I did this exact thing just over a year ago. I was not ready to cleanse and was being advised to do several liver flushes. I ended up very sick and very compromised, in pain, depressed and frustrated. At that time I was helped tremendously by an energy field worker, who helped me to stabilize and to feel good about myself.
Now I'm strong and flushing like crazy and everything is fine. Of course, this time I started cleasing very slowly and carefully. But the biggest difference was probably my emotional state and approaching the cleanses with a feeling of security and stability.
I wonder though, in a case where a person's health and/or life are in danger and cleansing is crucial. In this case it may be the best thing just to start.
I think it is only through trial and error that we learn what our body needs.