here you go, then, straight from the horse's mouth:
http://hcgdietinfo.com/hCG-Side-Effects.htm
hCG Side Effect: Ovarian hyper-stimulation syndrome
Some women on the hCG diet have developed a side effect known as ovarian hyper-stimulation syndrome (OHSS), especially during the first round of treatment. While OHSS is rare, it can be a life threatening condition, so call your healthcare provider right away if you experience any of the following symptoms: Severe pelvic pain; swelling of the hands or legs; stomach pain and swelling; shortness of breath; weight gain; diarrhea; nausea or vomiting; or urinating less than normal.
hCG Side Effect: Early puberty in young boys
Another potential side effect of hCG injections for weight loss is the cause of early puberty when used to treat young boys. So call your doctor if you see any of the following symptoms of early puberty: Deepened voice; pubic hair growth; increased acne; and increased sweating.
hCG Side Effect: Multiple Births in Pregnancy
Using HCG may increase a woman’s chances of having a multiple birth (twins, triplets, quadruplets, etc). A multiple pregnancy can be a high risk pregnancy for both mother and child, so consult your doctor for instructions if you are pregnant or may become pregnant.
hCG Side Effect: Common side effects of hCG injections for weight loss.
Other less serious side effects of hCG can include, but are not limited to: headache; feeling restless or irritable; mild swelling or water weight gain; depression; breast tenderness and swelling; and or injection site inflammation and pain.