The number of calls taken by NHS 24 broke the 1.5 million mark last year
Bosses at NHS 24 have been ordered to provide a progress report by November on efforts to cut staff sickness absence levels.
The deadline was set by Health Secretary Nicola Sturgeon, who chaired the annual review meeting of the health telephone advice service on Tuesday.
In December, bosses were told to come up with plans for cutting sickness absence levels to 6% by next March.
Lib Dem health spokesman Ross Finnie called for a review of 24-hour care.
New figures showed that sickness absence levels were running at levels of between 7.88% and 8.59% over the past year.
But recent monthly levels have shown an improvement, with figures of 6.12% in May and 5.97% in June.
NHS 24 chairman Allan Watson told the meeting: "Although this does represent good progress against the 6% target, we do recognise there will be seasonal variation and continuing challenges if we are to be able to sustain this improvement."
He said 90% of the helpline's services were delivered in the out-of-hours period, with the "inevitable" anti-social working that this entailed.
Ms Sturgeon said: "We will be looking for a report by November this year on how you are performing against projections and your confidence in meeting the target."
Mr Finnie said the absence rate at NHS 24 was the highest of any health board and was "entirely unacceptable".
He added: "Despite being given an easier target than other health boards to cut staff sickness, NHS 24 failed to achieve it.
"It is simply not good enough for the health secretary to order a progress report into NHS 24's efforts to cut staff sickness.
"It is time for a review of the provision of 24-hour care in Scotland and it should begin urgently."
The annual review heard that 90% of urgent calls got a response within 20 minutes.
It was also revealed that the total number of calls taken by NHS 24 last year broke the 1.5 million mark for the first time.
Some calls came from overseas - including one from a Scots couple on honeymoon in Thailand, after the bride was bitten as she posed for a photograph with a monkey on her shoulder.