HCG had become a significant play in the testosterone therapy world and with good reason: it keeps a man from losing testicular volume when on standard HRT (TRT) and be used by itself as HCG Monotherapy to maintain testicular function. Although HCG is a leutinizing hormone (LH) "mimic" and thus bypasses the pituitary and hypothalamuas, it at least keeps your testes in the game. In addition, HCG can preserve one's fertility, both as a monotherapy and even with HRT in many cases. So for men still trying to have kids, it's a nice option. (Sometimes HMG has to be added in as well. See my page on HCG Monotherapy for more deetails.) As of this writing, a Peak Testosterone Forum Poll showed that over 10% of the men on any kind of HRT were on an HCG Monotherapy program.
So one obvious question is dosage for all these uses of HCG. (Sorry ladies - I am only talking about dosages for men here.) Unfortunately, I see HUGE variability in dosing on the Peak Testosterone Forum. Keep in mind that probably 95% of the men on the forum are under a doctor's care, so there is a big difference in opinion among docs about how much HCG should be given. Let's look at the basic ways that HCG is currently being used by men and some common dosages. (Always discuss safety with your doctor. I'm just letting you know what I am seeing "on the street.")
CAUTION: I would argue against some of the higher doses of HCG, especially for older men, due to the fact that HCG is highly stimulatory and has a much longer half life than it's analog LH (luteinizing hormone). You can read about my reasoning in my page The Potential Dangers of Too Much HCG?
1. HCG Monotherapy. Dosages on this are all over the map. Let me give just some of the examples that I have seen recently:
a) 250 IU Every other Day. This low dosage (for monotherapy) boosted one of our regulars (electrify) up to a T level of 460 ng/dl. Most guys seem to target testosterone levels higher than this. However, his estradiol apparently shot up a bit more and he was even taking some Arimidex, an aromatase inhibitor that lowers estradiol. levels.
b) 500 IU Three Times Per Week (Dr. Shippen). One of the "HRT doctors" that I have the most respect for is Dr. Shippen. He is known for being thorough and also showing great concern for the long term health of his patients. One of our forum members wrote the following:
"Actually, the starting dose is 500iu 3x/wk. In fact, he wrote that on a prescription slip when he corresponded with me initially. The text of his HCG challenge then states basically that mid-level responders can go up in dosage accordingly. He is reasonable with this and conservative, thus, the idea is to go up just enough to get to a good testosterone level. Of course, if someone responded well to such a low dose such as 250, that could be a workable dose." 
Of course, you need to call Dr. Shippen's office to find the official version. (I have no affiliation.)
c) 700 IU Three Times Per Week. One of our senior forum members was on HCG Monotherapy for awhile and Dr. Shippen reportedly put him on 700 IU three times a week. He described his experience as follows:
"HCG use, I've been all over the map with dosages. I initially saw a very well renowned urology practice with a national reputation. They had the brilliant idea of prescribing the massive dose of 1,500iu/3x/week. Even back then I knew about HCG dosages and only did this for a week or so before I lowered it on my own. I then saw Dr Shippen, and he continued me on his own compounded brand of HCG at doses he wanted me to titrate (starting at 700iu/3x/week)." 
Notice that he and apparently Dr. Shippen considered the 1,500 IU to be too high of a dose and cut it back to 700 IU. Yet another member wrote that Dr. Shippen likes 500-700 IU per week and rarely if ever over that. This same member (JustAskin) stated that, when he went over 500 IU three times per week, his testosterone would actually drop. This supports the theory that an overly high HCG dosage can actually desensitize receptors or downgrade the Leydig cells themselves somehow.
d) 1000-2000 IU 2-3 Times Per Week. Quite a few experts warn against going too high with HCG as they feel it can lead to desensitization or perhaps even actual damage of the Leydig cells. However, it is a controverial topic as I'll show below and I have the subject argued both ways. For example, there are some endocrinological guidelines that recommend 1,000 - 2,000 IU 2 -3 times per week. This is a massive dose from what I have read, but I have seen guys on the forum doing this much.
"I just visited a hormone replacement clinic, and upon conversation I am trying HCG with arimidex. Doctor said that he starts people with 1,000 IUs two to three times a week. This is based on a 2002 American Association of Clinical Endocrinologists Medical Guidelines for Clinical Practice for the Evaluation And Treatment of Hypogonadism in Adult Male Patients. In this document in the section on Gonadotropin Therapy for Induction of Spermatogenesis they actually recommend 1000 to 2000 IUs two to three times a week. I also know that Dr. Crisler recommends no more than 500 IUs on a single day for the danger of desensitizing lh receptors. I told this to doctor and we agreed to start with 500 IUs per shot twice a week. Is that reasonable/normal?." 
However, if you read the actual paper, it may be indicating that this is not intended as a long term protocol and calls it an "initial regimen:"
The actual quote form the paper he cited was "It is known that HCG binds to leydig cell LH receptors and stimulates the production of testosterone. Peripubertal boys with hypogonadotropic hypogonadism and delayed puberty can be treated with hCG instead of testosterone to induce pubertal development. The initial regimen of hCG is usually 1,000 to 2,000 IU administered intramuscularly two to three times a week." 
HIGH DOSES OF HCG GREATLY RAISE ESTRADIOL LEVELS: Does this mean that this high doses are safe? Well, that's one you'll to discuss with your doctor, but personally I don't think so. And it's somewhat of a moot point, because going over about 700 or 1000 IU really sends the estradiol skyrocketing generally. For example, look at the story of this man:
"I took 16 2000iu hcg injections a few years back. I believe it was every other day injections into my ass cheek (I say this because next time I am going to do sub q into my stomach) - my test levels rose to 800s - my strength in the gym shot WAY up (my bench press max doubled within a week and I was able to see my abs) - it did NOT improve my sex drive at all though - I believe hcg converts into estradiol at a high rate so any chance at having increased sex drive was removed.." 
SUMMARY: The most common and cautious dosages on the forum seem to be 500-1,000 IU three times per week. HCG seems to stimulate estradiol levels more than standard HRT and thus might be a good option for men with low estradiol. However, for those with normal aromatase conversion, these higher estradiol levels often cause somewhat reduced libido and less than spectacular results when compared with standard HRT. Furthermore, Arimidex seems to be of limited value and libido is often, therefore, not raised as much on HCG Monotherapy. Advantages include better fertility parameters (generally) and increased testicular volume (generally).
CAUTION: Some men are concerned that long term use of HCG will atrophy the pituitary. This is because HCG bypasses the pituitary and jumpstarts the testes directly. Studies are lacking, so discuss with your doctor.
2. HCG with Intramuscular Weekly Testosterone Cypionate. One very common practice at HRT clinics and with anti-aging physicians is to simultaneously adminster HRT (testosterone therapy) and low dose HCG. This is done most often with testosterone cypionate injections. For example, when I was at an HRT clinic, I was taking between 120 and 150 mg of cypionate once per week and 250 IU of HCG twice per week. The timing of the HCG injections was meant to be at the low point, or trough days, and so I injected 250 IU on the day before my cypionate injection and 250 IU the day of.
Their are several common reasons for adding low doseHCG to one's HRT regimen, which I have outlined below.
NOTE: Some men need to go up to 500 IU twice per week to experience any increase in testicular volume.
1) AACE Hypogonadism Guidelines, Endocr Pract. 2002;8(No. 6) 451, "AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS MEDICAL GUIDELINES FOR CLINICAL PRACTICE FOR THE EVALUATION AND TREATMENT OF HYPOGONADISM IN ADULT MALE PATIENTS 2002 UPDATE"