Is it bad to start hcg diet while already on a diet pill?

Plain and simple, the HCG diet program is a SCAM. It's a 30X homeopathic product. That 30X means there is one part of HCG in 1 x 10^30 parts of water. Yes, that's a 1 with 30 zeros after it. Some products are as dilute as 60X, a 1 with 60 zeros after it.

You lose weight because of an anorexic diet, you're limited to 500 calories a day. THAT'S how you lose the weight, not by taking drops of water mixed into a glass of water or under your tongue.

Just so you know 10^30 drops of water equate to over 16 TRILLION cubic miles of water. In all those cubic miles of water, there would be just 1 drop of HCG.