The short answer
Licorice containing glycyrrhizin can raise blood pressure and work against blood-pressure treatment. Avoid starting it without prescriber advice while taking doxazosin; a dose gap has not been shown to prevent this effect.
What this answer covers
Oral doxazosin with glycyrrhizin-containing Glycyrrhiza glabra root or stolon products. Deglycyrrhizinated licorice and other plant parts are not assumed equivalent.
- Supplement or preparation
- Glycyrrhiza glabra
- Medication ingredient
- doxazosin
Why licorice is a concern
The current European assessment states that licorice can raise blood pressure and counteract antihypertensive medicines. It can also cause fluid retention and potassium loss. This is a concern about the body’s response to licorice, not proof that it blocks absorption of doxazosin.
What a human trial adds
A randomized study in 28 healthy adults found increased home systolic pressure and suppressed renin and aldosterone after two weeks of licorice supplying 100 mg daily of glycyrrhizic acid. It did not test doxazosin or establish a universally safe amount.
Identify the exact licorice product
Check root extracts, teas and combination products for licorice and glycyrrhizin. Deglycyrrhizinated licorice has a different constituent profile, and an unspecified botanical label cannot establish equivalence. Have the pharmacist review the product before use rather than choosing a timing gap.
When to contact your care team
Report a rise in your usual BP readings, new swelling, weakness or palpitations promptly. Your clinician may assess electrolytes and reconsider the licorice exposure. Do not increase doxazosin or add potassium on your own to compensate for an unreviewed supplement.
Evidence and practical considerations
Side effects & toxicity
Glycyrrhizin-containing licorice can oppose antihypertensive treatment through BP and electrolyte effects, without proving reduced doxazosin absorption.
- Exact scope
- Oral doxazosin with glycyrrhizin-containing Glycyrrhiza glabra root or stolon products. Deglycyrrhizinated licorice and other plant parts are not assumed equivalent. with Current RxNorm confirms doxazosin RxCUI 49276 IN. Immediate-release mesylate tablets provide equivalent doxazosin free base 1, 2, 4 or 8 mg. No automatic extended-release transfer.
- Medication form and route
- Oral
What remains uncertain
- Regulatory class-level PD precaution plus supplement trial; no measured exact-pair PK, absorption decline, universal threshold or validated spacing.
Factors that may matter: Exact preparation and dose; Blood pressure and symptoms; Treatment initiation or dose change; Other medicines.
Read the supporting source summaries
Source 1: Current prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed doxazosin mesylate tablets.
Postural hypotension and syncope, particularly after initial dose or dose escalation.
How this applies: Exact ingredient through the stated labeled salt and oral formulation. Current RxNorm confirms doxazosin RxCUI 49276 IN. Immediate-release mesylate tablets provide equivalent doxazosin free base 1, 2, 4 or 8 mg. No automatic extended-release transfer.
BPH treatment does not remove BP effects; no generic herb-specific outcome evidence.
Source 2: Final regulatory assessment
ema.europa.eu · Source check Sep 10, 2026
Population: Users of defined licorice root and stolon preparations.
Mineralocorticoid effects can cause potassium loss, fluid retention and hypertension. Explicitly states licorice may counteract antihypertensive action.
How this applies: Conditional pharmacodynamic bridge from glycyrrhizin-containing G.glabra root to BP-lowering medication.
Not a measured doxazosin absorption or concentration study; deglycyrrhizinated products and unspecified plant parts differ.
Source 3: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 28 healthy young adults in a randomized crossover.
Home systolic BP rose and renin/aldosterone were suppressed.
How this applies: Exact preparation and endpoint boundaries retained; this is not a measured doxazosin combination unless explicitly stated.
Abstract-only; no doxazosin co-use. Product amount does not establish a safe limit for every licorice preparation.
Source 4: Medication terminology
rxnav.nlm.nih.gov · Source check Sep 10, 2026
Population: Terminology.
doxazosin is IN.
How this applies: Exact ingredient.
Not clinical evidence.
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: 5f113b6df94ee2fc
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.