Calgary Laboratory Services says people who show up without appointments are going to have to wait longer for their medical tests.

The company recently added an online booking system to complement the telephone booking service, which has been in place for over a year.

Patients with appointments will be given priority over those who simply walk-in, company officials said.

"And we're hoping that patients will take advantage of that. And we actually hope up to 80 per cent of our patients will book appointments," said Paula Hall, CEO of Calgary Laboratory Services, which provides diagnostic lab testing services on behalf of Alberta Health Services.

Some patients become frustrated when they realize service is not provided on a first-come, first-served basis, Hall said.

"I wouldn't say people have objected, but what happens is, people aren't aware of the patient appointment process, so they wonder why people are being taken not necessarily at the time of arrival," she said.

"And that's what we want to get the message out to everyone that patient appointments are the way that we really would like to see our patients in the future."

CLS aims to see all patients who book ahead within 15 minutes of their appointment time, Hall said.