There has been some controversy as to whether or not HCG is safe to use for weight loss. It is important to keep in mind that the dose used is much lower than the levels of HCG that mother and fetus are exposed to during pregnancy.
Most people report that they experienced no side-effects at all when using HCG. For those people who did experience side-effects, these included fatigue, headaches and hunger. These may have been a result of the calorie restrictions rather than the actual HCG injections. Headaches are a common symptom of the body detoxing from caffeine and sugar so if you are reducing foods and beverages containing caffeine and sugar, you may experience fatigue and headaches initially. In most cases, your body will adjust after an initial period of detox.
When compared to other much more invasive and extreme methods of weight control such as lap-band surgery, the risks associated with HCG may not seem so high. It may also be interesting to note that HCG has been associated with a reduced risk of breast cancer (you can read the Fox News article about this here). Having said that, it is always a good idea to talk to your doctor about your specific situation before beginning any new medication or diet.