The short answer
Licorice-containing Gan cao can affect blood pressure, potassium and fluid balance. Review the exact preparation with your lithium prescriber; a predictable lithium-level change or protective spacing interval has not been established.
What this answer covers
Radix et Rhizoma Glycyrrhizae (Gan cao) oral preparations. Inspected EMA evidence concerns glycyrrhizin-containing roots and stolons of G. glabra, G. inflata and G. uralensis; exact processing and composition must be verified. Deglycyrrhizinated licorice is not assumed equivalent.
- Supplement or preparation
- Radix et Rhizoma Glycyrrhizae
- Medication ingredient
- lithium carbonate
The established concern is licorice’s own effects
Glycyrrhizin-containing licorice can cause sodium and water retention, potassium loss and raised blood pressure. In a small study of healthy adults, two weeks of licorice intake raised home systolic pressure and changed related hormones. That study did not include lithium users.
Do not predict a lithium level from this alone
Lithium treatment is sensitive to kidney function and changes in salt and fluid balance. Licorice’s effects therefore deserve review, but they do not establish that your lithium level will rise or fall. Licorice should not be used to correct a lithium level or a sodium problem.
Check the actual Gan cao preparation
The regulatory assessment covers specified licorice species, roots and stolons, and defined preparations. A processed Gan cao product or a product with glycyrrhizin removed may differ. Give your clinician the complete ingredient list and dose, especially if you have hypertension, kidney disease, low potassium or take a diuretic.
Ask about use, rather than relying on spacing
No lithium-specific interval has been shown to prevent licorice’s systemic effects. Discuss whether to use the product and whether blood pressure or electrolytes need checking. Report new swelling, weakness or palpitations promptly; lithium toxicity symptoms also require prompt medical assessment.
Evidence and practical considerations
Side effects & toxicity
Glycyrrhizin-containing licorice can change blood pressure, potassium and fluid balance, creating a reason for clinical review during lithium treatment without establishing a predictable lithium-level change.
- Exact scope
- Radix et Rhizoma Glycyrrhizae (Gan cao) oral preparations. Inspected EMA evidence concerns glycyrrhizin-containing roots and stolons of G. glabra, G. inflata and G. uralensis; exact processing and composition must be verified. Deglycyrrhizinated licorice is not assumed equivalent. 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
- No direct exact Gan cao-lithium study identified. Root/stolon assessment and a food-licorice trial do not establish every rhizome or processed preparation, lithium concentration direction, a safe dose or effective spacing.
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: Final regulatory herbal assessment
ema.europa.eu · Source check Sep 10, 2026
Population: Users of specified glycyrrhizin-containing licorice root preparations.
Describes sodium and water retention, potassium loss, hypertension and edema. Advises against use in specified renal, cardiovascular and electrolyte disorders and with medicines aggravating electrolyte imbalance.
How this applies: Relevant constituent and preparation concern for Radix et Rhizoma Glycyrrhizae, with root/stolon and species boundaries; not evidence for a spacing interval.
No direct lithium interaction or predictable direction of lithium concentration change established. Deglycyrrhizinated products and arbitrary processed Gan cao preparations are not equivalent.
Source 3: Original clinical research
ebi.ac.uk · Source check Sep 10, 2026
Population: 28 healthy young adults in a randomized, nonblinded crossover study.
Home systolic blood pressure increased and renin and aldosterone were suppressed.
How this applies: Indirect constituent-related physiology, not exact Gan cao-lithium pharmacokinetics.
No lithium exposure; abstract does not establish exact botanical species or equivalence to a root/rhizome supplement. Small, short study.
Source 4: 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: 0682b19a6243be60
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.