Other serotonergic medicines can add to the concern, so include antidepressants, pain medicines and supplements when you speak with the pharmacist. Product variability does not allow a reliable calculation of your risk. A clinician should decide whether the combination is appropriate and what monitoring or treatment changes are needed.
Evidence and practical considerations
Side effects & toxicity
Lithium carbonate labeling warns that St. John’s wort can increase the risk of serotonin syndrome when used together.
- Exact scope
- Oral Hypericum perforatum, commonly called St. John’s wort, with oral lithium carbonate. The label names the herb but does not establish a safe extract, constituent threshold or risk estimate for each preparation. with Exact lithium carbonate RxCUI 42351; the current NLM properties response classifies it as IN. Lithium-ion renal and pharmacodynamic effects are distinguished from salt-specific absorption and release kinetics. Other lithium salts are not automatically formulation-equivalent.
- Medication form and route
- Oral
What remains uncertain
- Regulatory warning names the herb; it does not quantify product-specific risk or demonstrate that a lower-strength extract or spacing eliminates it.
Factors that may matter: Exact product and preparation; Kidney function; Sodium and fluid balance; Other medicines; Changes in habitual intake.
Read the supporting source summaries
Source 1: Current U.S. prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral lithium carbonate.
Warns about sodium and fluid changes and lithium toxicity. Names St. John’s wort in its serotonin-syndrome warning. Xanthine preparations and alkalinizing agents can lower lithium concentrations through increased urinary excretion; monitoring and clinician-guided adjustment are advised.
How this applies: Exact medication prescribing information. Exact lithium carbonate RxCUI 42351; the current NLM properties response classifies it as IN. Lithium-ion renal and pharmacodynamic effects are distinguished from salt-specific absorption and release kinetics. Other lithium salts are not automatically formulation-equivalent.
Class warnings do not establish a measured effect for every botanical or citrate preparation. Does not establish a universal hours-apart solution or fixed dose change.
Source 2: Authoritative medication terminology
rxnav.nlm.nih.gov · Source check Sep 10, 2026
Population: Medication terminology, not clinical participants.
Current response identifies lithium carbonate with term type IN.
How this applies: Exact identifier and current term type; no corpus identity mutation.
Terminology does not establish clinical equivalence with lithium citrate or other salts and does not prove an interaction.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Sources checked and article drafted. | |
| Research summary published |
Article revision: 27143894314ffa56
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.