One day, Hanna Zechzer got a flier in the mail advertising an herbal pill to help her lose weight. The testimonials said the product was "all natural," so she thought it was safe. The leaflet sat for a few days, then she ordered a bottle.

For a week Zechzer took three tablets a day of EZ Trim, with each tablet containing 333 milligrams of ma huang, a natural source of the weight-loss supplement ephedra, and 250 milligrams of guarana, a source of natural caffeine.

Ephedra and its alkaloids are among the most popular diet supplements in the country, but health care providers say they are also among the most dangerous, capable of inducing adverse reactions ranging from uncomfortably sweaty palms to heart failure and sudden death.

Zechzer, then 42, a dentist's assistant in Watertown, Wis., and a single mother of three children, had a bit of an upset stomach early in the week, but it was different by Thursday.

"I got real jittery, and I couldn't work," she said. Her pulse was normal, but she took her blood pressure and found it was 150/100. "I had a really bad headache, a tingling sensation in my left arm and pressure in my chest."

She lowered a dentist's chair and lay down. She was very cold, she said, "and I was thinking 'I wish someone would take care of me.' " That was the last thing she remembered for four days in July 1998.

According to a journal compiled by Zechzer's sisters, her co-workers called the emergency service almost immediately, but by the time they arrived Zechzer was in the middle of a grand mal seizure. She was in and out of consciousness, combative and flailing her arms.

She was taken to a nearby hospital and put on life support. Doctors found amphetamines in her blood. Was Zechzer taking speed? No, her sisters said. But her daughters remembered the diet supplement. Ephedra is a close chemical cousin of the illegal drug methamphetamine.

Over the weekend an ambulance moved Zechzer to St. Mary's Hospital in Madison. Her physician started reading about ephedra. Zechzer's heart was failing, and doctors didn't know what to do about it. They began talking about a heart transplant. "It was a minute-to-minute thing," Zechzer said.

By Monday, though, she was having periods of coherence, and was writing notes in response to questions from nurses. She remembers none of it. "My sisters kept telling me to trust them," she said, but she was confused and terrified.

"What happened?" reads one of her notes. "What's the diagnosis?" "Might need a heart transplant." "Scared a lot."

By Tuesday, she was feeling better. She learned about the ephedra, and her rage began to grow. At 10 Tuesday evening she asked, "Can they call that [expletive] company?" Ten days after the seizure they removed her respirator.

In all, Zechzer was hospitalized for two weeks, but, "by the grace of God, I had no heart damage." A lawyer is preparing to file suit on her behalf. Distributors of EZ Trim refused to comment on Zechzer's story.