The decision to spend some time in a detoxification unit to withdraw from your drug of choice can be a frightening thought, whether it is your first time or your twentieth; whether you're going to rehab, to lower your tolerance, or just playing it out. Today detox units are staffed by doctors, nurses and other allied professionals and are safe environments.
On your arrival you will be assessed and asked about what you are using and the frequency, so it is important that you keep it pretty honest, especially if you are taking a cocktail of drugs. They can only act and plan your withdrawal on what you say, and the last thing you want is an unexpected seizure on your hands, so no matter how bad the war stories are tell them — they will listen. They may have heard a lot, but they haven't heard what you've been going through. It will give them and you a better understanding of what to expect.
One important thing that you may want to think about is that you are there for you and nobody else, so try not to run with the pack — it may end in tears with you being asked to leave. If you are thinking of using while in detox it is a bit selfish, it does impact on others, and the staff takes a grim view of such behavior. You will at times be bored, frustrated, and just plain pissed off with it all, so if you are thinking of leaving halfway through your withdrawal (and you will — it's not much fun being sick and hanging out) it might be best to have a yarn to the staff member that is assigned to you and tell them what is happening. It's not a good idea to shoot yourself in the foot by leaving as the process of re-admission is problematic to say the least and you may have to wait a few weeks. If you are homeless, it's not such a great idea.