Human Chorionic Gonadrotropin

HCG is provided as a glycoprotein powder to be diluted with water, and acts in the body like LH, stimulating the testes to produce testosterone even when natural LH is not present or is deficient. It therefore is useful for maintaining testosterone production and/or testicle size during a steroid cycle. Use of this drug in the taper is rather counterproductive, since the resulting increased testosterone production is itself inhibitory to the hypothalamus and pituitary, delaying recovery. Thus, if this drug is used, it is preferably used during the cycle itself. A daily amount of 500 IU is generally sufficient, and in my opinion usage should not exceed 1000 IU per day.
Daily administration is superior to less frequent administration.

Doses over 1000 IU are noted for their tendency to cause or aggravate gynecomastia, and also act to desensitize the testicles to LH.

HCG may be injected intramuscularly, subcutaneously, or in a shallow injection about 1/4" deep with the needle going straight in. A 29 gauge insulin needle is recommended.  Injection speed should be slow.

Some HCG products are diluted 5000 or even 10,000 IU per mL, while others are diluted 1000 IU per mL. So far as I know there is no need to make the preparation so dilute. Once mixed, the preparation should be refrigerated and used within a few weeks. The substance is also somewhat temperature sensitive before mixing and should not be exposed to excessive heat.

HCG does not correct the problem of progressively-decreasing ejaculatory volume that is typical during a steroid cycle. So far as I know the only cure is to go off-cycle and use Clomid, but it is possible that HMG, a related drug which works analogously to FSH  might be useful during a cycle to treat this problem. HMG supports spermatogenesis and is commonly used in conjunction with HCG to treat male fertility problems. (Consider use of HMG to maintain ejaculatory volume to be a strictly past-the-cutting-edge hypothesis: I have not yet had the opportunity to test the matter.)

The athlete who would otherwise fail a urinary ratio test because of low epitestosterone may find HCG useful in increasing epitestosterone and therefore improving this ratio. A 500 IU dose is sufficient, but on the other hand, HCG itself is also banned by the IOC and is readily detected in urine.

HCG can also useful for returning testosterone to normal levels should levels be low post-cycle, or, with care, to increase levels from normal to high normal.  Titration of the dose, by measuring T levels and then adjusting the HCG dose accordingly, is recommended for long term use.