FDA doesn't approve of using either HCG injections or diet drops for weight loss
,since you have to take a 500 calories with that and this is very dangerous as minimum a person requires is 800 calories.
HCG injections can cause confusion,dizziness ,headaches,abdominal pain
and other gastro intestinal problems.
Black stool could be an indication of gastro intestinal bleeding and so you must immediately get your stool tested to look for occult blood,although black stools can be caused by pepto bismol
Whether bleeding or not,you must immediately stop taking these injections as it may lead to severe electrolyte imbalance
and can cause cardiac arrythmias.Start taking proton pump
inhibitors like PANTOPROZOLE 40 mg daily .