Hamilton. AFP PHOTO

Seven-time Formula One world champion Lewis Hamilton withdrew from a tyre test with Ferrari in Italy to be with his sick dog, he revealed on social media on Friday.

Posting on Instagram, Hamilton said his 12-year-old bulldog Roscoe had been hospitalised with pneumonia and was now in a coma.

"Roscoe caught pneumonia again and was struggling to breathe," the 40-year-old British driver wrote.

"He was admitted into hospital and sedated to calm him while they did checks on him and during the process his heart stopped.

"They managed to get a heartbeat back and now he's in a coma. We don't know whether he will wake from this."

Roscoe, who was adopted by Hamilton in 2013, has his own Instagram account with 1.3 million followers.

Hamilton, who finished eighth in last weekend's Azerbaijan Grand Prix, was due to do a tyre test in Mugello but was replaced by Ferrari's reserve driver Zhou Guanyu.