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

Have you ever enjoyed a piece of black licorice candy, sipped on licorice tea, or taken a herbal supplement labeled "licorice root" while also taking medication for high blood pressure? If so, you might be at risk for a serious, often overlooked interaction that can make your blood pressure medication less effective-or even dangerous.

How Licorice Affects Your Blood Pressure

Licorice root contains a compound called glycyrrhizin, which is responsible for its sweet flavor. But glycyrrhizin doesn’t just taste sweet-it acts like a hormone in your body. Specifically, it mimics aldosterone, a natural hormone that tells your kidneys to hold onto salt and water while flushing out potassium.

This sounds harmless until you realize what that does to your blood pressure. More salt and water in your bloodstream means higher blood volume, which raises your blood pressure. At the same time, losing potassium can cause muscle weakness, irregular heartbeat, and even heart rhythm problems. This effect isn’t mild-it’s measurable. Studies show that people who consume more than 100 mg of glycyrrhizin per day (about 60-70 grams of licorice candy) experience an average increase of 5.5 mmHg in systolic blood pressure and nearly 2 mmHg in diastolic pressure.

That might not sound like much, but for someone already struggling to control hypertension, that small rise can be enough to undo weeks of medication work. And it’s not just about candy. Licorice is also found in herbal teas, supplements, and even some tobacco products. Many people don’t realize they’re consuming it.

Why It Interferes With Blood Pressure Medications

Most blood pressure medications work by helping your body get rid of extra fluid or relaxing your blood vessels. But licorice does the opposite. It makes your body hold onto fluid and lose potassium. That’s why it directly fights against the effects of:

• Diuretics (like hydrochlorothiazide or furosemide): These are meant to flush out salt and water. Licorice makes your body hold onto them, reducing the drug’s effectiveness.
• ACE inhibitors (like lisinopril or captopril): These lower blood pressure by relaxing blood vessels and reducing fluid buildup. Licorice increases fluid, making these drugs work harder-or not at all.
• Potassium-sparing diuretics (like spironolactone): These are designed to keep potassium levels up. Licorice drains potassium, creating a dangerous imbalance.
• Digoxin (Lanoxin): This heart medication becomes dangerously toxic when potassium levels drop too low. Licorice can trigger digoxin toxicity, leading to heart failure-even in people who’ve taken it safely for years.

The mechanism behind this is well-documented: glycyrrhizin breaks down into glycyrrhetic acid, which blocks an enzyme in your kidneys called 11β-HSD2. Normally, this enzyme protects your body from being overstimulated by cortisol (a stress hormone). When it’s blocked, cortisol acts like aldosterone-and that’s what causes the salt retention and potassium loss.

Who’s Most at Risk

Not everyone who eats licorice will have problems. But certain groups are far more vulnerable:

• People over 60: Aging kidneys are less able to handle the extra sodium load.
• Women: Studies show women are more sensitive to glycyrrhizin’s effects, even at lower doses.
• People with existing hypertension: If your blood pressure is already hard to control, licorice can push it out of range.
• Those with heart disease or kidney problems: These conditions make your body less able to compensate for fluid and electrolyte shifts.

One case study published in Cardiology followed an older man who developed congestive heart failure after taking a herbal laxative containing licorice. He was on digoxin. His potassium dropped to 2.8 mmol/L (normal is 3.5-5.0). He needed emergency treatment. He didn’t know the laxative contained licorice.

How Much Is Too Much?

The safe limit? 100 mg of glycyrrhizin per day. That’s the threshold recognized by health agencies worldwide, including Medsafe in New Zealand and the Merck Manual.

But here’s the catch: you can’t tell how much glycyrrhizin is in most products. A single piece of black licorice candy can contain 5-15 mg of glycyrrhizin. So eating 10 pieces a day puts you over the limit. Licorice tea? One cup can have 10-30 mg. Supplements? Some contain 100-200 mg per serving.

And here’s another problem: many products labeled "licorice" don’t actually contain glycyrrhizin. In the U.S., most red licorice is flavored with anise, not licorice root. But black licorice? It’s often real. And herbal supplements? They’re rarely labeled clearly. The FDA doesn’t require manufacturers to list glycyrrhizin content.

Signs You Might Be Having a Reaction

If you’re taking blood pressure meds and start noticing these symptoms, stop eating licorice and talk to your doctor:

• Unexplained rise in blood pressure (even if you’ve been taking meds regularly)
• Muscle weakness, cramps, or fatigue
• Irregular heartbeat or palpitations
• Swelling in your legs or ankles (edema)
• Feeling unusually tired or sluggish

Doctors can test for this. A blood test showing low potassium (below 3.5 mmol/L) combined with high cortisol and low aldosterone levels is a classic sign of licorice-induced pseudoaldosteronism. Your blood pressure might drop quickly once you stop consuming licorice-sometimes within days.

What to Do Instead

If you enjoy the taste of licorice, you have options:

• Choose deglycyrrhizinated licorice (DGL): This is licorice with the glycyrrhizin removed. It’s used for digestive issues and doesn’t affect blood pressure.
• Read labels carefully: Look for "anise flavor" instead of "licorice root extract." Avoid anything that says "Glycyrrhiza glabra" or "licorice root."
• Ask your pharmacist: If you’re taking a supplement, ask if it contains licorice root. Most won’t know-but it’s worth asking.
• Switch to alternatives: Try herbal teas like chamomile, peppermint, or rooibos. They’re naturally sweet and safe.

And if you’ve been consuming licorice regularly and are on blood pressure medication, don’t just cut back-talk to your doctor. They may want to check your potassium levels and adjust your meds.

Bottom Line

Licorice isn’t just a candy. It’s a powerful bioactive substance that can interfere with your medications in ways you can’t see or feel until it’s too late. For people with high blood pressure, even small amounts over time can undo the benefits of their treatment. The science is clear: if you’re on blood pressure medication, avoid licorice root in all its forms-candy, tea, or supplements-unless it’s labeled as deglycyrrhizinated.

Your blood pressure is too important to risk. A few pieces of candy aren’t worth a hospital visit.