Aromatase Inhibitors For Men – Complete Guide To Arimidex, Aromasin, Femara

With anabolic steroids, you interfere in the natural hormonal balance of your body and get all the consequences. Aromatase Inhibitors make the interference smoother and prevent all the possible harm. Don't want to get moobs and turn into an acne-covered walking heart attack time bomb? You need AI's. And this guide you can learn everything you need to know about them.


On cycle, your testosterone converts to estrogen, and it’s in no way a good thing. You need to counter the conversion to avoid some disgusting side effects. There’s no better option than Aromatase Inhibitors for that. However, if you abuse them, you risk getting an insufficient level of estrogen. It is even worse to your gains. A proper “insurance” with AI demands some understanding of the process.

Why Estrogen Is So Important

You already know that men have testosterone. I bet you do. However, men have small amounts of estrogen, the female sex hormone, as well. That is a piece of surprisingly less common knowledge. Estrogen is vital for numerous processes in the male body, including muscle growth.

The key thing here is the ratio of estrogen and testosterone. Naturally, it is about 1:10, meaning that you need to have 10 times more testosterone than estrogen to be a man. The numbers are, of course, approximate – they change throughout your life, depending on age, lifestyle, diet, and body stats.

How Steroids Affect Your Hormonal Balance

Anabolic steroids enhance your testosterone level to give you extreme gains at the gym, make you massive, shredded, and strong. In exchange, most steroids mess up your hormonal system. In one way or another, you get the imbalanced ratio between testosterone and estrogen. It bears two main risks for an athlete on gear: having too much estrogen and having not enough estrogen.

Effects Of Excessive Estrogen Level:

Too much estrogen in your body may lead to the development of several notorious hormonal issues. It hits your whole body in a complex strike, and most systems suffer significant damage:

  • Mood swings, uncontrolled emotions;
  • Decreased libido;
  • Gynecomastia;
  • Severe acne;
  • Heart issues;
  • Prostate enlargement (possibly leading to cancer);
  • Balding;
  • Edema, aka puffiness (the result of water retention).

Effects Of Insufficient Estrogen Level:

Decreased estrogen in the male body causes a chain reaction that may lead to a major hormonal imbalance. Estrogen itself is a vital hormone for muscle growth. Without it, all your testosterone cycling will give zero to none results. Here are some additional effects of decreased estrogen:

  • Weaker bones and joints;
  • Decreased Libido;
  • Immunity decrease;
  • Zero muscle and strength gains;
  • Less pumping effect.

Doesn’t sound any better, right? At least NOW you know that it is possible. You’d be surprised, how many athletes believe that all estrogen is bad, because “it’s a girls hormone”. Now that you know how it works, let’s switch to the process that defines these levels – the aromatization.

What Is Aromatization

In short, it’s a process of converting your androgens (like testosterone) to estrogens (mostly estradiol). Aromatization starts when you have excessive male sex hormones. Your body simply doesn’t know how to deal with it, panics, and starts to transform it into a different hormone. A unique enzyme, the aromatase, is responsible for the process. It “lives” all around your body, but mostly in these areas:

  • Breast tissue;
  • Adrenals;
  • Testicles;
  • Blood vessels;
  • Fat tissue (fatter people tend to be heavy aromatizers).

Aromatase enzymes don’t mean to harm you, they just do their simple work. Unfortunately, they do it mostly around your man boobs. The results of their activity just don’t get along well with bodybuilding in general.

Aromatisation Defining Factors

The process is even more complicated than it seems to be. People have different aromatization abilities. Some don’t experience it at all, and some call themselves «heavy aromatizers» for a reason. These 3 key factors define, how much you will aromatize:

Most And Least Aromatizing Steroids

You also need to know that some steroids aromatize more than the others. Note that this list is here to give you a basic concept – it’s obviously not complete.

Most Aromatizing Steroids:

Less Aromatizing Steroids:

Keep in mind that you are unlikely to run an Anavar solo cycle. Most of the time you have to complete your stack with testosterone to prevent the shutdown.

Boldenone And Aromatase Inhibitors

One steroid stands out from any list in terms of interaction with AI. It is Boldenone. Taking Aromatase Inhibitors with Boldenone is extremely dangerous for your health. Avoid it at all costs. Boldenone lowers your estrogen levels by itself during the cycle. If you add AI to an already suppressed estrogen, you risk experiencing all kinds of unpleasant side effects.

With Boldenone AND Aromatase Inhibitors, your bones will soon get weaker, your liver will turn inside out, and your nervous system will resemble one of a 12-year-old girl, not to mention the mental fog galore.

The worst part is that the effect might be irreversible. Seriously, don’t take AI after Boldenone, that’s a life-threatening mixture.

Difference Between SERMs and AI

Many people seem to make a crucial mistake – think of selective estrogen receptor modulators (Nolvadex, Clomid, Raloxifene) and aromatase inhibitors as of the same kind of substances. It’s the result of the unprofessional use of the term «anti-estrogens» on the web. People mistakenly associate it with AI and SERMs at the same time.

You can’t replace Nolvadex with Aromasin or Femara with Clomid – they have a completely different mechanism of action.

SERMs are the last defense line. They are designed to block estrogen receptors and prevent the administering of estrogen in your body when the levels are ALREADY through the roof. That’s why SERMs like Nolva or Clomid are for the PCT phase when you need to recover. It’s a whole different subject – here you can read our complete PCT guide. In fact, about 20-30 years ago athletes used to run Nolva ON cycle – it worked for some of them, but was harsh on gains.

Aromatase Inhibitors attack proactively and inactivate the aromatase enzymes themselves. This way your body can’t produce estrogen in dangerous, unhealthy amounts. Your receptors can administer only the small amount of estrogen leftovers. It also happens much faster, since SERMs need some time to build up in your body. Most AI need just 2 hours to peak in their action. That’s why SERMs are best for PCT, and AI are perfect to take them mid-cycle.

Types Of Aromatase Inhibitors

Many articles on the Web offer you just one classification which I personally find a bit tricky: Steroidal and Non-steroidal aromatase inhibitors. Here is an extremely simplified version of it:

Steroidal AI act in an irreversible way. They modify the enzyme to the point when it’s altered so much that it can’t perform its main function. Steroidal AI are:

  • Aromasin (Exemestane);
  • Testolactone and Formestane (Generation 1 AI, no longer available).

Non-steroidal AI during the inhibition process bind to enzymes and deactivate them. The process is reversible, which means that you should not expect a spike in estrogen levels. Non-steroidal AI are:

  • Letrozol (Femara);
  • Arimidex (Anastrozol);
  • Rivizor (Vorozole).

For the medical experts who study these compounds theoretically in terms of cancer prevention and regular TRT, this classification is just enough. However, you are probably going to use AI for your anabolic steroids cycle. You need to range them in terms of power and dosage. The most powerful AI available now is non-steroidal and reversible Letrozole (Femara). To avoid misunderstandings, let’s look at the 3 most popular Aromatase Inhibitors on the market in better detail.

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Letrozole (Femara)

Letrozole is probably the most powerful of all AI. It is medically proven to block 98.4% aromatase cytochromes and reduce the concentration of estradiol in your blood. It’s so powerful that most experienced athletes and doctors recommend taking it every 3 days, not every day. At the same time, Letrozole doesn’t affect other hormones and works selectively. You can use it during your cycle, just make sure that it doesn’t react with your gear in a bad way. And it’s plain dangerous to run Letrozole on PCT because it can react with SERMs and lead to estrogen shutdown. For more details, see my complete Femara guide.

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Arimidex (Anastrozole)

Anastrozole (on the market as Arimidex) is a long-standing rival for Letrozole. Although Letrozole has better inhibition capacity, two compounds are mostly similar. Both are classic aromatase inhibitors, created for breast cancer treatment. Both are non-steroidal and reversible. Both can be bought in our shop and we guarantee the best quality. Buy Arimidex and see for yourself. They even act in the same way, deactivating the aromatase enzymes. Two key areas where differences are notable are side effects and dosage. Letrozole comes in 2,5mg pills and Anastrozole – in 1mg pills. Anastrozole may cause blood pressure spikes, pain in the bones, or mental side effects. Letrozole is more likely to lead to depression, sleep issues, and an upset stomach. Which AI is better?

We have no idea, whether Arimidex is better than Letrozole, and vice versa. Seriously, for about 15 years now, the medical community is divided on this topic.

Some specialists prefer Letrozole, and studies prove that it is superior to Anastrozole. At the same time, other specialists prefer Anastrozole and base their choice on other studies, that support Anastrozole’s superiority. Even recently published results of a full scale (65 months and 4000+ patients) medical study which aimed at a direct comparison between Letrozole and Anastrozole (in cancer treatment, of course) has proven that differences between them are insignificant. It means that the choice is all up to you.

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Aromasin (Exemestane)

Exemestane is wildly different from other AI options above. It also was created for the prevention of cancer, but it is steroidal. It functions as a false substrate for the aromatase enzyme. The difference from non-steroidal AI is that the bond between the compound and the enzyme is irreversible, and the deactivation process leads to the deactivation of the compound as well. That’s why Aromasin is called a suicide inhibitor. With all that taken to account, Exemestane is still one of the most popular AI options.

You should be extra careful not only when you take Aromasin, but also when the course ends. Your estrogen can skyrocket back again.

It’s a rare effect and athletes rarely report it, but you should be aware of it anyway. On cycle, you don’t need more than 12,5mg every other day. In some severe cases, when gynecomastia is already visible, you might need up to 25mg daily. Note that the boosted 25mg course should last just 1 week instead of 2 or 3. You can also read my complete guide on Aromasin.

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Aromatase Inhibitors Side Effects

AI affect your hormonal system violently and you can’t escape some side effects of it. Luckily, on a short and moderate course, with all precautions taken at the right time, you can lower the side effects significantly. Here are the key areas that get hit:

CNS Side Effects

Central Nervous System is the first one to take the hit. Only high doses of AI can trigger issues, like a general nervous state and aggressive behavior. However, some athletes report sleep issues even in the frames of common dosage. You wake up after a healthy 8 hours of sleep and feel like you had no sleep for a whole week. OR you go to your bed after a hard day and can’t fall asleep at all. That’s a typical story for Aromatase Inhibitors. To counter the fatigue and insomnia you can slightly lower your dose, in most cases that will be enough to balance your nervous system. Just don’t try to fight sleepiness with coffee and energy drinks – they exhaust your CNS even more without any positive effect.

Cardiovascular Side Effects

You intervene in your blood work, and your heart is not ready for the changes. Especially when you work out hard and need to keep your BPS in the effective zone. While blood pressure spikes are a possible side effect of AI, hopefully, serious consequences, like a heart attack, haven’t been reported. To treat your heart right, just avoid alcohol on AI and pay extra attention to chest pains.

GI System Side Effects

Your stomach and intestines are not happy about the aggressive compound they have to deal with either, but since all most popular AI are oral, your digestive system just can’t escape it. GI side effects may include:

  • Nausea;
  • Vomiting;
  • Flatulence;
  • Diarrhea;
  • Loss of appetite.

Liver Side Effects

AI compounds are toxic to your liver, even though the effect is not as bad as one from 17-alpha-alkylated steroids. Toxicity is mostly mild, but in worst cases, athletes reported a drop of HDL level (the «good» type of cholesterol) to the unhealthy point of 20 mg/dl.

Other Side Effects Of AI

All popular AI work selectively in your body, but the whole body feels complex consequences. Here is what AI can lead to as well:

  • Drying, tendon ruptures;
  • DVT;
  • Headaches;
  • Attention blur;
  • Rise in creatinine levels;
  • Lowered immunity;
  • Allergic reactions.

The good news is, most AI side effects are dose-dependent and individual – just like most other compounds in bodybuilding.

How To Avoid Aromatase Inhibitors Side Effects

There is no magic pill to avoid any consequences of AI usage. It’s highly individual since we’re talking about the hormonal system. The general advice would be these traditional points:

  • Maintain junk food-free and healthy diet;
  • Stay away from alcohol and drugs;
  • Pay extra attention to your health, notice any unusual pain, physical sensations, and mental state.

In case you notice something bad and it doesn’t go away when you lower your dose, you can legitimately replace one AI with another. You can replace Letrozole with Arimidex or Aromasin, and vice versa. You’ll probably notice results in 2-3 days since most AI have a short half-life. If it doesn’t help, just drop the course.

AI Side Effects are not as dangerous as AI effects themselves in case of abuse. Estrogen insufficiency can lead to even more serious consequences.

How To Track AI Effects

The best way to avoid any surprises is to keep your estrogen under control, and by that, I mean constantly being aware of its level in your blood. The best way to achieve it is regular medical testing. Yes, you NEED to go to the hospital and get a test. And just one blood work won’t be enough. You have to take 3 of them:

When Target
Test #11 month before the cycleTo see your results when you’re at least relatively clean
Test #22-3 weeks into the cycle (on short gear);
3-4 weeks on long-acting compounds.
To estimate the current estrogen levels on gear, your individual speed of the process, and to adjust the AI dosage.
Test #3A week after the last AI pillTo see if your estrogen and testosterone levels got back to normal (like in Test #1)

The average level of estrogen for an adult man is around 160 E2. On Test №2 most athletes notice a raise for about 20 points, up to 180 E2. The reaction to it is highly individual though. Some feel like garbage even on 15 E2 surpluses. Some people don’t notice it at all.

It all depends on your estrogen receptors’ capacity and genetics. To get the full professional interpretation of the results, you need to ask your doctor about it.

Reasons To Avoid Medical Tests on AI

None of them exist. Period. If you have time to go to the gym multiple times a week, so you can find an hour or two to go to the nearest medical center. If you have money to buy anabolic steroids (and not the cheapest ones), you probably can find some cash to spend on the testing. Keep in mind that if you lose control, surgical removal of gynecomastia will take you much longer, and will cost you several thousand Dollars – multiple times more, than a test that could help you avoid it.

Personal Opinion On Aromatase Inhibitors

Aromatase Inhibitors are the most dangerous set of compounds that you can come across in the bodybuilding world. Not because of power – more so because of their hideous nature. However, desperate times demand desperate measures. When you mess up your hormonal balance, you need strong compounds to get the balance back. Just keep in mind that if you try too hard, your general health can be ruined even further. Luckily, going on gear demands discipline with any compound. It will be a great idea to buy Anastrozole or other options in our shop and to test them to find what suits you best.

It’s hard to choose the best available compound though. I would say that for regular long-term TRT you have to stick with Anastrozole. Reserve Letrozole for those, whose liver reacts badly to other options. Yes, common TRT doses are significantly smaller, about 50-150mg per week. Athletes inject 250-500, up to 750mg per week to get extra gains. There IS a difference. That’s why you’ve got to choose the right compound yourself, depending on the type of gear that you’ve cycled. The wrong AI is still better than no AI at all.


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