Health workers including midwives, nurses, paramedics, radiographers and cleaners are taking further industrial action over pay.
Trade union members will walk out for four hours today (24 November) between 7am and 11am.
The strike action is taking place after the government rejected a 1% pay rise recommended by an independent NHS pay review body.
The strike action will be followed by six days of employees working to rule, during which time workers from 10 trade unions will join members of the Unison union.
Dave Prentis, general secretary at Unison, said: “If the secretary of state seriously thinks staff are the NHS’ best asset, then he needs to treat them fairly.
”We are only asking for decent pay for the hardworking people the government says it cares so much about.
“The government and NHS employers need to engage in meaningful talks about how to resolve this dispute.”
Jeremy Hunt, secretary of state for health was unavailable for comment.