Sharif, who has a history of heart disease and suffers from high blood pressure, has been “quite unwell” since Saturday but has been denied the right to see his doctor, according to his party’s spokeswoman Maryam Aurangzeb.
She said: “Caretaker Prime Minister Nasir-ul-Mulk and chief minister of Punjab province Hasan Askari were approached with a request to provide access to Sharif’s personal physician but all requests went down the drain.
“Nawaz Sharif, who is also a heart patient, has been quite unwell since Saturday after his blood pressure went up.”
The former leader of the Pakistan Muslim League-Nawaz (PML-N) party was found guilty of corruption in his absence and jailed for 10 years upon his return to the country on July 13.
Sharif, who led the country until 2017, rejected the allegations and claimed the military were aiding a “judicial witch-hunt” against the PML-N, aimed at preventing it from ruling five more years.
He is widely believed to have returned to Pakistan despite the charges against him to rally his party in the run up to the country’s general elections.
Pakistan citizens are to cast their vote on July 25, amid a close contest between the PML-N and the Pakistan Tehreek-e-Insaf (PTI), led by former cricket star Imran Khan.
Tensions and violence have escalated in Pakistan ahead of the elections.
A series of terrorist attacks targeting politicians claimed the lives of hundreds of civilians.
Siraj Raisani, head of the Balochistan Awami Party, died with 149 other people in a suicide bombing earlier this month.
And at least 20 people, including Haroon Bilour, leader of the Awami National Party, died in another suicide attack in the northwest city of Peshawar.
And fears the election may be rigged rose when PML-N leaders accused Khan of being supported by the country’s powerful military.
The PTI leader denied any links to the military and fired back, condemning the harassment of election candidates.
But the independent Human Rights Commission of Pakistan (HRCP) warned there were “ample grounds to doubt” the legitimacy of the elections and criticised “blatant, aggressive and unabashed attempts to manipulate the outcome of the upcoming elections.”
The group also claimed forces are actively working to help the election of former cricketer Imran Khan, leader of PTI who is allegedly close to the military.
Pakistani authorities launched an anti-terrorism investigation against PML-N leaders right after a pro-Sharif rally, and opened criminal cases against nearly 17,000 party members.