I was prescribed testosterone cypionate for injection, one shot every 7 days. The shot size is 1ml for delivery of 100mg of testosterone. Naturally, when I found out my prescription, I did some research to figure out what I'd be injecting into my body.
Most testosterone prescribed for testosterone replacement therapy is in the form of a testosterone ester. Esterification is done to improve the solubility of testosterone in oil, which in turn slows the release of the testosterone once it's injected into the body. Testosterone comes in numerous types of injectable esters, including the common testosterone enanthate and testosterone cypionate, as well as the less common esters caproate, propionate, acetate, phenylpropionate, isocaproate, decanoate, and undecanoate. Each of these esters is a molecular chain composed of carbon, hydrogen, and oxygen atoms, the difference being how many carbon and hydrogen atoms make up the chain.
Once an ester group has been added, testosterone becomes more soluble in oil, but less soluable in water. It's also interesting to note that, in general, the more carbon atoms an ester has, the more oil-soluble it becomes. Testosterone propionate, for example, has 3 carbon atoms in the ester group and is less soluble than testosterone cypionate which has 8. The ratio between oil and water solubility is called the "partition coefficient". The higher the oil solubility, the higher the partition coefficient. As far as oils goes, testosterone compounds usually use cottonseed or sesame seed oil.
The partition coefficient is important because it indicates how quickly the testosterone is released into and stays in your system. Generally, the quicker the release, the shorter the stay. If the testosterone is released too quickly, testosterone rises quickly, but then soon starts declining once the dose has been used. So a testosterone solution with a very low partition coefficient is immediately available and used up quickly once it's injected, while a solution with a higher coefficient is released more slowly and lasts longer.
Testosterone cypionate is an example of a slow-acting compound with a high partition coefficient. When injected, the compound slowly dissolves, resulting in a slower release of testosterone with more stable, longer-lasting testosterone levels.
For testosterone replacement therapy, slow-acting compounds are usually prescribed, since a slower releasing compound means fewer injections and more constant testosterone levels. Testosterone enanthate, which has 7 carbons in the ester, and testosterone cypionate, which has 8 carbons, both take around 8-10 days to be fully released. As such, these testosterone esters are usually injected once every 1 to 2 weeks. In contrast, testosterone propionate with only 3 carbons in the ester, is fully released in 3-4 days. Using testosterone propionate would mean smaller doses injected more frequently.
So from the above, you can see that the dosage and frequency of shots depends a good deal on which testosterone ester is prescribed. Testosterone dosages range from 50mg to 300mg per injection, depending on the ester and dosing schedule. A typical dosing schedule might be 200-250mg every 2 weeks, or 100mg every week to 10 days. Blood levels should be monitored and the dosages adjusted according to an individual's response.
My Prescription
The clinic I went to prescribed a 1ml testosterone cypionate once weekly, with each ml containing 100mg of testosterone. I do the injections for a month, then get my levels checked, with adjustments (if required) made according to my individual results.
Below is some more information on the individual testosterone esters:
Testosterone enanthate is one of the two most commonly prescribed testosterone esters in the United States. It's slow-acting with a release time of 8 - 10 days. Testosterone enanthate is usually injected between once a week to once every three weeks.
Testosterone cypionate is the other most common injectable form of testosterone prescribed in the United States. It's also slow-acting, with a release time of 8-10 days. Testosterone cypionate injection schedules run from once every week to once every three weeks.
Sustanon is the brand name for two formulas of injectable testosterone that contain an ester blend. Sustanon 100 contains three testosterone esters: testosterone propionate, testosterone phenylpropionate, and testosterone isocaproate. Sustanon 250 contains four testosterone esters: testosterone propionate, testosterone phenylpropionate, testosterone isocaproate, and testosterone decanoate. Both formulas feature both fast-acting and slow-acting esters, and are typically injected once every week to once every four weeks.
Testosterone propionate is a fast-acting ester with a release time of 3-4 days. To keep blood levels stable, propionate is usually injected one to three times a week.
Testosterone phenylpropionate is a slow-acting ester with a release time of 1-3 weeks. Testosterone phenylpropionate is one of the components of Sustanon and Omnadren.
Omnadren is the brand name for a blend of four testosterone esters: testosterone propionate, testosterone phenylpropionate, testosterone isocaproate, and testosterone decanoate. It is pretty much the blend as Sustanon, featuring both fast-acting and slow-acting esters. It's injected from once every week to once every four weeks.
Injectable aqueous (water based) testosterone is available, but it is very short-acting, being completely released in the system within hours. It's not used for replacement therapy, since it would need to be re-injected multiple times daily to maintain stable blood levels.
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