Any GP in Ireland can take a blood test and send it to the local public hospital for testing.The testing is free but the GP is entitled to charge for taking the bloods and transporting them to the hospital.
If you are having this done monthly, it's worth finding s GP with reasonable charges.
The invoice from the GP will be a normal GP invoice so can be claimed on health insurance if you have a policy which covers GP visits.
Any charges which are not covered by insurance can be used to claim tax back at 20%.
Alternatively, you can go to the phlebotomy department of the hospital and have it taken for free. However, the hours they are open may not suit your working hours.