Foxglove is extremely toxic. Every part of the plant contains cardiac glycosides, compounds that directly interfere with your heart’s ability to maintain a normal rhythm. Eating even a small number of leaves can push blood levels of these compounds into a potentially lethal range. One documented case involved a woman who ate just five foxglove leaves in a pie (she’d mistaken them for borage) and developed blood levels considered potentially fatal.
What Makes Foxglove Dangerous
Foxglove produces over a hundred different cardiac glycosides, with digitoxin and gitoxin being the most prominent in the common garden species (Digitalis purpurea). These compounds block a critical pump in heart muscle cells that regulates sodium and potassium. When that pump is disabled, calcium builds up inside the cells, forcing the heart to contract more powerfully than it should. In small, carefully controlled pharmaceutical doses, this effect has been used to treat heart failure for centuries. In uncontrolled amounts from eating the plant, it overwhelms the heart and causes dangerous rhythm disturbances.
The toxins are present in the leaves, flowers, seeds, and stems. There is no safe part of the plant to handle with bare hands and then touch your mouth, and no safe amount to eat. Even water in a vase holding cut foxglove stems has caused poisoning. The concentration of glycosides varies between individual plants, between seasons, and between species of foxglove, which makes it impossible to estimate a “safe” quantity.
How Poisoning Progresses
Symptoms typically begin with the gut. Within a few hours of ingestion, nausea and vomiting are common. This is actually the body’s attempt to expel the toxin, and early vomiting may limit how much gets absorbed. But if enough glycosides reach the bloodstream, more serious effects follow.
In one well-documented case, a woman who drank foxglove tea vomited several times within hours, then woke the next morning, roughly 17 hours after ingestion, with severe abdominal and chest pain and a dangerously slow heart rate. By the time she reached the emergency department, her pulse had dropped to 58 beats per minute and she required intensive care monitoring.
The full spectrum of symptoms includes:
- Gastrointestinal: nausea, vomiting, abdominal pain, diarrhea
- Cardiac: slow heart rate (bradycardia), irregular rhythms, heart block, and in severe cases, cardiac arrest
- Neurological: dizziness, confusion, altered consciousness
- Visual: a distinctive yellow or green tint to vision, light sensitivity, and visual hallucinations
The visual changes are particularly unusual and sometimes serve as an early warning sign. The yellow-tinted vision, called xanthopsia, is caused by the toxin acting on receptors in the retina. One case report described a man whose yellow vision led to multiple traffic accidents before he was diagnosed with cardiac glycoside toxicity.
How Much Is Lethal
There is no reliable “lethal dose” measured in number of leaves because toxin concentration varies so widely from plant to plant. What the medical literature does tell us is that blood levels of the glycosides above 10 micrograms per liter are considered potentially lethal. The woman who ate five leaves in a pie reached 10.4 micrograms per liter, placing her squarely in the life-threatening range. She survived, but only with hospital treatment.
Children are at significantly higher risk because of their smaller body weight. A dose that might cause only gastrointestinal symptoms in an adult could be fatal in a toddler. The same applies to elderly adults or anyone with pre-existing heart conditions, where even a small amount of cardiac glycoside can tip an already vulnerable heart into a fatal arrhythmia.
Diagnosing Foxglove Poisoning
Diagnosis is primarily clinical, meaning doctors rely on the combination of symptoms and a known or suspected history of plant exposure. Blood tests can detect cardiac glycosides, but there’s an important catch: the standard hospital test measures digoxin (the pharmaceutical drug), and foxglove contains a mix of related but different compounds. These compounds cross-react unpredictably with the test, so the number it returns doesn’t reliably reflect how poisoned someone actually is. A very sick patient might show a deceptively low reading, or vice versa.
This means doctors treat based on symptoms and heart rhythm changes rather than waiting for or relying on a specific lab number. If you or someone you’re with has eaten any part of a foxglove plant, that information is the single most important thing to communicate to emergency services.
How Foxglove Poisoning Is Treated
An effective antidote exists. It’s made from antibody fragments that bind to cardiac glycosides in the bloodstream and neutralize them. In clinical studies, 93% of patients had their toxicity fully resolved within 20 hours of receiving this antidote, and nearly half improved within just four hours. Heart rhythm abnormalities visible on monitors began correcting within four hours in two-thirds of treated patients.
The antidote is delivered through an IV over at least 30 minutes, or as a rapid injection if cardiac arrest is imminent. In some cases a second dose is needed if symptoms return. The treatment itself can cause a temporary drop in heart function because removing the glycosides also removes their stimulating effect on the heart, so patients are closely monitored throughout.
The key factor in survival is getting to a hospital quickly. Foxglove poisoning is highly treatable when caught in time, but the window matters. Cardiac arrhythmias can deteriorate rapidly, and the progression from slow heart rate to heart block to cardiac arrest can happen without much warning.
Risk to Pets and Livestock
Foxglove is toxic to dogs, cats, and horses. The ASPCA lists it as a plant that can cause cardiac arrhythmias, vomiting, diarrhea, weakness, cardiac failure, and death in all three species. The same cardiac glycosides that affect humans work identically in animals, and pets are at higher risk because of their smaller size. Dogs and cats who chew on foxglove leaves or drink water from a container holding the cut flowers can absorb enough toxin to develop serious symptoms. If you grow foxglove and have pets, placing the plants in areas your animals cannot access is the most practical precaution.
Common Scenarios for Accidental Poisoning
Most foxglove poisonings are accidental. The plant’s leaves look similar to several edible species, particularly borage and comfrey, and cases of mistaken identity appear regularly in the medical literature. Foxglove leaves are large, soft, and slightly fuzzy, which contributes to the confusion. In its first year of growth, before the distinctive bell-shaped flowers appear, the plant is especially easy to misidentify.
Other reported scenarios include children picking and chewing on the brightly colored flowers, adults brewing tea from the leaves (sometimes intentionally as a folk remedy, not realizing the danger), and contamination of herbal preparations with foxglove material. The flowers are attractive to children precisely because they look inviting, with spotted patterns inside the bells that seem designed to draw attention. If foxglove grows in a yard where children play, removing it or fencing it off is worth considering seriously.