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What Is An Ester?

Esters are molecular chains derived from carboxylic acids and are usually comprised of a hydrocarbon group (hydrogen and carbon atoms). Esters are usually coupled to the 17-beta hydroxyl group of the parent molecule and increase the active life of the steroid.

This alteration decreases the steroids water solubility (and conversely, increases oil solubility) meaning it isn’t as easily absorbed into the body’s circulatory system. Once injected, the steroid enters the muscle and then beings to slowly circulate around the body. The larger the molecular chain (the more atoms that are included in the chain), the more oil soluble the steroid is which increase the time it takes for the administered dosage to be released.

Once the steroid compound has begun to enter circulation, the body’s enzymes work to remove the ester, freeing the parent hormone so it can exert its activity. This takes a varying amount of time which depends on which ester the hormone is attached to.

Retarding the steroids release is extremely beneficial, as a free version of the hormone would not remain active nor exert its effect for long (typically hours) and frequent administration would be required in order to see any benefit. As you will see below, there are a huge number of esters, each providing a different release time.

Additional Advantages of Esters

It’s commonly cited that esters don’t affect or change the activity of the parent hormone in any way and only slow the release. However this is not strictly the case, and it’s been proven that longer esters are more anabolic than shorter esters. As the length of time a steroid is in your system increases, the amount of nitrogen retained is also increased, thereby increasing the overall anabolic effect.

In contrast, steroids with short esters causes a higher peak plasma level than a long ester does, meaning a higher level of the steroid can be obtained in the blood. A short ester, means you will get more bang for your buck.

These two distinct advantages demonstrate why it is advantageous to run both long and short esters during a cycle, both to obtain the highest level of anabolism possible, and also to provide peak plasma concentration. It also demonstrates why mixes and blends are superior to single ester steroid cycles.

Half-life of esters

Drug Active half-life
Formate 1.5 days
Acetate 3 days
Propionate 4.5 days
Phenylpropionate 4.5 days
Butyrate 6 days
Valerate 7.5 days
Hexanoate 9 days
Caproate 9 days
Isocaproate 9 days
Heptanoate 10.5 days
Enanthate 10.5 days
Octanoate 12 days
Cypionate 12 days
Nonanoate 13.5 days
Decanoate 15 days
Undecanoate 16.5 days


Chemical structure C2H4O2.

Ester Acetate

Acetate (acetic acid) is a short and fast acting ester. It has a half-life or 2-3 days. Steroids with this ester attached require daily administration.

Acetate esters are popular because they are inexpensive to produce and are of very low toxicity. Because of the short half-life, it also means that a cycle can be ended quickly if side effects appear and become intolerable.

The acetic acid tends not to cause any pain or irritation at the injection site.


Chemical structure C10H20O2.

Ester Decanoate

The decanoate ester is a structural derivative of decanoic acid, a straight chain fatty acid with anti-inflammatory properties. (Hence sensitive individuals will find the decanoate ester causes much less irritation at the injection site than steroids attached to shorter esters).

It is a large ester with a half-life of 15 days. This allows users to adopt a weekly or biweekly injection schedule. It is important to consider that that the decanoate will remain in the users system for quite a while after use of the steroid has ceased.

Decanoate is commonly attached to Nandrolone (Deca-durabolin) and can also be found in Sustanon.


Chemical structure C6H12O2.

Ester Isocaproate

This ester has a ‘middle of the road’ active life and is exclusively paired with testosterone. It’s commonly found in testosterone blends such as SustaGen (Sustanon). The purpose of isocaproate is to bridge the gap between the propionate ester and the decanoate ester, ensuring a steady release. It has a half-life of 9 days.


Chemical structure C3H6O2.

Ester Propionate

Also known as propionic acid, this ester will extend a hormones half-life to 4 and a half days.

Propionate is a short acting ester and allows for easy control and prevention of side effects. For this reason is generally recommended for a first time steroid user. It is usually administered every other day.

It is usually attached to testosterone and also commonly used in testosterone blends (such as Sustanon).


Chemical structure C11H20O2.

Ester Undecylenate

Undecylenate is a long ester chain that is almost identical to decanoate apart from an additional carbon atom which extends its release by an additional day. It is most commonly attached to Boldenone.

Administrations of hormones attached to the undecylenate only need to be repeated once every three or four weeks. It has a half-life of approximately 14 days.


Chemical structure C8H14O2.

Ester Cypionate

Cypionate is a large ester that is common attached to testosterone. It is a long-acting ester and extends the active life of the hormone to 7-8 days. The Cypionate ester has a long half life of approximately 12 days.

Cypionate is practically identical to the enanthate ester and is closely interchangeable, although it does have an additional carbon atom in the ester chain and therefore a slightly longer half-life than enanthate does.


Chemical structure C7H14O2.

Ester Enanthate

Enanthate is made up of 8 carbon atoms. It was the first ester that was attached to testosterone in order to provide a slower release rate. It is a large ester that is virtually identical to the cypionate ester and extends the half-life of a hormone to 10 days. Enanthate cause elevated blood plasma levels of the attached hormone to remain elevated for approximately 2-3 weeks. It is known for not causing pain or irritation at the injection site.


Chemical structure C9H10O2.

Ester Phenylpropionate

Phenylpropionate is a small sized ester that and has a half-life of only 4.5 days. Its release time sits in the middle of the short propionate and long cypionate esters. This allows the user to make advantage of some additional benefits such as the lack of requirement for frontloading or kickstarting a cycle, and also means it is excreted from the body quicker. Phenylpropionate is common used with testosterone or nandrolone.


Chemical structure C11H22O2.

Ester Undecanoate

The undecanoate ester was first studied back in 1967. It causes the attached hormone to release very slowly and has a half-life of 16.5 days. It can provide a sustained release of the hormone into the system for approximately 10 weeks. Therefore, it allows an infrequent administration schedule of once every 10 or 12 days while blood levels still remain stable. Undecanoate is not a common ester and also exclusively used by very experienced steroid users.


Chemical structure C26H34O4.

Ester Hexahydrobenzylcarbonate

This esters acts like a long-acting pro-drug of Trenbolone when administrated via intramuscular injection. It extends the release of Trenbolone to 14 days.

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