Licorice root

What it is

Licorice is the root and rhizome of Glycyrrhiza glabra, a perennial herb grown across Europe, Asia and the Middle East. It is used as a medicinal herb and as a flavouring in candy, foods and tobacco. Its main active component, glycyrrhizin (glycyrrhizic acid), is what causes most of its side effects. Many US 'licorice' sweets contain anise oil instead of real licorice.

What the research says

The best evidence concerns harm. A meta-analysis of 18 studies found that regular glycyrrhizin intake of 100 mg a day or more raises blood pressure and lowers potassium. A 2024 randomized trial saw a rise in blood pressure at just 100 mg glycyrrhizic acid a day. Case reports describe dangerous heart rhythms. For benefits, a meta-analysis found that licorice applied to the throat before intubation reduced post-operative sore throat. However, a trial of licorice gargle after throat surgery found no pain benefit. One small industry trial reported relief of indigestion with a low-glycyrrhizin extract.

Evidence grade: Limited evidence.

What goes wrong

A meta-analysis of 18 studies found that regular intake of at least 100 mg/day glycyrrhizic acid raised blood pressure and lowered plasma potassium, renin and aldosterone. (Source 1)

• Meta-analysis, Moderate certainty.
• Size: 337 participants in 18 studies.
• Who: Mostly healthy volunteers.
• How long: Chronic ingestion (varied)
• Result: SBP +5.45 mm Hg (95% CI 3.51-7.39); DBP +3.19 mm Hg (95% CI 0.10-6.29); potassium, renin activity and aldosterone significantly decreased.
• Funding: not stated.

A total of 18 studies (n=337) were included in the meta-analysis. There was a statistically significant increase in mean systolic blood pressure (5.45 mm Hg, 95% CI 3.51–7.39) and diastolic blood pressure (3.19 mm Hg, 95% CI 0.10–6.29) after chronic ingestion of a product containing glycyrrhizic acid.

A randomized crossover trial in 28 healthy volunteers found that licorice with only 100 mg glycyrrhizic acid a day for 2 weeks raised home blood pressure and suppressed renin and aldosterone. (Source 2)

• Randomized trial, Moderate certainty.
• Size: 28 healthy volunteers.
• Who: Healthy young adults.
• How long: 2 weeks per period.
• Result: Systolic home BP about 3.1 mm Hg higher than control (as reported); renin and aldosterone suppressed.
• Funding: independent (Linköping University and Swedish research foundations); registered NCT05661721.

We found licorice to be more potent than previously known, with significant increases in BP, after a daily intake of only 100 mg GA.

Case report: an 89-year-old woman taking herbal medicines high in licorice had severe low potassium, rhabdomyolysis, pulseless ventricular tachycardia needing defibrillation, and then heart failure. (Source 3)

• Case report, Very low certainty.
• Size: 1 patient.
• Who: 89-year-old woman.
• How long: Not stated.
• Result: Severe hypokalaemia with metabolic alkalosis; renin and aldosterone highly suppressed.
• Funding: not stated.

The electrocardiogram in the emergency department revealed pulseless ventricular tachycardia, thus, emergent defibrillation was delivered.

Case report: a 78-year-old man presented with low potassium that would not correct and new high blood pressure from licorice toxicity. (Source 4)

• Case report, Very low certainty.
• Size: 1 patient.
• Who: 78-year-old man.
• How long: Not stated.
• Result: Triad of severe hypokalaemia, metabolic alkalosis and hypertension.
• Funding: not stated.

We present the intriguing case of a 78-year-old male who was referred for evaluation of refractory hypokalemia and newly developed hypertension.

NCCIH (position, April 2025) states that glycyrrhizin can cause irregular heartbeat and cardiac arrest, notes reported interactions with corticosteroids, and calls large intake in pregnancy unsafe. (Source 5)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: Not applicable.
• How long: Not applicable.
• Result: Not applicable.
• Funding: government (NIH)

Interactions between licorice and corticosteroids have been reported.

The EU Scientific Committee on Food (position, 10 April 2003) set 100 mg/day glycyrrhizic acid as an upper limit for regular intake. It said this may not protect people with high blood pressure, slow gut transit or reduced 11-beta-HSD2 activity. (Source 6)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: General population.
• How long: Not applicable.
• Result: Upper limit 100 mg/day; no ADI could be derived.
• Funding: EU advisory committee.

At the same time, the Committee realises that within the human population there are subgroups for which this upper limit might not offer sufficient protection.

What the evidence supports

A meta-analysis of 5 RCTs found that licorice applied to the throat before intubation reduced the incidence and severity of post-operative sore throat, with no significant adverse events. (Source 7)

• Meta-analysis, Moderate certainty.
• Size: 609 patients in 5 RCTs.
• Who: Adults intubated for elective surgery.
• How long: Peri-operative.
• Result: Incidence RR 0.44 (95% CI 0.28-0.69); severity SMD -0.69 (95% CI -0.96 to -0.43)
• Funding: not stated.

Compared with non-analgesic control, topical licorice was associated with a reduced incidence (risk ratio, 0.44; 95% confidence interval (CI), 0.28–0.69; P < 0.001) and severity (standardized mean difference, −0.69; 95% CI, −0.96, −0.43; P < 0.001) of postoperative sore throat.

A small placebo-controlled RCT found that a Glycyrrhiza glabra extract (GutGard, 75 mg twice daily) reduced functional dyspepsia symptoms over 30 days. It was a single small trial of a branded product. (Source 8)

• Randomized trial, Low certainty.
• Size: 50 patients.
• Who: Adults with functional dyspepsia.
• How long: 30 days.
• Result: Significant decrease in total symptom scores at day 15 and 30 vs placebo; no treatment-related adverse effects.
• Funding: likely industry-linked (branded product; funding not captured)

GutGard was generally found to be safe and well-tolerated by all patients. GutGard has shown significant efficacy in the management of functional dyspepsia.

What the evidence does not support

A double-blind RCT found that gargling 1 g licorice did not reduce pain or morphine use after throat (oropharyngeal) surgery. (Source 9)

• Randomized trial, Moderate certainty.
• Size: 126 patients (65 licorice, 61 placebo)
• Who: Adults having elective oropharyngeal surgery.
• How long: Up to 3 days after surgery.
• Result: Pain mean difference -0.09 (95.2% CI -0.88 to 0.70): non-inferior but not better.
• Funding: departmental funding (independent)

Gargling with licorice did not significantly or meaningfully reduce postoperative pain or morphine consumption in patients recovering from oropharyngeal surgery.

A phase 1 study found that one specific licorice extract, depleted of glycyrrhizic acid (less than 1%), taken for 2 weeks, did not cause clinically relevant interactions via CYP3A4/5, CYP2C9, CYP2D6 or CYP1A2. This applies only to that extract, not to licorice products generally, and does not address glycyrrhizin-driven interactions such as potassium loss with diuretics. (Source 10)

• Blood level study, Low certainty.
• Size: 14 participants.
• Who: Healthy menopausal and postmenopausal women.
• How long: 2 weeks.
• Result: No significant change in probe-drug AUCs.
• Funding: not stated.

Limit of this finding: The extract tested had less than 1% glycyrrhizic acid. The 'no clinically relevant interactions' conclusion applies only to that low-glycyrrhizin extract; it should not be read as showing that ordinary licorice or other licorice supplements are free of drug interactions.

According to the US Food and Drug Administration guidance, which is based on changes in the AUC of each probe substrate drug, the investigated licorice extract should not cause any clinically relevant pharmacokinetic interactions with respect to CYP3A4/5, CYP2C9, CYP2D6, or CYP1A2.

Where the research disagrees

Whether 100 mg/day glycyrrhizic acid is a safe upper limit

• EU Scientific Committee on Food (2003), review of toxicology and small volunteer studies: The Committee considers that this upper limit for regular ingestion of 100 mg/day provides a sufficient level of protection for the majority of the population. (Source 6)
• Randomized crossover trial authors (2024), randomized crossover trial, 28 healthy volunteers: We found licorice to be more potent than previously known, with significant increases in BP, after a daily intake of only 100 mg GA. (Source 2)

How much

• Reference intake: No RDA or AI exists: licorice is not an essential nutrient. (Source 6)
• Upper limit: EU Scientific Committee on Food (2003): upper limit for regular ingestion of 100 mg/day glycyrrhizic acid from all sources; no ADI could be derived. The 2024 AJCN trial found blood pressure rose at this dose. (Source 6)
• Studied: Blood-pressure trial: licorice providing 100 mg glycyrrhizic acid per day for 2 weeks. (Source 2)
• Studied: Dyspepsia trial: GutGard extract 75 mg twice daily for 30 days. (Source 8)
• Studied: Surgery trial: 1 g licorice gargle before and up to 3 days after surgery. (Source 9)

A common belief, and what the research shows

The belief: Licorice is just a harmless candy flavour.

What the research shows: Real licorice contains glycyrrhizin, which raises blood pressure and lowers potassium. The meta-analysis found this happens 'even at modest doses', and NCCIH notes it can cause 'irregular heartbeat and cardiac arrest'. Many US sweets, however, are flavoured with anise oil and contain no licorice.

Questions and answers

What is it?

Licorice is the sweet root of the Glycyrrhiza glabra plant. It is used as a herbal medicine and as a flavouring in sweets and other foods. Its main active compound is glycyrrhizin, also called glycyrrhizic acid. (Source 10)

What does it do in the body?

Glycyrrhizin blocks an enzyme in the kidney, 11-beta-HSD2. This lets the body's own cortisol act like the hormone aldosterone, so the kidneys hold on to salt and lose potassium, and blood pressure goes up. (Source 3)

Is it good or bad for you?

It depends on dose and person. Regular glycyrrhizin intake raises blood pressure and lowers potassium, and in extreme cases has led to dangerous heart rhythms. Applied to the throat, it has reduced sore throat after anaesthesia. People with heart disease or high blood pressure, and pregnant women, are at most risk. (Source 1)

How do you get more of it?

People take in glycyrrhizin from licorice sweets, licorice-flavoured products, teas and herbal supplements. The EU upper limit counts all of these sources together. This describes exposure, not a recommendation. (Source 6)

If it is harmful, what reduces it?

Glycyrrhizin intake falls when people eat less real licorice or switch to deglycyrrhizinated licorice (DGL), which has the glycyrrhizin removed. NCCIH says DGL products might be safe for up to 4 months. (Source 5)

Why might someone be low in it or missing it?

Does not apply. Licorice is not a nutrient, so no one is deficient in it. (Source 6)

We searched: SCF 2003 opinion, NCCIH, meta-analysis; no deficiency concept

Which whole foods contain it or feed it?

Real licorice is in some licorice candy, other foods, teas and tobacco products. Many US 'licorice' sweets contain anise oil and no real licorice at all. (Source 5)

What happens if you do not have it?

Nothing is known to happen. Licorice is not essential to the body. (Source 5)

We searched: SCF 2003, NCCIH

How can you test for it?

There is no routine test for licorice itself. Its effects show up on standard blood tests: low potassium, metabolic alkalosis, and suppressed renin and aldosterone. These patterns point doctors to licorice once other causes are ruled out. (Source 3)

References

1. Journal of Human Hypertension. The association between consistent licorice ingestion, hypertension and hypokalaemia: a systematic review and meta-analysis. 2017. DOI 10.1038/jhh.2017.45. Read the source
2. American Journal of Clinical Nutrition. A low dose of daily licorice intake affects renin, aldosterone, and home blood pressure in a randomized crossover trial. 2024. PMID 38246526. Read the source
3. European Heart Journal - Case Reports. Dramatic recovery of left ventricular dysfunction in a patient with pseudoaldosteronism, hypokalaemia, and rhabdomyolysis: a case report. 2023. DOI 10.1093/ehjcr/ytad398. Read the source
4. Cureus. Licorice Toxicity Presenting As Refractory Hypokalemia and Hypertension in an Elderly Patient. 2024. PMID 39498427, DOI 10.7759/cureus.72975. Read the source
5. National Center for Complementary and Integrative Health (NIH). Licorice Root. 2025. Read the source
6. European Commission Scientific Committee on Food. Opinion of the Scientific Committee on Food on glycyrrhizinic acid and its ammonium salt. 2003. Read the source
7. Journal of Clinical Anesthesia. Topical application of licorice for prevention of postoperative sore throat in adults: A systematic review and meta-analysis. 2019. PMID 30391446. Read the source
8. Evidence-Based Complementary and Alternative Medicine. An Extract of Glycyrrhiza glabra (GutGard) Alleviates Symptoms of Functional Dyspepsia: A Randomized, Double-Blind, Placebo-Controlled Study. 2012. PMID 21747893, DOI 10.1155/2012/216970. Read the source
9. Journal of Personalized Medicine (MDPI). Pain after Licorice or Sugar-Water Gargling in Patients Recovering from Oropharyngeal Surgery—A Randomized, Double-Blind Trial. 2024. DOI 10.3390/jpm14101056. Read the source
10. Drug Metabolism and Disposition 51(2):199-204. Pharmacokinetic Interactions of a Licorice Dietary Supplement with Cytochrome P450 Enzymes in Female Participants. 2023. DOI 10.1124/dmd.122.001050. Read the source