President Trump went far beyond the science when, based on an unproven link and inconclusive studies, he warned last month that taking the pain reliever acetaminophen, the active ingredient in Tylenol, during pregnancy caused autism.

But for decades, doctors and scientists have sounded an alarm about a different risk associated with acetaminophen products that is well established: liver damage from accidentally overdosing on the drug.

Experts emphasize that acetaminophen is safe when taken as directed. But when people take too much, either intentionally or unintentionally, it can cause such serious injury to the liver that it can lead to hospitalization, a liver transplant or even death.

Every year, a few hundred Americans die from liver failure from unintentionally taking too much acetaminophen, often because, while struggling with pain, they lose track of how much they have taken, according to medical researchers. Suicides involving acetaminophen account for additional deaths.

Relative to the number of people who take acetaminophen, the number of overdoses is very small. But because billions of doses of the drug are taken by Americans each year, acetaminophen overdoses are nevertheless the leading cause of acute liver failure.

“I think it’s an acceptably safe medication,” said Dr. Timothy Davern, a liver specialist in San Francisco who treats people with severe liver injury or acute liver failure from acetaminophen poisoning. “But if it’s used in higher doses, we’re all susceptible to liver injury from that. The consequences can be devastating.”