undiagnosed

adjective

un·​di·​ag·​nosed ˌən-ˌdī-ig-ˈnōst 

-əg-, 

-zd

: not diagnosed : not identified through diagnosis

an undiagnosed illness

… the symptoms of the syndrome may be subtle and thus may remain undiagnosed.

—Dwight R. Robinson

a condition that often goes undiagnosed

Examples of undiagnosed in a Sentence

Recent Examples on the Web

Many seem to struggle with undiagnosed mental-health issues and some appear to be trapped in dangerous and possibly criminal situations. — Brady Brickner-Wood, New Yorker, 28 Sep. 2026

Hepatitis C infection can often go undiagnosed for years, if not decades, due to lack of symptoms. — Mason Leib, ABC News, 8 Sep. 2026

In 1995, the death of 16-year-old John Marshall, who suffered a heart attack deriving from an undiagnosed condition known as arrhythmogenic right ventricular cardiomyopathy, proved to be a line-in-the-sand moment. — Jordan Campbell, New York Times, 6 Sep. 2026

Unraveling Medical Mysteries Patients with undiagnosed conditions suffer not only from their symptoms but also from the uncertainly of not knowing what afflicts them. — The New York Review of Books, 5 Sep. 2026

Word History

First Known Use

1864, in the meaning defined above

Medical Definition

undiagnosed

adjective

un·​di·​ag·​nosed -ˈnōst 

: not diagnosed : eluding diagnosis

undiagnosed disease