The government has called the cyberattack "the most serious breach of personal data" that Singapore has experienced.
It posted the warning on his Facebook page just hours after news broke that hackers had stolen the personal particulars of 1.5 million patients in Singapore's worst cyber attack.
The data was stolen over a one-week period from June 27 to July 4.
This is the SMS you will receive if you are one of the 1.5 million people who had their data stolen.
The systematic siphoning of the SingHealth database went undetected for almost three years and Singapore's government has confirmed that the records haven't been tampered with but only copied. And the hackers did not have access to other records, such as diagnosis documents, test results or doctors' notes, the statement said. "We have not found evidence of a similar breach in the other public healthcare IT systems".
Singapore will set up a commission of inquiry to look into the hack and immediately move to strengthen government defenses against cyber attacks, the Ministry of Communications said in a separate statement.
"Investigations by the Cyber Security Agency of Singapore (CSA) and the Integrated Health Information System (IHiS) confirmed that this was a deliberate, targeted and well-planned cyberattack", a government statement said.
While the exact culprits are not known, local media believes it was the work of state-sponsored actors and "not the work of casual hackers or criminal gangs".
The PM added: 'My medication data is not something I would ordinarily tell people about, but there is nothing alarming in it'.
"If so, they would have been disappointed".
But authorities have put the brakes on these plans while they investigate the cyberattack.
It includes names and addresses, as well as prescription information in some instances - potentially allowing a hostile agency the ability to blackmail or otherwise attack the people whose data has been stolen. He said: "With cyber attackers getting better-skilled by the day, it's not surprising to see breaches happen despite our best efforts".
According to the statement, SingHealth lodged a police report on 12 Jul 2018 and police investigation is ongoing.
The company provided a website so customers can check if they were among those affected and is contacting all patients. With threats becoming more complex and top malicious traffic hotspots in Asia-Pacific, including China, South Korea, and Vietnam, he said the government should partner "the wider tech and cybersecurity ecosystem". "We have to go forward, to build a secure and Smart Nation".