Frankie Muniz, the former child star of "Malcolm in the Middle", suffered a mini-stroke last week, aged just 26.
The actor was taken to a hospital in Arizona by friends who became alarmed when he developed problems speaking and understanding words, TMZ reported.
ABC News reported the former child star who retired at 19 tweeted: "I was in the hospital last Friday. I suffered a 'mini stroke', which was not fun at all."
"Have to start taking care of my body! Getting old!"
Muniz who has taken a break from acting to play in a band has been told to take it easy.
The Los Angeles Times said a mini-stroke usually occurs in those aged over 55 when blood flow to a part of the brain stops temporarily, and medics regard it as a warning sign for a full stroke.
It can be caused by high blood pressure, a poor diet, smoking or drug taking.
No cause had yet been determined by doctors in Muniz's case, TMZ said.