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Understanding Esters, Active-Life and Half-Life

Discussion in 'Anabolic Steroids & Prohormones' started by bigacb, Apr 6, 2011.

  1. bigacb

    bigacb Full Member

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    Steroid Half life's

    Anyone new to steroids may be wondering what this means, even some experienced steroid users may also be wondering what this means. So here in simple terms you can read and hopefully understand all about steroid half life's and what this term means.

    Basically every drug has a half life, steroids included. If for example, you were to inject 1000mg of testosterone cypionate once weekly, for 10 weeks, how would you know when you were "off"? Would you be "off" when you had finished your last dose? You would be able to calculate this from the half life of testosterone cypionate. The half life of testosterone cypionate is around 12 days. This means that 12 days from your last shot of 1000mg of testosterone cypionate (Time to start PCT? You decide.), your blood levels of testosterone cypionate will contain 500mg of the steroid. Another 12 days from then, i.e. 24 days from last dose, your blood levels will contain 250mg of the steroid. This amount then keeps halving every 12 days. At 48 days (almost 2 months) from your last dose, your blood levels will still contain 67.5mg of testosterone cypionate.

    Therefore you can clearly see that when you finish your cycle, even though you are not putting any steroids into your body, you may think that you are now "off", however you still have, and will still have for some time after your last dose, "active" blood levels of the steroid. Therefore you can plan what to use, how long for, and how long off your cycle, based on these half life's.

    Below a list of half-life's of the most commonly used steroids, esters and ancillary compounds.

    Oral steroids Drug Active half-life
    Anadrol / Anapolan50 (oxymetholone) 8 to 9 hours
    Anavar (oxandrolone) 9 hours
    Dianabol (methandrostenolone, methandienone) 4.5 to 6 hours
    Winstrol (stanozolol)
    (tablets or depot taken orally) 9 hours

    Depot steroids Drug Active half-life
    Deca-durabolin (Nandrolone decanate) 14 days
    Equipoise 14 days
    Finaject (trenbolone acetate) 3 days
    Primobolan (methenolone enanthate) 10.5 days
    Sustanon or Omnadren 15 to 18 days
    Testosterone Cypionate 12 days
    Testosterone Enanthate 10.5 days
    Testosterone Propionate 4.5 days
    Testosterone Suspension 1 day
    Winstrol (stanozolol) 1 day

    Steroid esters Drug Active half-life
    Formate 1.5 days
    Acetate 3 days
    Propionate 2 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

    Ancillaries Drug Active half-life
    Arimidex 3 days
    Clenbuterol 1.5 days
    Clomid 5 days
    Cytadren 6 hours
    T3 10 hours

    Active Life versus Half Life

    The confusion comes from the 2 terms being used synonymously when they should not be. "Half-life is not a reference for the total time a drug will be found active in the body. It may take several half-lives before the drug is completely inactive."

    Half-life: The period of time required for the concentration or amount of drug in the body to be reduced to exactly one-half of a given concentration or amount.

    Example: The half-life of anavar is 9 hours+/- (9 hours after oral administration of 50 mg of anavar, 25mg is still present in the body).

    Active life: Refers to the period in which the amount of a drug in the body is enough that it will still produce the desired effects for which it was administered. Or conversely, inhibit natural recovery of normal bodily function. It is dose dependent.

    Example: The active life of 1,000mg of testosterone decanoate would be more than one month. At day 30 after injection, 250mg or more of this drug would still be present in the body.


    I'm sure that if you have taken an interest in anabolic steroids you have noticed the similarities on the labeling of many drugs. Let's look at testosterone for example. One can find compounds like testosterone cypionate, enanthate, propionate, heptylate; caproate, phenylpropionate, isocaproate, decanoate, acetate, the list goes on and on. In all such cases the parent hormone is testosterone, which had been modified by adding an ester (enanthate, propionate etc.) to its structure. The following question arises: What is the difference between the various esterified versions of testosterone in regards to their use in bodybuilding?

    An ester is a chain composed primarily of carbon and hydrogen atoms. This chain is typically attached to the parent steroid hormone at the 17th carbon position (beta orientation), although some compounds do carry esters at position 3 (for the purposes of this article it is not crucial to understand the exact position of the ester). Esterification of an injectable anabolic/androgenic steroid basically accomplishes one thing, it slows the release of the parent steroid from the site of injection. This happens because the ester will notably lower the water solubility of the steroid, and increase its lipid (fat) solubility. This will cause the drug to form a deposit in the muscle tissue, from which it will slowly enter into circulation as it is picked up in small quantities by the blood. Generally, the longer the ester chain, the lower the water solubility of the compound, and the longer it will take to for the full dosage to reach general circulation.

    Slowing the release of the parent steroid is a great benefit in steroid medicine, as free testosterone (or other steroid hormones) previously would remain active in the body for a very short period of time (typically hours). This would necessitate an unpleasant daily injection schedule if one wished to maintain a continuous elevation of testosterone. By adding an ester, injections can be as infrequent as once per week or longer, instead of having to constantly re-administer the drug to achieve the desried effect. Clearly without the use of an ester, maintaining constant blood levels with an injectable anabolic/androgen would be much more difficult.

    Esterification temporarily deactivates the steroid molecule. With a chain blocking the 17th beta position, binding to the androgen receptor is not possible (it can exert no activity in the body). In order for the compound to become active the ester must therefore first be removed. This automatically occurs once the compound has filtered into blood circulation, where esterase enzymes quickly cleave off (hydrolyze) the ester chain. This will restore the necessary hydroxyl (OH) group at the 17th beta position, enabling the drug to attach to the appropriate receptor. Now and only now will the steroid be able to have an effect on skeletal muscle tissue.

    You can start to see why considering testosterone cypionate much more potent than enanthate makes little sense, as your muscles are seeing only free testosterone no matter what ester was used to deploy it.


    There are many different esters that are used with anabolic/androgenic steroids, but again, they all do basically the same thing. Esters vary only in their ability to reduce a steroid's water solubility. An ester like propionate for example will slow the release of a steroid for a few days, while the duration will be up to 15 days+/- with a decanoate ester. Esters have no effect on the tendency for the parent steroid to convert to estrogen or DHT (dihydrotestosterone: a more potent metabolite) nor will it effect the overall muscle-building potency of the compound. Any differences in results and side effects that may be noted by bodybuilders who have used various esterified versions of the same base steroid are just issues of timing.

    *Testosterone enanthate causes estrogen related problems more readily than Sustanon, simply because with enanthate testosterone levels will peak and trough much sooner. Likewise testosterone suspension is the worst in regards to gyno and water bloat because blood hormone levels peak so quickly with this drug (propionate included). Instead of waiting weeks for testosterone levels to rise to their highest point, here we are at most looking at a couple of days. Given an equal blood level of testosterone, there would be no difference in the rate of aromatization or DHT conversion between different esters. There is simply no mechanism for this to be possible.

    There is however one way that we can say an ester does technically effect potency; it is calculated in the steroid weight. The heavier the ester chain, the greater is its percentage of the total weight. In the case of testosterone enanthate for example, 250mg of esterified steroid (testosterone enanthate) is equal to only 180mg of free testosterone. 70mgs out of each 250mg injection is the weight of the ester. If we wanted to be really picky, we could consider enanthate slightly MORE potent than cypionate (I know this goes against popular thinking) as its ester chain contains one less carbon atom (therefore taking up a slightly smaller percentage of total weight). Propionate would of course come out on top of the three, releasing a measurable (but not significant) amount more testosterone per injection than cypionate or enanthate.


    While the advent of esters certainly constitutes an invaluable advance in the field of anabolic steroid medicine, clearly you can see that there is no magic involved here. Esters work in a well-understood and predictable manner, and do not alter the activity of the parent steroid in any way other than to delay its release. Although the lure surrounding various steroid products like testosterone cypionate, Sustanon, Omnadren etc. certainly makes for interesting conversation, realistically it just amounts to misinformation that the athlete would be better off ignoring. Testosterone is testosterone and anyone who is going to tell you one ester form of this (or any) hormone is much better than another one should do a little more research, and a lot less talking.


    Sustanon: The "king" of testosterone blends.
    The four different testosterone esters in this product certainly look appealing to the consumer, there is no denying that. But for the athlete I think it is all just a matter of marketing (Hell, why buy one ester when you can get four?). In clinical situations I can see some strong uses for it. If you were undergoing testosterone replacement therapy for example, you would probably find Sustanon a much more comfortable option than testosterone enanthate. You would need to visit the doctor less frequently for an injection, and blood levels should be more steadily maintained between treatments. But for the bodybuilder who is injecting 4 ampules of Sustanon per week, there is no advantage over other testosterone products. In fact, the high price tag for Sustanon usually makes it a very poor buy in the face of cheaper testosterone enanthate/cypionate. Bodybuilders should probably stop looking at the four ester issue, and stick with totals (Sustanon is just a 250mg testosterone ampule). If you could get nearly double the milligram amount for the same price with enanthate, this is the better product to go with hands down. Leave the high priced stuff for the guys who don't know any better.

    Acetate: Chemical Structure C2H4O2.
    Also referred to as Acetic Acid; Ethylic acid; Vinegar acid; vinegar; Methanecarboxylic acid. Acetate esters delay the release of a steroid for only a couple of days. Contrary to what you may have read, acetate esters do not increase the tendency for fat removal. Again, there is no known mechanism for it to do so. It is the steroid and not the ester. This ester is used on oral primobolan tablets (metenolone acetate), Finaplix (trenbolone acetate) implant pellets, and occasionally testosterone.

    Propionate: Chemical Structure C3H6O2.
    Also referred to as Carboxyethane; hydroacrylic acid; Methylacetic acid; Ethylformic acid; Ethanecarboxylic acid; metacetonic acid; pseudoacetic acid; Propionic Acid. Propionate esters will slow the release of a steroid for several days. To keep blood levels from fluctuating greatly, propionate compounds are usually injected from every day to three times weekly. Testosterone propionate and methandriol dipropionate (two separate propionate esters attached to the parent steroid methandriol) are popular items.

    Phenylpropionate: Chemical Structure C9H10O2.
    Also referred to as Propionic Acid Phenyl Ester. Phenylpropionate will extend the release of active steroid a few days longer than propionate. To keep blood levels even, injections are given at least twice weekly. Durabolin is the drug most commonly seen with a phenylpropionate ester (nandrolone phenylpropionate), although it is also used with testosterone in Sustanon and Omnadren.

    Isocarpoate: Chemical Structure C6H12O2.
    Also referred to as Isocaproic Acid; isohexanoate; 4-methylvaleric acid. Isocaproate begins to near enanthate in terms of release. The duration is still shorter, with a notable hormone level being sustained for approximately one week. This ester is used with testosterone in the blended products Sustanon and Omnadren.

    Caproate: Chemical Structure C6H12O2.
    Also referred to as Hexanoic acid; hexanoate; n-Caproic Acid; n-Hexoic acid; butylacetic acid; pentiformic acid; pentylformic acid; n-hexylic acid; 1-pentanecarboxylic acid; hexoic acid; 1-hexanoic acid; Hexylic acid; Caproic acid. This ester is identical to isocarpoate in terms of atom count and weight, but is laid out slightly different (Isocaproate has a split configuration, difficult to explain here but easy to see on paper). Release duration would be very similar to isocaproate (levels sustained for approximately one weak), perhaps coming slightly closer to enanthate due to its straight chain. Caproate is the slowest releasing ester used in Omnadren, which is why most athletes notice more water retention with this compound due to blood level saturation.

    Enanthate: Chemical Structure C7H14O2.
    Also referred to as heptanoic acid; enanthic acid; enanthylic acid; heptylic acid; heptoic acid; Oenanthylic acid; Oenanthic acid. Enanthate is one of the most prominent esters used in steroid manufacture (most commonly seen with testosterone but is also used in other compounds like Primobolan Depot). Enanthate will release a steady (yet fluctuating as all esters are) level of hormone for approximately 10-14 days. Although in medicine enanthate compounds are often injected on a bi-weekly or monthly basis, athletes will inject at least weekly to help maintain a uniform blood level.

    Cypionate: Chemical Structure C8H14O2.
    Also referred to as Cyclopentylpropionic acid, cyclopentylpropionate. Cypionate is a very popular ester in the U.S., although it is scarcely found outside this region. Its release duration is almost identical to enanthate (10-14 days), and the two are likewise thought to be interchangeable in U.S. medicine. Althletes commonly hold the belief than cypionate is more powerful than enanthate, although realistically there is little difference between the two. The enanthate ester is in fact slightly smaller than cypionate, and it therefore releases a small (perhaps a few milligrams) amount of steroid more in comparison.

    Decanoate: Chemical Structure C10H20O2.
    Also referred to as decanoic acid; capric acid; caprinic acid; decylic acid, Nonanecarboxylic acid. The Decanoate ester is most commonly used with the hormone nandrolone (as in Deca-Durabolin) and is found in virtually all corners of the world. Testosterone decanoate is also the longest acting constituent in Sustanon, greatly extending its release duration. The release time with Decanoate compounds is listed to be as long as one month, although most recently we are finding that levels seem to drop significantly after two weeks. To keep blood levels more uniform, athletes (as they have always known to do) will follow a weekly injection schedule.

    Undecylenate: Chemical Structure C11H20O2.
    Also referred to as Undecylenic acid; Hendecenoic acid; Undecenoic acid. This ester is very similar to decanoate, containing only one carbon atom more. Its release duration is likewise very similar (approximately 2-3 weeks), perhaps extending a day or so past that seen with decanoate. Undecylenate seems to be exclusive to the veterinary preparation Equipoise (boldenone undecylenate), although there is no reason it would not work well in human-use preparations (Equipoise certainly works fine for athletes). Again, weekly injections are most common.

    Undecanoate: Chemical Structure C11H22O2.
    Also referred to as Undecanoic Acid; 1-Decanecarboxylic acid; Hendecanoic acid; Undecylic acid. Undecanoate is not a commonly found ester, and only appears to be used in the nandrolone preparation Dynabolan, and oral testosterone undecanoate (Andriol). Since this ester is chemically very similar to undecylenate (it is only 2 hydrogen atoms larger), it has a similar release duration (approximately 2-3 weeks). Although this ester is used in the oral preparation Andriol, there is no reason to believe it carries any properties unique of other esters. Andriol in fact works very poorly at delivering testosterone, bolstering the idea that oral administration is not the idea use of esterified androgens.

    Laurate: Chemical structure C12H24O2.
    Also referred to as Dodecanoic acid, laurostearic acid, duodecyclic acid, 1-undecanecarboxylic acid, and dodecoic acid. Laurate is the longest releasing ester used in commercial steroid production, although longer acting esters do exist. Its release duration would be closer to one month than the other esters listed above, although realistically we are probably to expect a notable drop in hormone level after the third week. Laurate is exclusively found in the veterinary nandrolone preparation Laurabolin, perhaps seen as slightly advantageous over a decanoate ester due to a less frequent injection schedule. Again athletes will most commonly inject this drug weekly, no doubt in part due to its low strength (25mg/ml or 50mg/ml).


    All the evidence points to the use of short estered AAS injectables, versus long estered AAS injectables, as being the fastest way to recover natural testosterone levels post cycle.

    *Note: The information above was compiled from a number of different authors and websites.

    This was taken from another board by a guy called 'The Bouncer' but i thought there was alot of useful information in there for beginners and maybe it might stop the same questions being asked over and over [​IMG]
    schtaqua, Johnm4c, MuscleN and 8 others like this.
  2. bigacb

    bigacb Full Member

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    Don't think all of the half life's are spot on someone feel free to change... :)
  3. brownie


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    well done, definitely sticky worthy.......
  4. Greyphantom

    Greyphantom Moderator

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    there is some conjecture as to half lives, most of it waaaay above my head but I have heard ranges for test e from 5 to 11 days... nice post and good info though...
    HLSXN likes this.
  5. Prodiver

    Prodiver Top Contributor

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    It's even a bit more complicated:

    If an ester has a half life of 7 days and you inject again at one week, you have half the original load, plus the new load.

    Calculating the actual load on any day with repeat injections and different half-lives requires a bit of maths!
    Weeman likes this.
  6. Greyphantom

    Greyphantom Moderator

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    when you say it like that it all seems so simple :D :D
    bigacb likes this.
  7. Prodiver

    Prodiver Top Contributor

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    I'll see if I can develop an easy to use formula...
  8. Greyphantom

    Greyphantom Moderator

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    wasnt there an exel spreadsheet that had a list of esters and you could plug in numbers and it would spit out total amounts that were in your blood... I dont think it was exact but it was pretty good...
  9. Alex

    Alex Account Suspended

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    This what you mean?

    Roid Calculator - half lifes steroids ester half-life

    I came across that before but got confused so gave up lol
  10. Prodiver

    Prodiver Top Contributor

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    Seems OK to me.

    Not sure about the differences in the delts, or about the waste factor, though.

    The maths of exponential curves isn't easy!

    The whole thing's a bit of a minefield, because while many drugs do follow the half-life law to a degree, they are eventually cleared from the body, but true half-life substances like radioisotopes never disappear completely - true half-lives are asymptotic, never reaching zero.
    JW007 likes this.
  11. Simon

    Simon Moderator

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    Have stickied this thread as I think it will be useful to lots of members. Thanks for the contribution bigacb.
    bigacb likes this.
  12. bigacb

    bigacb Full Member

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    Came across it accidentally but was impressed how much of an easy read it was and sets it out in Layman's terms.
  13. Dig

    Dig Mod & Powerlifting Expert Moderator

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    Example: The active life of 1,000mg of testosterone decanoate would be more than one month. At day 30 after injection, 250mg or more of this drug would still be present in the body.

    I am 99.9% sure ive seen Mars say a few times that it doesnt actually work like this....
  14. B|GJOE

    B|GJOE Diet Expert Expert

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    Right! I'm still not convinced by all this half life, active life stuff, and it is still confusing me.

    I've seen the Op's text splattered all over the net, so it's a copy and paste job. Valuable, but I'm still not getting it.

    To help me understand this, I need to know how long it takes the body to completely break down hormone once it is in the body.

    The purpose of esterification is to slow down the release of the hormone from the injection site. The half life seems to be determined by the ester and not the hormone. So am I correct in assuming that the half life is the time it takes to release 50% of the hormone from the site injection site, or is it the time that the hormone is active in the body after it released into the blood from the injection site?

    Hopefully I'll get across what I want here.

    I am assuming that once the blood has picked up some hormone from the injection site and released it into the blood stream, then it is the same hormone regardless of the ester?

    If this is the case, then the breakdown of the hormone will be the same, regardless what ester it was attached to before it was picked up and released into the blood?

    If the above is the case, then how long does the body take to breakdown the hormone?

    Lets use some hypothetical numbers here.

    Lets say that the body breaks down hormone in 24 hours after it is released into the blood. Lets say that test suspension goes directly into the blood due to no ester, then the hormone will be all gone and no longer active after 24 hours.

    Now lets say we inject 100mg of test E which takes 10 days to release all of the hormone into the blood at approximately 10mg a day. So day 1 we have 10mg in the blood, but this will be broken down in 24 hours, when the next 10mg will be released into the blood and so on. Therefore after day 11 all hormone will be gone and inactive.

    I've probably made a lot of incorrect assumptions here, but I have also read that the active life of test e is 10 days, and i have also read the half life is anything from 6 to 12 days.

    Now tbh I'm not buying into this half life crap! Esterification is to slow the release, not to extend the active life of hormone once it is in the body. I really don't see how I could inject 500mg on day 1, and have 62 and half mg of active hormone in my body 30 days later. It don't make sense to me.

    Will someone please make this simple, or is the whole bbing community just as confused, and is just regurgitating the same stuff verbatim, without really thinking about it?

    P.S. If it is the case that the half life is the time it takes to release half the hormone from the site, then how does this work. Does the body pick up a percentage of the total hormone at the site, or a roughly fixed quantity?

    If it is a percentage, then the maths gets even more confusing.

    Lets say 10% a day hypothetically. 100mg

    After day 1 90mg
    After day 2 81mg
    After day 3 73.9mg

    And so on
  15. B|GJOE

    B|GJOE Diet Expert Expert

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