Licorice and Blood Pressure Medication Interactions: What You Need to Know

If you're taking medication for high blood pressure, eating black licorice candy or drinking licorice tea might be more dangerous than you think. It's not just about sugar or taste-it's about a powerful chemical in licorice called glycyrrhizin that can undo the work of your meds and push your blood pressure higher instead of lower. This isn't a myth or a warning from an old wives' tale. It's backed by decades of clinical research and documented in major medical handbooks like the Merck Manual and MSD Manual. And if you're over 60, female, or already have heart problems, the risk is even higher.

How Licorice Actually Raises Blood Pressure

Glycyrrhizin isn't just a flavoring. When you consume it, your body breaks it down into glycyrrhetic acid, which blocks a key enzyme in your kidneys called 11β-HSD2. This enzyme normally protects your body from being overstimulated by cortisol, a stress hormone that acts like a weak version of aldosterone-the hormone that tells your kidneys to hold onto salt and water.

When 11β-HSD2 is blocked, cortisol takes over. Your kidneys start behaving as if they're flooded with aldosterone: they hang onto sodium, push out potassium, and retain extra fluid. That extra fluid means more volume in your blood vessels. More volume = higher blood pressure. This condition is called pseudoaldosteronism, and it mimics what happens in rare hormonal disorders-but here, it's caused by something you ate.

Studies show this isn't subtle. A meta-analysis of 26 clinical trials found that people who regularly consumed licorice saw their systolic blood pressure rise by an average of 5.45 mmHg and diastolic by 1.74-3.19 mmHg. That might not sound like much, but for someone on medication to keep their BP under 130/80, that’s enough to push them into the hypertensive range. And it’s not just a one-time spike-it builds up over time with daily use.

Why This Matters for Your Blood Pressure Pills

Most blood pressure medications work by reducing fluid volume, relaxing blood vessels, or blocking hormones that tighten arteries. Licorice does the exact opposite. That means it directly fights the effect of every major class of antihypertensive drugs:

• Diuretics like hydrochlorothiazide help you pee out extra fluid-but licorice makes your body hold onto even more, canceling out the benefit.
• ACE inhibitors like lisinopril or captopril lower BP by relaxing blood vessels and reducing fluid-but licorice floods your system with sodium and water, making them less effective.
• Calcium channel blockers like amlodipine or nifedipine widen arteries-but if your blood volume is too high, they can’t keep up.
• Potassium-sparing drugs like spironolactone are designed to keep potassium levels stable-but licorice drains potassium so fast that even these drugs can’t compensate.

Worse, when you combine licorice with potassium-wasting diuretics, you're not just fighting your meds-you're putting yourself at risk for dangerously low potassium (hypokalemia). Levels below 3.5 mmol/L can cause muscle weakness, cramps, fatigue, and abnormal heart rhythms. In extreme cases, it can trigger cardiac arrest.

The Dangerous Combo: Licorice and Digoxin

One of the most serious-and potentially deadly-interactions happens with digoxin, a heart medication used for atrial fibrillation and heart failure. Digoxin works by slowing the heart rate and strengthening contractions. But it’s extremely sensitive to potassium levels. When potassium drops, digoxin binds more tightly to heart cells, and suddenly, a safe dose becomes toxic.

A documented case in the journal Cardiology involved an older man who took a herbal laxative containing licorice root. Within weeks, he developed severe digoxin toxicity: nausea, irregular heartbeat, and congestive heart failure. His potassium level had dropped to 2.8 mmol/L. He didn’t realize the laxative contained licorice. His doctor didn’t ask. That’s how quietly this danger creeps in.

Healthcare guidelines from the MSD Manual and Merck Manual now explicitly warn: “Patients taking digoxin should avoid licorice entirely.” There’s no safe amount if you’re on this drug.

How Much Licorice Is Too Much?

Not all licorice is created equal. Most red licorice in the U.S. and Australia doesn’t contain any real licorice root-it’s just anise-flavored candy. But black licorice, licorice tea, herbal supplements, and traditional remedies often do.

The safety threshold? 100 mg of glycyrrhizin per day. That’s about 60-70 grams of traditional black licorice candy-roughly 2 to 2.5 ounces. Sounds like a lot? Maybe. But people snack on it daily. One pack of licorice twists might contain 20-30 mg. Two packs a day? You’re already over the limit.

And here’s the catch: sensitivity varies. Women, older adults, and people with existing high blood pressure or heart disease are more vulnerable. Some people show signs of toxicity after just 10 days of daily consumption at 50 mg. That’s why the Medsafe bulletin (2019) recommends that anyone with hypertension avoid licorice completely-not just limit it.

What to Look For (and What to Avoid)

Check labels. If a product says “licorice root,” “Glycyrrhiza glabra,” or “licorice extract,” it contains glycyrrhizin. That includes:

• Black licorice candy (especially imported brands)
• Herbal teas labeled as “licorice root tea”
• Dietary supplements for digestion, adrenal support, or “natural energy”
• Traditional Chinese medicine formulas
• Some throat lozenges and cough syrups

Look for “deglycyrrhizinated licorice” (DGL) on labels. That’s licorice with the glycyrrhizin removed. DGL is safe for stomach issues like acid reflux and doesn’t affect blood pressure. But if the label doesn’t say “deglycyrrhizinated,” assume it’s risky.

Also, don’t assume “natural” means safe. Herbal supplements aren’t regulated like pharmaceuticals. There’s no standard for how much glycyrrhizin is in a capsule or tea bag. One brand might have 20 mg per serving; another might have 150 mg. You won’t know unless the manufacturer tests and discloses it-and most don’t.

Signs You Might Be Affected

If you’ve been eating licorice regularly and are on blood pressure meds, watch for these red flags:

• Unexplained rise in blood pressure (even if you’re taking meds as prescribed)
• Swelling in ankles or legs (edema)
• Muscle weakness, cramps, or fatigue
• Irregular heartbeat or palpitations
• Feeling unusually tired or weak
• Headaches or dizziness

These aren’t just “off days.” They’re signs your body is reacting to glycyrrhizin. If you notice any of these, stop licorice immediately and get your potassium and blood pressure checked. A simple blood test can show if your potassium is low (<3.5 mmol/L) and if your cortisol-to-cortisone ratio is elevated-a clear marker of glycyrrhizin exposure.

What to Do Next

If you’re on blood pressure medication:

1. Stop all licorice-containing products-no exceptions.
2. Check every supplement, tea, and candy label for “licorice root” or “Glycyrrhiza glabra.”
3. Ask your pharmacist or doctor if any of your current supplements contain licorice.
4. Get a basic blood panel: potassium, sodium, and renin/aldosterone levels if possible.
5. Track your blood pressure at home for 1-2 weeks after stopping licorice. You may see a drop within days.

Even if you’ve been eating licorice for years without symptoms, it doesn’t mean you’re safe. The damage builds slowly. One study found that people with uncontrolled hypertension who stopped licorice saw their BP drop by 10-15 mmHg within two weeks-even without changing their meds.

Final Thoughts

This isn’t about giving up a favorite treat. It’s about protecting your heart and making sure your medication works the way it’s supposed to. Licorice isn’t a harmless herb-it’s a potent biochemical agent with documented, measurable effects on your body’s salt and fluid balance. For someone managing high blood pressure, that’s not a risk worth taking.

If you love the flavor, switch to DGL products or anise-flavored alternatives. Your blood pressure-and your heart-will thank you.