Different testosterone esters are often blended into one injectable preparation. In some cases up to seven esters are used, but the most popular formulation is that of Sustanon 250 where four esters are mixed together. This is done to take advantage of the faster acting esters while still only requiring weekly or bi-weekly injections. It is often believed to be a superior form of testosterone, but in reality it’s nothing more than just testosterone. One drawback of testosterone blends are that they incorporate esters with long carbon chains and those chains occupy allot of molecular weight, so the actual dosage of hormone is less than one would obtain from shorter esters like propionate. Testosterone blends are most useful during bulking phases where frequent injections are not possible.
The preservative benzyl alcohol has been associated with serious adverse events, including the "gasping syndrome", and death in pediatric patients. Although normal therapeutic doses of this product ordinarily deliver amounts of benzyl alcohol that are substantially lower than those reported in association with the "gasping syndrome", the minimum amount of benzyl alcohol at which toxicity may occur is not known. The risk of benzyl alcohol toxicity depends on the quantity administered and the liver and kidneys’ capacity to detoxify the chemical. Premature and low-birth weight infants may be more likely to develop toxicity.
Injectable steroids are injected into muscle tissue, not into the veins. They are slowly released from the muscles into the rest of the body, and may be detectable for months after last use. Injectable steroids can be oil-based or water-based. Injectable anabolic steroids which are oil-based have longer half-life than water-based steroids. Both steroid types have much longer half-lives than oral anabolic steroids. And this is proving to be a drawback for injectables as they have high probability of being detected in drug screening since their clearance times tend to be longer than orals. Athletes resolve this problem by using injectable testosterone early in the cycle then switch to orals when approaching the end of the cycle and drug testing is imminent.