Manziel said in February that he had bipolar disorder, and he tweeted Tuesday that an increase in his Lithium dose had caused the reaction.
Former NFL quarterback Johnny Manziel was reportedly hospitalized Monday evening in Texas following a concert after having a negative reaction to a prescription medication.
"It was a scary moment and I'm especially grateful for the staff at the hospital and all that they've done in the last 24 hours", Manziel said on Instagram.
Johnny Manziel is trying to get back to the NFL. Manziel revealed that he was diagnosed about a year ago and he is taking medication for the condition.
Manziel, 25, is attempting an NFL comeback after not playing in the league since 2015. Earlier this year, Manziel was working out in College Station at Texas A&M's pre-draft pro day in front of team scouts.
Over the last few months, Manziel has also been upfront about his failure as an National Football League quarterback.