The rise in cases across China follows the rollback of its strict “zero Covid” policies, which kept infection rates low but fuelled public frustration and crushed economic growth.
The testing applies to anyone two years and older.
Other countries have taken similar steps in an effort to keep infections from spreading beyond China’s borders.
Beijing-based doctor Ning, who only gave his surname, told the Financial Times: “We can work hard, we can work overtime, but at the end of the day, medical staff, like others, are made of flesh, not iron.
“No matter how dedicated we are, we have physical and mental limits.”
China kept case numbers low for two years with a “zero-Covid” strategy that isolated cities and confined millions of people to their homes.
Now, as it backs off that approach, it is facing the widespread outbreaks that other countries have already gone through.
China only counts deaths from pneumonia or respiratory failure in its official Covid-19 toll, a health official said last week.
That unusually narrow definition excludes many deaths other countries would attribute to Covid-19.
Experts have forecast 1 to 2 million deaths in China through the end of 2023.