People have been urged to only head to accident and emergency departments at Norfolk's hospitals if absolutely necessary this bank holiday weekend, with nurses taking part in strikes.
Health bosses have advised using health and care services wisely to ensure care is available to patients who need it most during the May Bank Holiday.
Bosses at NHS Norfolk and Waveney said health and care services are seeing high levels of demand already.
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And members of the Royal College of Nursing will be taking part in industrial action from 8pm on Sunday (April 30) until just before midnight on Monday, May 1 in their long-running dispute over pay.
That has triggered cancelled appointments, but health chiefs have also urged people not to go to A&E departments unless absolutely necessary and to call NHS 111 first, or 999 in the case of life-threatening emergencies.
Tricia D'Orsi, executive director of nursing at NHS Norfolk and Waveney, said: “We understand people will be concerned appointments are having to be re-arranged and that this can cause disappointment.
"We are working hard to make sure emergency services, and those which need to be prioritised, maintain safe standards of care."
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