Several widely available herbs and herbal supplements can cause heart palpitations, either on their own or by interacting with medications. Some act as stimulants that directly speed up your heart rate. Others disrupt your body’s electrolyte balance or amplify the effects of heart drugs in dangerous ways. The most commonly reported include bitter orange, guarana, licorice root, St. John’s wort, ginseng, and ephedra (now banned in the U.S.).
Stimulant Herbs That Speed Up Heart Rate
The most straightforward way an herb triggers palpitations is by acting like a stimulant, revving up the same “fight or flight” pathways that adrenaline uses. Bitter orange is one of the most well-documented offenders. It contains a compound called synephrine, which is marketed for weight loss because it increases your metabolic rate. The problem is that synephrine doesn’t just target fat cells. It also stimulates receptors in the heart that control heart rate and blood pressure. Case reports of cardiovascular events have been linked to synephrine doses as low as 12 mg, though doses in reported adverse events have ranged up to 100 mg.
Guarana is another stimulant herb, popular in energy drinks and pre-workout supplements. Its seeds contain up to 5.3% caffeine by weight, roughly 25 times the concentration found in espresso coffee. At moderate intake levels (under 400 mg of caffeine per day from all sources), the cardiovascular risk is low. But guarana is often stacked with other stimulants in supplement blends, pushing total caffeine intake well past that threshold without the user realizing it.
Ephedra deserves mention even though the FDA banned it from dietary supplements. A review of 140 adverse event reports submitted to the FDA found that 47% of events linked to ephedra supplements involved cardiovascular symptoms. Palpitations and rapid heart rate were the second most common complaint, after high blood pressure. Ten cases resulted in death and 13 caused permanent disability. Ephedra alkaloids activate the same adrenaline-like pathways as bitter orange, but more aggressively. You can still encounter ephedra in products sold outside the U.S. or marketed as traditional remedies.
Licorice Root and Electrolyte Disruption
Licorice root causes palpitations through a completely different mechanism: it drains potassium from your body. An active compound in licorice blocks an enzyme in your kidneys, essentially tricking your body into behaving as if it’s producing too much of a hormone called aldosterone. The result is that your body retains sodium and flushes potassium. Low potassium is one of the most reliable triggers for abnormal heart rhythms.
This isn’t a theoretical risk. In one published case, a woman who took licorice-containing herbal medicine for chronic constipation over two months developed potassium levels of 1.5 mmol/L, dangerously below the normal range of 3.5 to 5.0. She experienced life-threatening irregular heart rhythms that required defibrillation. The risk is highest with long-term, daily use of actual licorice root or supplements containing glycyrrhizin (the active compound). Most licorice-flavored candy in the U.S. uses artificial flavoring and doesn’t carry the same risk, but imported licorice products and herbal preparations often contain the real thing.
St. John’s Wort
St. John’s wort is one of the top-selling herbal supplements for depression, anxiety, and sleep problems. It can cause palpitations in two distinct ways. First, it appears capable of triggering a fast heart rhythm on its own. In one documented case, a 33-year-old woman with no prior heart problems developed recurrent episodes of palpitations one month after starting St. John’s wort for depression. She was diagnosed with supraventricular tachycardia, a type of abnormally fast heartbeat originating in the upper chambers of the heart. Her symptoms resolved completely after she stopped taking the supplement.
Second, St. John’s wort is one of the most prolific drug interactors in the herbal world. It changes how your liver processes dozens of medications, including many heart drugs. If you take a heart rhythm medication and add St. John’s wort, the supplement can either increase or decrease the drug’s effective concentration in your blood, both of which can destabilize your heart rhythm.
Ginseng, Hawthorn, and Heart Drug Interactions
Ginseng and hawthorn are both marketed for cardiovascular health, which makes their risks especially tricky. Both can amplify the effects of a class of heart medications called cardiac glycosides (the most common being digoxin). If you’re taking digoxin to control a heart rhythm problem and you add ginseng or hawthorn, the combination can push the drug’s effect past its safe range and actually provoke the arrhythmia it was meant to prevent.
Aloe vera (taken orally, not applied to skin) carries the same interaction risk with cardiac glycosides. So does a Chinese herb called sanchi. The pattern is consistent: herbs that affect how your heart cells handle minerals like potassium, sodium, and calcium can become dangerous when layered on top of drugs that target those same pathways.
Less Common but Potentially Dangerous Herbs
Several herbs carry serious arrhythmia risks but are less commonly encountered in everyday supplements:
- Aconite: Used in some traditional Chinese and Ayurvedic preparations, aconite directly alters how heart muscle cells handle sodium, increasing the heart’s tendency to fire erratically. The American Heart Association specifically flags aconite alkaloids as a cause of drug-induced arrhythmia.
- Oleander: Every part of this plant is toxic. It increases the risk of heart block, dangerously high potassium levels, arrhythmia, and death. Oleander poisoning can occur from teas, supplements, or even accidental exposure.
- Lily of the valley: Contains compounds similar to digoxin. It intensifies the effects of several classes of heart medications, including beta-blockers and calcium-channel blockers.
- Horny goat weed (epimedium): Marketed for sexual health, it has reported arrhythmia-triggering effects.
- Rhodiola and Echinacea: Both have documented arrhythmogenic potential, though palpitations from these herbs appear to be rare at typical supplement doses.
- Ginkgo biloba: Widely used for memory support, it has been linked to heart rhythm disturbances, particularly in combination with other medications.
Ashwagandha and Thyroid-Related Palpitations
Ashwagandha doesn’t directly stimulate the heart the way bitter orange or guarana does, but it can cause palpitations through a side door. Ashwagandha has thyroid-stimulating properties, and in people who already have an overactive thyroid or are borderline hyperthyroid, it can tip the balance into full-blown symptoms: rapid heartbeat, tremors, restlessness, and nervousness. If you’ve noticed palpitations after starting ashwagandha, the supplement may be pushing your thyroid function higher than your body can comfortably handle.
Why “Natural” Doesn’t Mean Safe for Your Heart
Herbal supplements aren’t regulated the same way prescription drugs are. They don’t need to prove safety or effectiveness before hitting store shelves, and the actual contents of a supplement can vary significantly between brands or even between batches. The European Society of Cardiology’s 2025 guidelines reinforce this reality, stating that dietary supplements lacking documented safety data are not recommended for reducing cardiovascular risk.
The risk of palpitations from herbs increases sharply in three situations: when you combine multiple supplements (especially stimulant-containing ones), when you take herbs alongside prescription heart medications, and when you use herbs at high doses or for extended periods. Licorice taken for two months caused life-threatening arrhythmia. St. John’s wort caused palpitations within one month. Ephedra caused permanent injury in some users. These aren’t risks that take decades to surface.
If you’re experiencing palpitations and you take any herbal supplement, the supplement should be one of the first things you evaluate. Persistent rapid heart rate, episodes of racing heartbeat lasting more than a few seconds, lightheadedness, or fainting alongside palpitations are signals that something more than a benign flutter is happening. The American Heart Association recommends that anyone taking substances with arrhythmia potential monitor their pulse or heart rate daily, and a simple wearable device can make that easy to do at home.