The bitters do stimulate the gall bladder to produce more bile. I found the same thing when I first started on the bitters, I was using too much, I have cut down to just a 1/2 teaspoon on the back of the tongue morning and night. This appears to be the ideal dose for me. As Hv says , its not the amount that is important, just that it stimulates the vagus nerve at the back of the tongue, and you only need a small amount to do this.
The effect of the bitters on my digestion has been fantastic, so I probably will continue to use them indefinitly.