Merck Manual

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Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Reviewed/Revised Jan 2022 | Modified Sep 2022

What is licorice?

Natural licorice, which has a very sweet taste, is extracted from the root of a shrub and used medicinally as a capsule, tablet, liquid extract, or topical gel. Most licorice candy made in the United States is artificially flavored and does not contain natural licorice. Glycyrrhizin is the active ingredient in natural licorice. For people who are particularly sensitive to the effects of glycyrrhizin, licorice products that are specially treated to contain a much lower amount of glycyrrhizin (about one tenth of the usual amount) are available. These products are called deglycyrrhizinated licorice.

What claims are made about licorice?

Does licorice work?

There is not enough evidence to determine whether licorice is effective for stomach ulcers or complications caused by hepatitis C or other liver diseases. Evidence does indicate that licorice in combination with other herbs relieves symptoms of indigestion and irritable bowel syndrome Irritable Bowel Syndrome (IBS) Irritable bowel syndrome is a disorder of the digestive tract that causes recurring abdominal pain and constipation or diarrhea. Symptoms vary but often include lower abdominal pain, bloating... read more ; however, clinical trials of both licorice alone and in combination are limited, and further evaluation is required.

What are the possible side effects of licorice?

When licorice is consumed normally or at lower doses, there are few side effects. However, at high doses, glycyrrhizin causes the kidneys to retain salt and water, possibly leading to high blood pressure. It also causes the kidneys to excrete potassium, possibly causing low potassium levels in the blood. Increased potassium excretion can be a particular problem for people who have heart disease and for those who take digoxin or diuretics that increase potassium excretion in urine. Such people and those who have high blood pressure should avoid taking licorice.

Licorice may increase the risk of premature delivery. Thus, pregnant women should not take licorice.

What drug interactions occur with licorice?

As mentioned above, increased potassium secretion can be a particular problem for people who take digoxin or diuretics that increase potassium excretion in urine. Such people should not take licorice, because low potassium may lead to cardiac arrhythmias (altered heartbeat rhythms) and/or muscle weakness. Licorice may decrease effectiveness of antihypertensive (blood pressure–lowering) drugs due to an increase in salt and water retention.

Also, some experts believe that licorice has some activity similar to a type of antidepressant called monoamine oxidase (MAO) inhibitors and thus may intensify side effects of these drugs.

Licorice may interact with warfarin and make it less effective, increasing the risk of blood clots.


Consumed in moderation, licorice may have acceptable safety at normal doses and may help relieve indigestion and irritable bowel syndrome. However, pregnant women, people taking warfarin, and possibly people taking digoxin or certain diuretics should not take licorice.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Digitek , Lanoxicaps, Lanoxin, Lanoxin Pediatric
Coumadin, Jantoven
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