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Understanding Injectable Steroid Esters

Which Testosterone Is the Best for You?

By William Llewellyn


One of the first things people usually take notice of when they start getting into steroids is the large variety of drugs actually out there. There are literally dozens of them. And perhaps even more perplexing at first glance is that there are numerous different types of the same steroid. Testosterone, for example, can be found as testosterone acetate, propionate, phenylpropionate, cypionate, enanthate, decanoate, undecanoate, hexylhydrobenzylcarbonate; the list goes on and on. You immediately wonder what all these different testosterone compounds are, and why we need so damn many of them. Let’s take a close look at a technology that has allowed us to create effective injectable forms of natural steroid hormones like testosterone: esterification. In the process, we can understand how and why these compounds work, as well as dispel quite a bit of the myth and misinformation that has unfortunately surrounded the subject in bodybuilding circles for decades.


The Ester: How It Works


Esters are fatty acids that are attached to steroid molecules in order to increase their therapeutic value when given by injection. Whenever you see a drug like testosterone cypionate, the cypionate part is the fatty acid that has been added to testosterone. This attachment increases the lipophilic (fat-soluble) nature of the steroid hormone, as well as its partition coefficient (a measure of how much the compound prefers to be in an oily environment as opposed to a watery one). Testosterone normally has a low level of solubility in oil, and a low partition coefficient. This allows it to be picked up so rapidly by the watery environment of the blood once it is injected, that it cannot offer much therapeutic value (it is in and out of the body too quickly).


Our esterified injectable steroids, however, are very different. The ester makes the steroid dissolve poorly in water, but well in oil. Essentially, it gives the steroid fat-like properties. This means after it’s injected, its low affinity to dissolve in water will cause it to take longer to be absorbed by the bloodstream. The injected deposit of steroid can sit dormant for days, even weeks, before the body is able to fully utilize it. This means fewer injections, steadier serum concentrations of hormone, and much greater therapeutic value. Esterification was clearly a tremendous breakthrough in medical research, and today remains the standard technology used with injectable steroid products.


Different Esters


There are dozens of different esters, probably hundreds if you count those that never made it into steroid products. A loose rule of thumb is, the longer the ester (its carbon chain), the slower acting the steroid will be. You can sort of look at it like this: The larger the ester is, the larger the percentage of fatty acid will be in your new (hormone + fatty acid) compound, and the more “fat-like” the new compound will be. Acetate, for example, is a short ester of only two carbon atoms and extends steroid release for only a couple of days. Its partition coefficient and oil solubility are fair, but not dramatic. (This is why you don’t see 200mg/ml trenbolone acetate products). Injections of acetate compounds need to be repeated two to three times a week in order to keep blood levels steady.


Decanoate, on the other hand, is a long-chain ester with 11 carbon atoms, and is capable of delivering its steroid to the blood over a period of three weeks or more. It has a high partition coefficient, and a high level of oil-solubility. It is so slow acting that weekly or even bi-weekly shots are sufficient for treatment. Phenylpropionate stands out as sort of an exception to this rule. It contains nine carbon atoms, but not in the classic straight chain you see with most esters. Its structure gives it a moderate level of oil-solubility and extends steroid release only for few days longer than acetate.


Each ester represents a different option with respect to how fast acting you want the steroid to be. But what does this really mean? It means that if you inject 100 milligrams of testosterone in the form of testosterone propionate, for example, you will get most of the 100 milligrams of hormone into your body within a few days. By the time you’ve had your third shot, maybe the middle of your second week, you already probably have had 200 milligrams of active testosterone in your body. You are likely to notice the anabolic effects of steroid therapy pretty quickly with a drug like this.


If you took the same 200 milligrams in the form of testosterone decanoate, you’d still be waiting for quite a bit of steroid to be released at this point. Your cycle would be a little slower out of the gate, so to speak, and it may take an extra week or so for results to really “kick in.” But after a few shots, the difference between release intervals becomes irrelevant. You will ultimately be getting the same amount of testosterone into your body with either drug, so it is difficult to say any one type is truly better than another. Your cycle with Decanoate may start off a tad slower, but it will also last a tiny bit longer than your cycle with propionate. In the end, there’s no real difference.


Ester Size, Weight and Effect on Injection Frequency



No. Carbons

Frequency of Injection*

Percentage of Weight



2-3 days




3 days




1 week




1 week




4-5 days




10-12 days



*Efficacious dosing schedules commonly used for bodybuilding purposes. Figures may not reflect typical prescribed medical schedules. Weight value reflects how much of the new compound (such as testosterone propionate) is actually the ester (propionate) and not steroid (testosterone).



Inner Workings


It is vitally important to understand that once the esterified steroid is released into the bloodstream, enzymes will remove the ester to yield the active (free) steroid again. The compound is totally inactive until this happens, as the presence of the ester prevents androgen receptor binding. Your muscle cells will only see free active testosterone, not an esterified compound like testosterone propionate. The existence of so many different steroid esters has spawned quite a bit of theory and misinformation about these compounds among bodybuilders, who tend to not understand that the ester only controls steroid release, not activity.


Some incorrectly believe each form of testosterone has its own unique binding properties, or attribute large variances between compounds in regard to estrogen conversion. You are constantly hearing things like, “Take testosterone propionate during your cutting cycles, it will produce less water retention than enanthate or cypionate”; or “Sustanon is better because it hits four different steroid receptors, not one.” When you understand the mechanism in which esters work, however, you immediately see the flaw in this line of thinking. How can propionate possibly cause less estrogen conversion if it yields the same free steroid as enanthate? The free testosterone circulating in the blood doesn’t know, or care, how it got there, and behaves the same way testosterone always does. In order to make a less estrogenic steroid, we would have to change the testosterone molecule itself.


Sustained-Release Blends


Sustanon is probably the most sought-after testosterone product in the world. The fact that it contains a sustained-release blend of different esters has everything to do with this, of course. After all, it has four different kinds of testosterone in it, not one. People seem to be immediately drawn to it as some kind of super-testosterone. One company released a blend of seven esters of testosterone (called Equitest) on top of that, which promises to gather its own bit of attention on the black market – just about everything from acetate to decanoate is in it.


But are sustained-release blends like these really better? If you’re a bodybuilder taking supraphysiological doses of testosterone week after week, the answer is a resounding no. Drugs like Sustanon are great advances if you are a medical patient tied to a doctor’s office for testosterone-replacement injections. In such cases, you have to visit less often (perhaps once every three to four weeks), endure the discomfort of injection less frequently and maintain steadier concentrations between visits. But if you are going to inject the drug every week anyway, there is simply no advantage in it at all. At best, you might find the presence of short-acting esters like propionate and phenylpropionate will help with your over-anxiousness to start growing (the cycle may kick in a little sooner). But, ultimately, the cycle will turn out little differently than if you took testosterone enanthate every week.


Choosing the Right One


So you’re going to start shopping for your next cycle tomorrow, and are wondering which testosterone is the best one to purchase? The answer is none of them, and at the same time, all of them. What I mean is, if you do not care about how often you have to inject yourself, have no specific need for the fastest-acting compound, and find all the esters comfortable to use, then it should always be a simple math equation: How much testosterone am I getting for each dollar? Remember, you need to calculate the weight of the ester (see the chart) when figuring this out. For example, 100 milligrams of testosterone cypionate yields only 70 milligrams of free testosterone. This is compared to 87 milligrams with testosterone propionate. After all, it is the testosterone we are really after, not the fatty acid stuck to it.


In looking over prices list for a popular veterinary steroid supplier in Mexico, we can see how it is done. We’ll compare three different testosterone injectables from the Quality Vet line. All are in 10-milliliter vials, which makes the math a little easier. The QV enanthate product has 250 milligrams per milliliter (mg/ml) of steroid, which equates to 1,800 milligrams of total testosterone in each vial, and sells for $44 (in Mexico, not here, so stop drooling). This comes to about 41 milligrams of testosterone per dollar.


Their testosterone propionate contains 100 mg/ml of steroid, which equates to 830 milligrams of testosterone in total, and sells for $25. This comes to 33 milligrams of testosterone per dollar. Lastly, their Sustanon clone contains 250 mg/ml of the requisite propionate, phenylpropionate, isocaproate and decanoate blend, which equates to about 1,720 milligrams of total testosterone (172mg/ml, a figure you might want to remember) and sells for $85. This adds up to only around 20 milligrams of testosterone per dollar. A little math like this makes me wonder why the hell people love Sustanon so much. I’d go with enanthate every time, and get about twice as much testosterone for my money.


William Llewellyn is widely regarded as one of the world’s foremost authorities on the use of performance-enhancing substances. He is the author of the bestselling anabolic steroid reference guide ANABOLICS and CEO of Molecular Nutrition. William is an accomplished researcher/developer in the field of anabolic substances, and is also a longtime advocate for harm reduction and legislative change. He built the website, an extensive online database of information on anabolic steroids and other performance-enhancing drugs.




Biological half-lives of [4-14C]testosterone and some of its esters after injection into the rat. KC James, PJ Nicholls and M Roberts. J Pharm Pharmacol1969; v21 p24-27.


Implications of basic pharmacology in the therapy with esters of nandrolone. J Vies. Acta Endocrinol 1985; (Supp 271) 38-43.


Pharmacokinetics and Pharmacodynamics of Nandrolone Esters in Oil Vehicle: Effects of Ester, Injection Site and Injection Volume. Minto, Howe et al. J Pharmacol Exp Ther 281(1) 93-102.







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