The American singer's Beautiful Trauma world tour was due to hit Sydney on Friday but she cancelled that first show on doctor's orders.

She battled through a Saturday night show but on medical advice postponed Monday night's concert just hours before it was due to start at Qudos Bank Arena.

Early Tuesday morning another postponement was announced for the August 7 show.

Promoter Live Nation said on Twitter that Pink was admitted to hospital in Sydney on Sunday night suffering from dehydration and was treated and discharged but was readmitted on Monday and diagnosed with a gastric virus.

"Pink will remain in hospital overnight, continuing her treatment and recovery," the tweet said.

Both the Friday and Monday night shows are expected to be rescheduled.

All other performances on the Australian leg of Pink's Beautiful Trauma tour will go ahead as scheduled, Ticketek said in a tweet on Monday.

Pink kicked off her latest Australian tour in Perth from July 4. She then played in Adelaide before Sydney where further shows are scheduled on August 9, 11, 12, 25 and 26.

She's also due to perform seven shows in Brisbane between August 14 and 23 followed by Melbourne on August 28 and 29.

Pink last toured Australia in 2013 when she performed 46 shows as part of her Truth About Love world tour.

Australian Associated Press