When combination therapy is successful, it can improve the health of someone with HIV, making them less likely to develop what used to be called 'AIDS-defining conditions' and prolonging their life expectancy. In order for the anti-HIV drugs to be most effective a certain level has to be maintained in the body at all times. However, taking anti-HIV drugs can be complicated. Some people have take a large number of pills every day with restrictions about when they have to be taken and with dietary instructions which can make it very difficult to stick to. Some of the treatments have side effects as well.