I’m going to use an analogy here which I think will answer this question:30-40 years ago, different gas stations had different additives in their gasoline. They would add different components to make their own “top tier” gasoline. Over time, the different companies would test the mixture of other companies gasoline additives, and find what worked and what didn’t.

Over the years, all of the different gas companies now basically have the same additives in their gas. Today, a typical gasoline mixture contains about 150 different additives including butane, pentane, isopentane and the BTEX compounds (benzene, ethylbenzene, toluene, and xylenes). Gasoline also contains lubricants, anti-rust agents and anti-icing agents to improve car performance.These days you can basically go to any gas station and get the pretty close to the same gasoline mixture, because all the companies copied each other to come up with the best mix.

Pharmacies do the same thing. There is not much in testosterone. There is the hormone, the ester, the carrier oil, and some benzoyl alcohol (for sterility). Some pharmacies also add things like DHEA to their mix. While they pretty much all have the same concentrations, there are subtle differences between pharmacies. You may react slightly differently to one over another, but the FDA regulates all injectable medications, so each pharmacy is audited at least once annually. You can trust that you are getting legitimate testosterone.