Aromatase Inhibitors: Why and when to use


Active member
If youve been on the board for virtually any amount of time you've undoubtedly seen these questions posed...

"Do I really need an AI?"
"Whats the dosing and when do I start?"
"Which is the best?" to help the newcomers and those who may have very little knowledge to the process of aromatization, heres my take on the whole process.

The process in which your free testosterone binds with the aromatase enzyme and converts to estradiol. Thats as sinple as I can put it.

The aromatase inhibitor (either exemastane, anastrazole, or letrozole) is administered and binds with the aromatase enzyme disabling the cell from aromatizing free testosterone and, therefore, preventing a rise in unwanted estrogen.

This is the most popular and user friendly of AIs and offers a number of added benefits. It does not produce a negative impact on lipid profiles and it has been shown to increase not only free testosterone but also IGF (insulin growth factor) levels. It is also a suicidal aromatase inhibitor which means after it binds with the aromatase enzyme it destroys the cell. A general rule of thumb dosing protocol is 12.5mg every other day. Of course this is very dependant on user and is only a starting off point.

Ive used arimidex in the past and it will work for sure, bu it is not as good a choice of AI as aromasin, as it is not a suicidal inhibitor and only temporarily prevents the aromatase enzyme from estrogen conversion. Once you stop taking Arimidex, you are at risk of experiencing an estrogen rebound wherein all those aromatase cells that were inhibited during the Arimidex use are now freed up and working hard to aromatize any lingering free testosterone. Arimidex has also been shown to significantly decrease bone mineral content and negatively affect HDL cholesterol levels. General dosing protocol is 0.5mg every other day.

This is by far the most potent and difficult to dial in. I wouldnt recommend it for the typical anti-estrogen use on cycle. It is more useful for those who are gyno prone to have on hand as Letrozole is amazing at stripping the body of estrogen during gyno flares. It is also better suited for those in a conpetition prep during their final weeks to strip the body of excess water related to estrogen levels. Letrozole has been shown to increase testosterone production through an increase in leutinizing hormone and follicle stimulating hormone as well, although it has also been shown to decrease bone mineral content and decrease HDL cholesterol levels. General dosing for letrozole is around 0.5-1.0 mg every other day.

So to answer the initial three questions that are so often asked..

1.YES you really should run an AI with every cycle. It will not limit your gains, on the contrary, it will iNCREASE them slightly.

2. You should start the use of an AI from day one of your cycle. Choose which you feel is best for you... aromasin 12.5mg eod, arimidex 0.5mg eod, and letrozole 0.5mg eod.

3. It all comes down to personal preference and it seems most people have the same belief in regards to this question...
AROMASIN is king in the world of aromatase inhibitors.

Hope this helps someone out


Active member
Thank you for explaining it in a way everyone can understand

That was my main goal. Theres a ton of information out there on this subject but its good to get it all in one place in simplified terms for everyone. Some of the info can be tough to understand if youre new and unfamiliar with the terminology


Great post! Well thought out an organized. Should be a must read and sticky IMO.

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Awesome post. If I had been able to have solid information like this on my first cycle I would have known how important AI's are while on. I definitely suffered effects of high estrogen and ended up looking like the god damn Michelin man for a bit. LETS GET THIS STICKIED so anyone new to the forum can get this information immediately.


Founding Member
Super Moderator
I encourage everyone to read this once, twice and then again. This is damn nice information and really provides a thorough explanation that is highly detailed yet easy to understand. Great post molnar!