Queensland’s worst flu season in five years is putting an unprecedented strain on services.

The state has seen a 13 per cent increase in calls to triple-0, with about 19,200 cases of the flu reported this year, including about 2,145 hospitalisations in recent weeks.

The Queensland Ambulance Service (QAS) has reported experiencing experienced eight of its 10 busiest days on record for Code 1 incidents.

The biggest spike in calls has been for most critical Code 1 cases, with a 22 per cent increase in the past week compared to the same period last year.

QAS Acting Commissioner Dee Taylor-Dutton said the heavy workload is expected to continue.

“In 2017 we've seen unprecedented demand for our ambulance services over the flu period,” she said.

“Despite the unprecedented demand increases, we've continued to be able to respond to our most critical patients in a timely manner.”

Meanwhile, Queensland pharmacies are running out of the anti-viral drug Tamiflu.

Tamiflu can lessen the severity and duration of the flu, particularly for the young, elderly and patients with other chronic diseases like asthma.

Several pharmacy chains have reportedly run out of prescription drug and do not expect fresh supplies until mid-September.

The Pharmacy Guild of Australia Queensland's Chris Owen says hospital emergency supplies are in good shape, but Tamiflu will otherwise be hard to find.

“It needs to be taken within the first three days of getting the flu so you need to get onto it quick if you have a script,” he said.

The guild says supplies may have to be shipped in from interstate or overseas.