Sinha was admitted to Kokilaben Dhirubhai Ambani Hospital Monday afternoon following respiratory allergic reaction.
"Mr Shatrughan Sinha is improving now. His condition is stable. But he will be still in the hospital tonight, " Ram Narain, COO, Kokilaben Hospital, told.
However, the doctor said Sinha's discharge date has not yet been finalised.
"I can't say the exact time when we will discharge him. Tomorrow we will assess him and then we will take a call, " said Narain.
The 66-year-old's daughter, actress Sonakshi Sinha too tweeted about her father's health, saying he is hale and hearty.
"Making moutains out of mole hills (baat ka batangadh) about someones health is NOT cool. My father is hale and hearty and waiting for me at HOME and not in the ICU (Intensive Care Unit) as some people are claiming on TV right now. Thanks for the concern, but pls... KHAMOSH!!" Sonakshi tweeted.
The veteran actor's wife Poonam and his sons Luv and Kush were with him at the hospital.
Known for films like "Kalicharan", "Blackmail", "Dostana" and "Shaan", Sinha later ventured out from films into politics. He is the Bharatiya Janata Party MP from Patna Saheb, Bihar.