There are calls for the HSE to stop referring cancer patients' debt to collection agencies.
The Irish Cancer Society says the practice is causing distress and worry to those going through treatment.
The charity, which is today publishing advice on the issue, says they have received complaints from many patients.
Chief Executive of the Irish Cancer Society, Averil Power, said the sums sought can vary but the whole process is very unfair.
Ms Power said: "Ranging from just €80 in some cases up to €800 or more in others, so they are getting letters from debt -collecting agencies, threatening phone calls, threats that their name will be made public if they don't the fees.
"These letters are being sent to six patients who are dealing with the physical impact of their cancer, the emotional impact and all the other stresses with their family and the really can't cope with this stress, as well."
