Cypionate injections actually had a very lackluster history in its early years and it is very important for any man interested in injections to understand why. In fact, it’s not an overstatement to say that many men have had quite miserable experiences, but in the great majority of cases, you can’t blame cypionate! Blame the docs who usually just did not know any better. Let me give you some examples from the Peak Testosterone Forum:
NOTE: For reasons unknown, in some countries testosterone enanthate is used almost exclusively over testosterone cypionate. The two have similar half lives and virtually everything on this page that applies to cypionate also applies to enanthate as well.
1. Time Between Injections. Ten or even five years ago, most doctors made the patient wait a ridiculous amount of time between injections – between two and four weeks in some cases! Here are some examples of the suffering this can incur:
The problem is that testosterone cypionate has a half-life of 8-12 days! So, after a couple of weeks, you have very little in your system. Notice that this man said that he felt terrible for two-and-a-half weeks, which of course corresponds to the time period when he had very little testosterone left. Basically, the doc gave him just enough testosterone to tease him!
Now most doctors do not do monthly schedules, but I get men all the time writing in via email or on the forum on two and three week regimens. These are little better. Even a two week regimen leaves a man hypogonadal for a few days at the end of the cycle. Just when life seems good, the rug gets pulled out from under you.
2. Roller Coster Rides. Men on cypionate injections every two or three weeks usually have other issues. The docs know that the patient is going to be low for the last week or two and so the tendency is to give more testosterone. The thinking is basically to give a big initial dose knowing that the man will go close to zero so that the average is in a more “reasonable” zone.
Elevated estradiol can also lead to some of the symptoms that are associated with HRT, such as fluid retention and prostate enlargement. For example, check out this poor guy whose doctor put him on a four week cycle:
“This progressed (after the first T injection) into heavier swelling, fatigue and bouts of shortness of breath along with several instances of dizziness leaving me in a position that I have now been out of work for nearly a month.” 
Again, it is likely his physician gave him a massive dose to try to compensate for the very long time between injections.
3. Unmanaged Estradiol. Something related to #2 is the fact that some men are overweight and some are “high converters,” meaning that they will change a lot of their precious testosterone into estradiol and end up with overly high estradiol levels while on testosterone replacement. Because of this, many HRT docs and anti-aging clinics try not to allow estradiol levels go too high or too low and generally keep men in the 20-30 pg/ml range for not only heart health but also to make sure that libido and mood do not crash as well. (See my Estrogen (Estradiol) Links for Men for more information.)
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One more important point: some men seem very sensitive to estradiol. A matter of just 3-5 points can help or hurt erectile strength and morning erections according to many reports. This may seem like a placebo effect, but keep in mind that a healthy male has a very high ratio of testosterone-to-estradiol and so a small amount of estrogen must be matches by a lot of testosterone to make up for it.
Besides erectile and libido issues, men going too high with estradiol can be at risk for “water retention”, i.e. swelling of the feet, etc. This can be frightening but is generally from estradiol going too high. In fact, look at the post above where the man experienced swelling from HRT.
High estrogen can also lead to mood swings, depression and other related brain-related issues. And it can be downright dangerous to the ol’ bod long term: one study showed that going over 37 pg/ml led to a 133% increase in mortality.  Some believe estrogens are the prime cause of prostate cancer. More on this below.
NOTE: There are three estrogens (estrone or E1, estradiol or E2 and estriol or E3). E2 is known as the “bad estrogen”, although a man needs to have sufficient estradiol for bone, brain and arterial health.
2, Arimidex. Many men on the forum are on Arimidex (anastrozole) and it is fairly common in any testosterone cypionate protocol. The reasons are that usually men are going to 900 to even 1200 ng/dl peak generally with cypionate and have put on weight over the years. This means that most men will end up with high estradiol levels for about a week.
Of course, talk to your doctor, but cypionate usually peaks on the 3rd of 4th day after the injection and so the first dose of Armidex will be given then (on a weekly cycle) with a second dose three days later. Common dosages are 1/4 mg or a 1/2 mg two times per week. From what I have seen, most of the anti-aging physicians and HRT clinics try to keep a man between about 20-30 pg/ml. Most men can get off of Armidex by losing weight, decreasing their dosage a little and going to more frequent injections. Arimidex is considered pretty safe and side effects seem to be low, especially in the lower dosages given for HRT. However, there is potentially the danger of knocking your estradiol too low and ending up with long term bone loss. I recommend scanning through these concerns on my site as well: Arimidex Problems.
NOTE: Although not very common, Arimidex can be given by itself to (most low T) men to raise testosterone levels as I document in my link on Testosterone and Arimidex . This is called by some Arimidex Monotherapy. Many men like the idea of simultaneously raising testosterone and lowering estrogen. See also my link on the Testosterone-to-Estrogen Ratio. I don’t think I have seen a case of Armidex Monotherapy on the Peak Testosterone Forum, although some men have asked about it.
3. Injection Options. There are several basic options here: you can go to the physicians office for injections; you can self-inject; or you can get a family member to give you the injections. Now not all doctors will allow injections outside of their office. The argument is that testosterone is a controlled substance. I think the real reason is to get you in for an additional office visit reimbursement or payment. However, on the forum, many men are self-injecting and I expect this percentage to increase over time.
The amount of fluid injected is relatively small and usually feels like a little ant bite. It is possible to “hit a nerve” which stings a little more and can leave a small sore bump for a day. But cypionate injections rarely cause issues if reasonable hygiene and procedures are followed.
NOTE: Yet another option out there is called “SubQ”. Standard injections are intramuscular, but for details on this other methodology, you can watch this training video by Dr. John Crisler, one of the most well-known online HRT docs that has been doing these sorts of things forever. According to Dr. Crisler, this has the advantages of 1) not poking so many holes in the muscle, 2) even more smoothing of testosterone and estradiol and 3) often reducing the need for Arimidex.
4. Needle Size, Length and Gauge. Your doctor should have very specific instructions for you on how to self-inject if that is route and you and he/she decide to take. But here are a few things to discuss and/or be informed of: 
a) The smaller the gauge number, the wider the needle. Thus a 20 gauge needle is bigger than a 21.
b) You will typically be given two needles, one to draw and one to inject. The larger is usually to draw.
c) Needle size can vary considerably. 18-22 is common for drawing and 21-27 for injecting from what I have seen.
d) You can inject with a 27 gauge needle, but it is much slower.
e) You also have varying needle lengths. 1.5 inch is very common, but your doctor may provide a slightly different length based on your body fat levels.
f) You may be able to use a 25 gauge needle (for intramuscular quad injections) if you can use a 1 inch needle. If you’ve got some extra fat and need a 1 1/2 inch needle that may be too challenging. 
The above applies to intramuscular injections. SubQ injections use a much smaller needle and it is a one step process.
5. To HCG or not to HCG. One very common protocol with the HRT clinics and anti-aging doctors is called “The Trifecta” and includes testosterone cypionate, Armidex and HCG. Short term results are pretty good but in my opinion you should avoid if at all possible the use of Arimidex. It is better to lose weight and lower your cypionate dose instead. HCG is added primarily to reduce testicular shrinkage and, in some men, provide a modest boost in libido and/or mood. See my link on Testosterone and HCG for additional details.
CAUTION: This page is NOT intended to be a guide for self-treatment. Always work with a physician, who can give you proper dosing/procedures as well as careful monitoring of estradiol, red blood cell counts, liver function and PSA. Also, realize that testosterone cypionate, and standard HRT in general, will lower fertility. If you want to have kids, discuss possible alternative with your doctor, such as Clomid and HCG Monotherapy .