The Health Service Executive has said that the National Hepatitis C Treatment Programme must operate within its budget this year of €30 million.
It has put a hold on new patients starting treatment which can cure people of the virus.
The executive said an unprecedented volume of patients were started on the treatment during May and June.
An anti-viral tablet can treat the virus and can cure most patients.
Currently, around 500 patients are at different stages of treatment around the country.
The programme was set up in 2015 and so far 2,000 patients have started treatment, with the most serious cases treated first.
All those who were infected with hepatitis C through contaminated blood and blood products have now been offered treatment with cure rates as high as 97%.
Hepatitis C is a contagious virus that affects the liver and can only be contracted through contact with infected blood.
The executive said that a "realignment" of the programme will be concluded in the next two weeks and new patients prioritised by their clinicians will then start treatment.
Up to 30,000 people in Ireland will require treatment in the coming years.
The aim of the national programme is to provide everyone in Ireland infected with the virus with access to treatment and to make hepatitis C a rare disease by 2026.