HCG or Human chorionic gonadotropin, which is derived from the urine of pregnant women, is an injectable drug  for the treatment for undecended testicles in young boys and as a fertility drug used in aid of inducing ovulation in women.

HCG basically "acts" as Leutenizing Hormone (LH) in your body. LH is a Gonadotropin. They were first extracted from the human in 1958; more precisely the pituitary glands. A gonadotropin is any substance that stimulates the gonads (ovary, testes). It is heterodimeric (initiates prophase of mitosis) with an alpha subunit identical to LH (luteinizing hormone), FSH (follicle stimulating hormone) and TSH (thyroid stimulating hormone). LH is as stated above is called a gonadotropin because it stimulates the gonads (testes). It is produced in the pituitary cells and is made up of a beta chain of 115 amino acids and an alpha chain of 89 amino acids. In the testes, the LH binds to receptors on the leydig cells which in turn stimulate the synthesis and secretion of testosterone.
Among athletes, HCG is used to stimulate natural Testosterone production during or after a steroid cycle, which has caused natural levels to be reduced, often stacked with an antiestrogen for even better results. Stopping a steroid cycle abruptly, especially when endogenous androgens are absent, can cause a rapid loss in the athletes newly acquired muscle. When HCG is used to stimulate natural production, a notably pronounced crash will be avoided. HCG is always packaged in two separate vials, one with a powder and the other with a sterile solvent. These vials need to be mixed before injecting, any left needs to be refrigerated, and has a life span of about 10 weeks.
Your best bet is to start at 250iu or 500iu each day for 5 or 6 days, and if you don´t notice anything happening (nuts dropping and getting bigger) up the dose slightly. Small doses like 500iu two days a week isn´t going to cut it like some people think. The only thing small doses of HCG may be useful (sublingually) for is reducing symptoms of benign prostatic hyperplasia (7). Yeah, that´s right, you can probably reduce some symptoms of an enlarged prostate with the use of small doses of HCG.
Most users cycle HCG near the end of a steroid cycle, you should start your HCG therapy on the last week of your cycle. For best results you should also run nolva while you run HCG as taking HCG by itself will do little to nothing and gyno even though rare may also flair up. Once the HCG cycle is finished you continue with your usual clomid or nolvadex (preferably the latter) for pct(post cycle therapy) as it is more effective when used in conjunction HCG for pct. With an AAS cycle of 6 to 10 weeks HCG may not be necessary unless extreme doses of AAS were used or there is an existing problem of testicular atrophy or you are running a heavy oral only cycle. AAS cycles of 12 or more weeks should have HCG as a part of post cycle plan.
HCG by Global is offered here by us in a 5000 iu vial with 1 Solvent vial. Please note that sometimes we send an alternative HCG by another manufacturer but quality is same or better.