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Many people take licorice root supplements for digestion, sore throats, or stress relief, unaware they’re quietly undoing their blood pressure medication. If you’re on lisinopril, amlodipine, losartan, or any other antihypertensive drug, consuming even small amounts of real licorice root can cause your blood pressure to spike - sometimes dangerously so. This isn’t a rare side effect. It’s a well-documented, clinically significant interaction that’s sent people to the ER and forced doctors to rewrite treatment plans.
What’s Actually in Licorice Root?
Licorice root comes from the plant Glycyrrhiza glabra, and its sweetness isn’t just for flavor - it’s a chemical alarm bell. The main active compound is glycyrrhizin, which is about 50 times sweeter than sugar. But unlike artificial sweeteners, glycyrrhizin acts like a hormone in your body. It mimics aldosterone, a natural steroid that tells your kidneys to hold onto sodium and water while flushing out potassium. That sounds harmless until you realize: that’s exactly what high blood pressure drugs are trying to stop.
Raw licorice root can contain anywhere from 2% to 24% glycyrrhizin, depending on where it’s grown and how it’s processed. Commercial supplements often standardize this to 4-20%. That means a single teaspoon of licorice powder or a few pieces of real licorice candy could deliver more than 100 mg of glycyrrhizin - the threshold where effects start to show up in blood pressure readings.
How It Sabotages Your Blood Pressure Meds
Here’s the core problem: glycyrrhizin blocks an enzyme called 11β-hydroxysteroid dehydrogenase type 2. Normally, this enzyme protects your kidneys from being overstimulated by cortisol, a stress hormone that acts like aldosterone. When the enzyme is blocked, cortisol floods the mineralocorticoid receptors - and your body starts behaving as if it’s flooded with salt and water.
The result? Your blood volume goes up by 5-15%. Your potassium drops by 0.5-1.5 mmol/L. And your systolic blood pressure can climb 10-30 mmHg - even if you’re already on medication.
This doesn’t just make your meds less effective - it can nullify them entirely:
- ACE inhibitors (like lisinopril): Effectiveness drops by 30-50%. A 68-year-old man in the U.S. saw his BP jump from 130/80 to 185/105 after drinking licorice tea daily while on lisinopril.
- ARBs (like losartan): Around 25% loss in control. Patients report unexplained spikes even when adhering to their dose.
- Calcium channel blockers (like amlodipine): 15-20% reduction in effect. One Reddit user’s systolic pressure rose 22 points over two weeks after eating licorice candy.
- Potassium-sparing diuretics (like spironolactone): This is the worst combo. Licorice can completely cancel out the drug’s effect in 7-10 days, leading to dangerous fluid retention and low potassium.
It’s Not Just Supplements - It’s in Your Candy, Tea, and Cough Syrup
Most people think they’re safe if they’re not taking pills labeled “licorice root.” But that’s not true. Real licorice root is hiding in plain sight.
In the U.S., about 95% of black licorice candy uses anise oil instead of actual licorice. But the other 5%? That’s the danger zone. If the ingredient list says “licorice extract,” “Glycyrrhiza glabra,” or “licorice root,” you’re getting glycyrrhizin - even if the package looks like a candy bar.
It’s also in:
- Herbal teas marketed for digestion or detox
- Traditional Chinese medicine formulas (25% contain licorice root)
- Some cough syrups and throat lozenges
- Even certain tobacco products
A 2018 survey found that 30% of herbal laxatives contain licorice root. And in a 2019 case series, 6 out of 8 patients didn’t realize they were consuming real licorice - they thought they were just eating “flavored” snacks or drinking “herbal tea.”
What the Experts Say
Dr. Johanna Salge Blake, a nutrition professor at Boston University, puts it bluntly: “Consuming licorice and blood pressure meds together can lead to dangerously uncontrolled hypertension requiring emergency intervention.”
The Merck Manual (2023 edition) lists this interaction as a known clinical risk, citing 15 studies where patients needed hospitalization. Dr. Masato Tsuchiya from Kyoto University explains that enzyme inhibition kicks in at just 50 mg of glycyrrhizin per day - about the amount in 50 grams of real licorice candy. That’s less than two standard packs.
And here’s the kicker: the problem isn’t always obvious. Blood pressure rises slowly. Potassium drops silently. People feel fine - until they don’t. That’s why the New Zealand Centre for Adverse Reactions Monitoring recorded a case in 2019 of a 55-year-old man whose blood pressure spiked to 210/115 after starting licorice tea. He had no symptoms until he collapsed.
What You Should Do
If you’re on blood pressure medication, here’s what to do - no exceptions:
- Check every label. Look for “Glycyrrhiza glabra,” “licorice root,” or “licorice extract.” Avoid anything with those. Anise, fennel, or “natural flavor” are safe alternatives.
- Ask your pharmacist. They can scan your supplements, teas, and even over-the-counter cough syrups. Many don’t realize licorice is in them.
- Switch to DGL if you need licorice benefits. Deglycyrrhizinated licorice (DGL) has less than 1% glycyrrhizin and is safe for blood pressure. It’s commonly used for stomach ulcers and heartburn.
- Get your potassium checked. If you’ve consumed licorice in the last 30 days, ask for a serum potassium test. Levels below 3.0 mmol/L are dangerous and need immediate attention.
The American Heart Association recommends complete avoidance of glycyrrhizin for anyone on antihypertensives. The European Food Safety Authority says 100 mg/day is safe for healthy people - but if you’re on blood pressure meds, “safe” doesn’t apply.
What’s Changing?
Regulations are slowly catching up. The EU requires warning labels on products with more than 10 mg of glycyrrhizin per serving. The U.S. FDA has issued warnings but hasn’t mandated labeling. That’s changing. The proposed Dietary Supplement Listing Act of 2023 would force manufacturers to list active compound levels - including glycyrrhizin - on every supplement label.
For now, the burden is on you. Don’t assume a product is safe because it’s labeled “natural” or “herbal.” Don’t trust vague terms like “licorice flavor.” Read the fine print. If you’re unsure, leave it out.
Bottom Line
Licorice root isn’t just a sweet treat or a gentle herb. It’s a potent biochemical disruptor that can turn your carefully managed blood pressure into a ticking time bomb. You don’t need to avoid all herbal supplements - just this one. And if you’ve been eating licorice candy or drinking licorice tea while on meds, stop now. Talk to your doctor. Get your numbers checked. Your blood pressure is too important to risk for a sweet taste.
Written by Martha Elena
I'm a pharmaceutical research writer focused on drug safety and pharmacology. I support formulary and pharmacovigilance teams with literature reviews and real‑world evidence analyses. In my off-hours, I write evidence-based articles on medication use, disease management, and dietary supplements. My goal is to turn complex research into clear, practical insights for everyday readers.
All posts: Martha Elena