More Australians than usual are expected to be ill on Friday after celebrating Australia Day, prompting employer groups to plead that workers take annual leave instead of a sickie, while unions say there are bigger issues to worry about.

Paul Dundon, the managing director of Direct Health Solutions, estimates $54 million will be lost from the Australian economy on Friday.

Employer groups are concerned many Australians will take a sickie on Friday and head to the beach as part of an extended Australia Day long weekend.

"Sick leave will rise from an average of 3.5 per cent of workers each day to 5 per cent when there is an opportunity to extend the Australia Day break to a long weekend," Mr Dundon said.

"This increase represents a jump in sick leave of 42 per cent compared to the average.