Jack Blades, 16, collapsed at a house party and his family had been keeping a bedside vigil and praying he pulled through.
Jack, of Airdrie, Lanarkshire, had remained seriously ill in the town’s Monklands Hospital but his sister Lauren said he had woken up.
She took to Facebook to announce her relief and revealed he had been ‘smiling’.
She wrote: “My baby bro is awake and has a smile on his face already!! Could not be happier right now.”
Friends flooded the site with messages in support of Jack and his family.
Her post received over 300 likes within minutes of being posted on Wednesday lunchtime.
Friend Caitlin Hamill posted: “So glad Jack has pulled through! Wee fighter xxx.”
Gemma Fagan wrote: “God bless you’s all Lauren that’s great news my heart go’s out to you and your family x”
And Catherine McCabe said “Omg Lauren brilliant news, gave my shivers reading this so glad thinking of you all.”
A spokesman for NHS Lanarkshire last night described Jack’s condition as stable.
Jack’s family, including his mother Sharon Aitken, 39, had held a beside vigil at his bedside.
Jack and a 17-year-old friend were rushed to hospital at 11.30pm on Saturday after collapsing at a party.
The older boy was later released from hospital.
Police said they believed the pair had taken illegal drugs, including ecstasy and possibly a Mortal Kombat tablet.
Detectives arrested a 16-year-old boy in connection with the incident he was later freed from custody pending further enquiries and did not appear in court
Mortal Kombat pills feature the image of a dragon and the red tablets have been linked to the death of 17-year-old Regane MacColl.
The schoolgirl from Duntocher, Dunbartonshire, is thought to have taken one of the tablets at The Arches nightclub in Glasgow on February 1.
Police have made eight arrests across Scotland as part of a crackdown on the deadly pills.