Spending on health is running €500m ahead of budget, General Secretary of the Department of Health Robert Watt has said.
He told the Oireachtas Joint Committee on Health that most of the figure is being spend on acute services, with "75% in the acute side".
Sinn Féin's David Cullinane suggested that it is "a racing certainty that we will have supplementary estimates in health".
"Yes, we will have a supplementary estimate by the end of the year," Mr Watt confirmed.
"Will it be close to a billion?" Mr Cullinane asked.
Mr Watt said that the department is doing all it can "to mitigate the challenges" while maintaining services.
This involves "managing this trade-off between very significant demands increasing, while we have a budget which is constrained".
Mr Cullinane said that the budget for this year was "grossly underestimated", and criticised the Government for adopting "a very poor way to fund a health service".
The 2,200 net increase in health service staffing this year will be a mix of new posts and safe staffing recruitments, Mr Watt confirmed.
Safe staffing involves recruiting extra personnel to deliver the same level of service in a sustainable way.
Mr Cullinane expressed surprise at this, as he thought that Minister for Health Stephen Donnelly had indicated that the increase was to consist entirely of new posts.
"I would have argued that safe staffing should have been separate. We were told 2,200 additional posts for new measures. Now it seems that some of it is safe staffing, so it's actually less than that," Mr Cullinane said.
"I think it's very unsatisfactory," he added.
Over half of consultants sign public-only contract
The committee also heard that more than half of hospital consultants have signed up to the new public contract.
As of 2 May, 2,229 consultants have signed up to the public-only contract, Health Service Executive Chief Operations Officer Damien McCallion said.
This is an increase of about 300 in the past two months, as the figure at the start of March was 1,923.
There are 4,258 consultants, Whole Time Equivalents (WTEs), working in the public health service, according to Government figures.
HSE Chief People Officer Anne Marie Hoey noted that 470 of those on the new consultant contract are new entrants since March of last year, with the balance being established consultants who switched contracts.
She said that, since the introduction of the new contract, the number of consultants applying for advertised positions in the public health service has doubled - increasing from two to four applicants for each post.
"We can see a huge increase in the interest - nationally and internationally - in positions here in what would have been hard to fill posts previously," Ms Hoey said.
Increase in out-patient appointments - HSE
The committee also heard that there were 4.2% more out-patient appointments delivered in the first quarter of 2024 as compared to 2023.
HSE Regional Executive Officer for the West North West Tony Canavan said that "thankfully the situation" at University Hospital Galway (UHG) "has improved slightly today relative to yesterday" when it was the second most overcrowded hospital in the country, after University Hospital Limerick.
However, he said that any patient having to wait on a trolley is a matter of "significant concern".
Mr Canavan also told the committee that there have been improvements at UHG over the past six months.
