"Abdulhadi is continuing with the hunger strike he began on August 25" in Jaw prison near Manama, said lawyer Mohammed al-Jishi.
The prisoner's condition was "stable even though he suffered from hypotension two days ago" said Jishi of the last time he saw his client.
Hundreds of Shiites have been arrested and many have faced trials over their role in anti-regime protests that erupted in February 2011, AFP reported.
Jailed for life for plotting to overthrow the monarchy, 54-year-old Khawaja staged a 110-day hunger strike in 2012 over his imprisonment.
Bahraini authorities said they will continue to monitor Khawaja's health.
Since the start of his hunger strike, a doctor has seen Khawaja "17 times" in five days, the interior ministry's Ombudsman Office said in a statement reported by official BNA news agency.
BNA also said Khawaja sent a letter to the prison authorities saying that "he would go on a hunger strike until he is released".
Khawaja is among defendants handed lengthy jail sentences for their role in the 2011 protests. Seven of them, including Khawaja, have been jailed for life while another seven remain at large.