HCG drops are most commonly considered "homeopathic" and are not true hCG. The theory in which they are to work, as is homeopathy in general, is that the true ingredient has been diluted to the point that, while there is actually very little if any actual ingredient in the solution, the "energy" of the ingredient is maintained and even maximized and is just as effective.
While there is potential truth to energy healing, there is no scientific evidence or biochemical data to support it.
In my professional and medical opinion, low calorie diets should NOT be enforced without actual medical grade hCG, proper biochemical testing, and comprehensive medical guidance.
In total, drops should NOT be used alone as low calorie diets which cause starvation, catabolism, the loss of muscle and bone, and the further slowing of the metabolism and thyroid gland.