Thousands of people across the city are to be quizzed on their health in a survey aimed at helping officials draw up policies, develop services and allocate resources effectively.

The Centre for Health Protection (CHP) on Friday said it will launch its Population Health Survey on September 18, the fourth such exercise since 2003.

Officials will randomly select about 20,000 people aged 15 and above to fill out a questionnaire on a voluntary basis, while around 1,800 of those chosen will also be invited to undergo a free health examination.

The questionnaire covers a range of information, including physical and mental health status, health behaviour and preventative practices, with the data to be used to help authorities identify trends and develop disease prevention strategies.

"[The data] also helps us strive with our new intervention efforts and to be more focused in our resource allocation and our health promotion activities," said Dr Geeta Sharma, Principal Medical and Health Officer in the CHP's non-communicable disease branch.

The medical examination will involve recording people's physical measurements, as well as taking blood and urine samples.

Tests on the samples will cover things such as glucose levels, iron status and checks for viral hepatitis. Participants will receive their laboratory reports, along with referral letters if there are any abnormal tests results.

Officials said those who take part in the survey will be given supermarket vouchers worth between HK$100 and HK$300.