Category: Herbs & Ingredients
Most herb interactions are theoretical. This one is not. Licorice root reliably raises blood pressure and drives potassium down through a mechanism that is well understood and well documented, which makes it one of the few genuinely strong herb interactions with blood pressure medication. Here is how it works and why it matters.
Category: Herbs and Ingredients | Reading time: ~13 min | Level: Intermediate
If you have read enough of these interaction articles, you may have noticed a recurring honesty: most herb-drug warnings are built on thin ground, theory and animal studies and the occasional case report, and the responsible thing is to say so. Licorice root is the exception that makes the honesty credible. This is not a maybe. Licorice reliably raises blood pressure and drives potassium down, through a mechanism that has been understood for over half a century and reproduced in people again and again [1][2]. When a topic like this comes up, the job is not to hedge. It is to be as clear about a real risk as we are careful about the imaginary ones.
That clarity matters most for one group: anyone on blood pressure medication. Licorice does not merely coexist awkwardly with antihypertensives. It actively works in the opposite direction, pushing blood pressure up while your medication tries to bring it down, and it does so while depleting the potassium that several important medicines depend on you keeping. This is a strong interaction, and it deserves to be named as one.
Everything here is drawn from the published literature and regulatory reviews. It is not a claim generated by any single product or platform.
Licorice root comes from Glycyrrhiza glabra, and its defining compound is glycyrrhizin, the source of both its sweetness and its trouble. Licorice appears in far more than obvious licorice sweets: it turns up in some teas, throat and digestive products, and herbal supplements, which is part of why the interaction catches people out.
The one-sentence mechanism is this: glycyrrhizin is converted in the body into a substance that blocks a protective kidney enzyme, which lets your own cortisol act like the hormone aldosterone, telling the body to retain sodium and water and to shed potassium, so blood pressure climbs and potassium falls. That state is called pseudohyperaldosteronism, and it is the engine behind everything in this article. Because it acts on your own hormone system, it does not need a drug to be present to cause harm; a blood pressure medication simply adds an interaction on top of an already active effect.
The foundation here is old and solid. In 1968, Conn and colleagues described licorice-induced pseudoaldosteronism in detail: hypertension, low potassium, suppressed renin and the hormonal fingerprint that gave the condition its name [1]. That was not a one-off curiosity. It defined a recognised clinical entity that has been confirmed repeatedly since.
Modern evidence sharpens rather than softens the picture. A systematic review and meta-analysis by Penninkilampi and colleagues in 2017 pooled the human data on consistent licorice consumption and found it associated with higher blood pressure and lower potassium [2]. This is exactly the kind of evidence most herb interactions lack: not a single dramatic case, but a body of human data showing a consistent, quantifiable effect in the direction the mechanism predicts. Alongside it sit numerous published case reports of heavy or prolonged licorice intake precipitating hypertensive crises and severe potassium drops, some requiring hospital care.
The threshold is lower than people assume. European food safety advice sets a guidance upper limit of 100 milligrams of glycyrrhizin per day, a level reachable through modest but regular consumption of licorice products [3]. Sensitivity varies between individuals, and prolonged daily intake is riskier than an occasional taste, but there is no comfortable margin to lean on, particularly for someone already prone to high blood pressure.
The grade, stated plainly, is strong. A clear mechanism, decades of confirmation, a meta-analysis and human case reports all line up. This is as well established as herb interactions get.
The blood pressure effect is the headline, but the potassium drop is what turns licorice from a single-medicine concern into a multi-medicine one.
Low potassium is not just a number on a blood test. It can cause muscle weakness, cramps and fatigue, and at its worst it disturbs the heart's rhythm, which is where the danger lies. Licorice lowers potassium as part of its core mechanism, and two common medication scenarios make that worse.
The first is diuretics that also lower potassium, notably thiazide and loop diuretics used for blood pressure. Stack their potassium-lowering effect on licorice's, and the drop can become significant. The second is digoxin, a heart medicine whose safety is sensitive to potassium levels: when potassium falls, the risk of serious digoxin effects rises. So licorice can endanger someone through a heart medicine without touching that medicine directly, simply by depleting the potassium the drug depends on.
This is why the licorice interaction earns a stronger warning than the blood pressure story alone would justify. It is a blood pressure effect and a potassium effect at once, and the potassium effect reaches into diuretics and heart medicines that many people on antihypertensives also take.
There is an important piece of good news that people often miss, and getting it wrong in either direction causes needless confusion.
Deglycyrrhizinated licorice, usually labelled DGL, has had the glycyrrhizin removed, and glycyrrhizin is the entire cause of the blood pressure and potassium effects [4]. Take the compound out, and DGL does not carry the same risk. This is precisely why DGL is the form commonly used for digestive comfort: it keeps the traditional soothing use while avoiding the cardiovascular downside of whole licorice.
The practical consequence is that the label matters enormously. A product marked deglycyrrhizinated or DGL is a fundamentally different proposition from standard licorice root for anyone concerned about blood pressure. It is still worth mentioning any supplement to your prescriber, but the blood pressure and potassium mechanism is specific to the glycyrrhizin-containing form. Do not let a blanket fear of the word licorice obscure that distinction, and do not let the reassuring DGL research lull you into treating standard licorice as safe.
The mechanism is only half the danger. The other half is that people rarely realise how much licorice they are actually consuming, because glycyrrhizin travels under many names and in many products that do not announce themselves as licorice.
The obvious source is licorice confectionery, and here portion size matters more than people think: regular daily consumption of licorice sweets has repeatedly landed people in hospital with high blood pressure and dangerously low potassium. But the herb reaches far beyond the sweet aisle. It appears in some herbal teas, often blended with other botanicals so its presence is easy to miss. It is used in throat and digestive remedies for its soothing quality. It turns up in multi-herb supplements, sometimes as a minor listed ingredient that a buyer skims past. Certain flavourings and chewing products contain it too. Because the effect is cumulative and dose-related, a person taking a licorice tea, a licorice-containing supplement and the occasional sweet can quietly stack up more glycyrrhizin than any single source would suggest.
This is why the interaction so often surprises both patients and clinicians. Someone whose blood pressure has crept out of control, or whose potassium has fallen without obvious cause, may not connect it to a herbal tea they drink every evening, because they never thought of it as a drug. The investigation can run in circles until someone asks the specific question: are you consuming licorice in any form, including teas and supplements. Often the answer, once the net is cast wide enough, is yes.
The practical defence is a habit of reading labels for glycyrrhiza, licorice or liquorice, and of treating any regular licorice-containing product as part of your medication picture rather than as food. For anyone on blood pressure medication, that small act of label-reading is worth more than a vague sense that licorice is best avoided, because the trap is not the sweet you know about; it is the daily source you have stopped noticing.
The guidance here is firmer than in most interaction articles, because the evidence is firmer.
If you have high blood pressure or take blood pressure medication, treat standard licorice root as an ingredient to avoid unless a clinician specifically advises otherwise. It works against your treatment through an established mechanism, and the downside includes documented hypertensive crises.
Know where licorice hides. Check sweets, teas, throat and digestive products and herbal supplements, because the interaction commonly catches people who did not realise they were consuming it regularly.
If you take a potassium-lowering diuretic or a heart medicine such as digoxin, the potassium effect makes licorice a particular concern, and this belongs in a conversation with whoever manages those medicines.
Learn the warning signs, rising blood pressure and the symptoms of low potassium such as muscle weakness, cramps, fatigue and palpitations, and seek medical advice if they appear rather than waiting them out.
If you want the soothing traditional uses of licorice without the cardiovascular effect, deglycyrrhizinated licorice is the form designed to avoid it, though it too should be mentioned to your prescriber.
Pregnant, breastfeeding, or on medication? Check with a healthcare professional first.
Licorice is a useful illustration of what honest grading looks like: most herb interactions get a cautious, low-confidence flag, and this one gets a strong one, because the evidence demands it. Structure and function only, whole licorice is discussed for its traditional soothing uses, never as a treatment for any condition, and it is presented with the blood pressure and potassium mechanism stated plainly rather than softened, along with the DGL distinction that changes the picture.
If you are weighing licorice against your medication list, Remy, the PlantRx assistant, can surface the published mechanism and cautions with their honest grade, distinguish standard licorice from the deglycyrrhizinated form, and point you back to the prescriber conversation that a strong interaction like this one warrants.
1. Conn JW, Rovner DR, Cohen EL (1968). Licorice-induced pseudoaldosteronism: hypertension, hypokalemia, aldosteronopenia, and suppressed plasma renin activity. JAMA. PMID 5695305. Foundational description of the clinical syndrome. 2. Penninkilampi R, Eslick EM, Eslick GD (2017). The association between consistent licorice ingestion, hypertension and hypokalaemia: a systematic review and meta-analysis. Journal of Human Hypertension. PMID 28660884. Pooled human data showing consistent effects on blood pressure and potassium. 3. European Commission Scientific Committee on Food (SCF) (2003). Opinion on glycyrrhizinic acid and its ammonium salt. Regulatory opinion setting a guidance upper limit of 100 mg glycyrrhizin per day. 4. National Center for Complementary and Integrative Health (NCCIH). Licorice Root: Usefulness and Safety. Government evidence and safety review. nccih.nih.gov/health/licorice-root. Cited for the blood pressure caution and the deglycyrrhizinated licorice distinction.
This is one of the clearest do-not-combine-without-advice situations in herbal safety. Licorice root reliably raises blood pressure through a well-understood mechanism, so it works directly against blood pressure medication and can undermine your control. Case reports document dangerous blood pressure spikes from heavy or prolonged use. If you have high blood pressure or take antihypertensives, standard licorice root is one to avoid unless a clinician says otherwise. The deglycyrrhizinated form is a different matter.
Its active compound, glycyrrhizin, is converted in the body into a substance that blocks an enzyme normally protecting the kidney from cortisol. With that protection removed, cortisol acts like the hormone aldosterone, telling the body to hold on to sodium and water and to shed potassium. The result is rising blood pressure and falling potassium, a state doctors call pseudohyperaldosteronism. It is a real, reproducible physiological effect, not a vague caution.
DGL has had the glycyrrhizin removed, which is the very compound responsible for the blood pressure effect, so DGL does not carry the same risk. This distinction matters a great deal: DGL is often used for digestive comfort precisely because it avoids the blood pressure and potassium problems of whole licorice. Always check whether a product is standard licorice or DGL, and still mention any supplement to your prescriber.
Less than people expect, and it depends on the amount of glycyrrhizin. European food safety advice sets an upper limit of 100 milligrams of glycyrrhizin a day, which can be reached through modest but regular consumption of licorice sweets, teas or supplements. Sensitivity varies between people, and prolonged daily intake is riskier than an occasional taste, but the threshold for an effect is not high, especially for someone already prone to high blood pressure.
The signs track the mechanism: rising blood pressure, and symptoms of low potassium such as muscle weakness, cramps, fatigue and, in serious cases, heart rhythm disturbances. Headache and swelling can also feature. Because low potassium can be dangerous, particularly alongside certain heart and diuretic medicines, these are symptoms to take seriously and to seek medical advice about rather than wait out.
Yes, and these combinations sharpen the risk. Diuretics that lower potassium can add to licorice's potassium-lowering effect, deepening the drop. And low potassium raises the risk of serious effects with heart medicines such as digoxin. So licorice is not only a blood pressure concern; it is a potassium concern that ripples into several important medicines. This is why the interaction deserves the strong grade it gets.
Occasional small amounts are lower risk than daily heavy intake, and the effect is dose- and duration-related. The honest caveats are that sensitivity varies, that licorice hides in more products than people realise, from sweets to teas to some supplements, and that someone already on blood pressure medication has less margin. The safe habit is to know where licorice is in your diet and supplements, keep it modest, and tell your prescriber, rather than assume a little is always fine.
Because it has what most herb interactions lack: a clear, reproducible mechanism, human case reports of real harm, and a meta-analysis showing consistent effects on blood pressure and potassium. Many herb cautions rest on theory or animal data. Licorice rests on established physiology and documented clinical events. Honesty cuts both ways here: when we say most herb interactions are weak, we also have to say plainly that this one is not.
Yes. The blood pressure and potassium effects do not require you to be on any drug; they come from the herb acting on your own hormone system. Heavy or prolonged licorice intake has caused hypertensive crises and dangerous potassium drops in people who were not taking blood pressure medication at all. Being on medication changes the picture by adding an interaction on top, but licorice is worth respecting on its own terms.