Almost 22,500 callers waited for more than an hour for the NHS 24 service in September 2021, compared to just 549 in the same month the previous year.
No callers waited this long in September 2019, according to figures obtained by the Scotsman via Freedom of Information request.
September 2021 also saw just seven per cent of calls answered within 30 seconds, compared to 40 per cent in 2020.
The service has seen an increase in demand of up to 50 per cent since the start of the pandemic, NHS 24 said.
It has also changed use - from an out of hours only to a 24/7 service, with members of the public now asked to call before visiting A&E.
While staff are working tirelessly, the increased demand and staffing pressures caused by Covid-19 or related self-isolation have meant some patients have had to wait for longer, said NHS 24’s Director of Service Delivery, Steph Phillips.
Patients calling with Covid-19 symptoms now account for up to a quarter of calls, she added.
Hundreds of extra staff have been recruited to deal with increased demands, and new office space has been acquired to allow for this.
In October 2021, more than 11,000 callers waited longer than an hour, compared to 391 in 2020, and none in 2019.
In the six months to November 2021, a total of 42,264 callers waited more than an hour, a 17-fold increase on the same period the year before.
Just under 450,000 calls have been unanswered since the beginning of 2021.
NHS 24 said calls may be unanswered because patients become frustrated at long wait times, but this also may be because they have been directed to other care pathways by the helpline’s pre-recorded message.
“As with the whole of the NHS across Scotland, demand for NHS 24 services has increased as a result of the Covid-19 pandemic,” said Ms Phillips.
She added: “The unprecedented growth in demand for the 111 service means that, at times, people have experienced a longer wait time for their calls to be answered.
“As with all NHS staff, people working at NHS 24 have worked tirelessly throughout the pandemic, with a commitment to deliver safe and effective services 24/7, and answer every call as quickly as possible.”
The Scottish Government said it has increased funding to NHS 24 by over £20 million this year for extra staff and another call centre in Dundee.
“We recognise that during the pandemic, some patients have experienced longer wait times than normal, due to increased demand during peak periods,” a spokesperson said.
They added: “While NHS 24 provides a highly effective and valuable service to patients across Scotland it is also a key part of our redesign of unscheduled care and people who feel they may need to attend A&E but it is not immediately life-threatening are asked to contact the service for an appointment to be arranged for them.
"This benefits both the patient and our health service and helps manage capacity within emergency departments.”