The message above the forum did not always used to be there. Here's some personal experience with that recommendation.
By now, I've been thru dozens of liver flushes, two 10+ day master cleanses (several false starts under 3 days too!), and a few long Water Fasts in the last 4 years or so.
What I've noticed is that both Water Fasting and master cleanses I've done when I did the Liver Flush _prior_ to starting have been easy by comparison. By easy, I mean, less headachy, less achy, less exhausted, less yucky overall, in days 1-4 of the cleanse/fast. I have noticed this on a Water Fast as well. Those symptoms *always* go away on their own after day 4 of any cleanse I've done, and I start feeling quite fine by day 5.
The reason I'm posting now is that this is something I'm currently experiencing. I resolved to do a master cleanse starting Monday. I did a Liver Flush last Wednesday/Thursday, as it had been months since I'd done it last. I decided this time to try something different... to just take water until my blood Sugar dropped and my body indicated I needed calories, then start the lemon juice mix. I figured I'd use the opportunity to do a little communication with my body, to take in calories a little more consciously.
Almost three days later, that hasn't happened. I get a little sleepy in a warm room, or if I haven't gotten fresh air in a while, but that's about it. Frankly, I'm stunned. Water Fasts usually knock me on the butt for the 2nd-4th day. But I have noticed no suffering of any kind. So I'm gonna ride it out. But this is exactly what it was like doing the Master-Cleanse after a recent flush too. Really easy by comparison.
Based on that, I would not say that the flush is an absolute requirement, nor would I postpone your Master-Cleanse if that's what you're drawn to now. I've done it both ways and I'm only saying that I find it easier to get through the harder first few days of a cleanse
Please also keep in mind that there is no guarantee that my experience will be like yours or anybody else's. I had a lot of Liver Flushes under my belt before I noticed these things happening, so I may not the best person to describe what's going to happen to someone who's just starting. These forums are all about helping eachother make informed choices, but ultimately, you have to decide what's right for you.