719 thousand Bulgarian citizens are are not health-insured.  This is the official data by the end of 2017 by the Bulgarian Health Ministry. 

Currently a process is underway to prepare the assessment for the health-insured Bulgarian citizens for 2018, which is not yet complete.

A full assessment was made in 2017. According to it, Bulgarian citizens, who are subject to compulsory health insurance in the country but who are not insured by the end of 2017, are about 719 thousand.

For the period 2011-2017 the number of non-health-insured Bulgarians remains stable. The highest figure was registered in 2013 when 839,000 people didn’t have health insurance.

After this peak, there was a serious decline of almost 200,000 people, with the lowest figure for the period being recorded 2 years later in 2015. 

Source