Veteran politician Javed Hashmi suffers health problems due to the change in weather conditions, party sources said.
PTI president was shifted to PIMS on Monday after he fell ill and undergoing treatment at the hospital.
The hospital doctors carrying out tests to determine if Hashmi had throat or chest infection.
The PTI has been protesting in Islamabad against alleged rigging in the 2013 elections and demanding Prime Minister Nawaz Sharif to step down.
