Hi Vince. My name is Jasen and I have worked in a compounding pharmacy and have worked with compounders for roughly 8 years. Most manufactured testosterone injectables are suspended in cottonseed or sometimes sesame seed oil. Both of these oils are sterilized and pass USP standards, but they are indeed "cheaper" oils typically used in mass-produced testosterone. Compounding pharmacies can use any oil you and your physician requests, like grapeseed and sesame oils. The amount of the oil injected should not be a concern as it is such as small amount, which the body will metabolize, and it is sterilized of impurities. Unless you are allergic to the oil itself than I would not be concerned at all. If you are allergic to cottonseed than you will want to choose another oil to avoid a reaction.
Although you did not ask about the difference between testosterone enanthate and cypionate, here is a link which discusses the different testosterone esters: http://defymedical.com/resources/health-articles/187-common-injectable-testosterone-esters
Although you did not ask about the difference between testosterone enanthate and cypionate, here is a link which discusses the different testosterone esters: http://defymedical.com/resources/health-articles/187-common-injectable-testosterone-esters
