Adhering to the full treatment regime appears to significantly increase the chances of a clearing the virus. This is as true of the new Direct Acting Anti-viral pills (DAAs) as of interferon and ribavirin.
Adherence to treatment is particularly important with DAAs because they appear to be able to cause resistance in some cases. Because hepatitis C mutates a lot, your virus is in fact a collection of millions of slightly different viruses. Some of these viruses may be more resistant to the drugs, meaning the drugs find it difficult to work against them. What the drugs do is stop the viruses making new copies of themselves. If you keep missing doses, the viruses, especially those that are resistant will be able to continue to replicate when the drugs are not acting. This will mean your chances of getting rid of them is reduced but, worse, you will find that you have many more of the resistant viruses at the end of treatment than at the beginning. This could mean that future treatments don’t work so well.
It is therefore very important not to give yourself a few days off the treatment, perhaps because you don’t feel well and to do everything possible to ensure you don’t forget doses. It is worth being as well prepared as possible before the treatment begins and well supported during it.