If you want to know what clenbuterol is, how it works, how effective it is, and if it’s dangerous, then you want to read this article.


Hang around in the gym long enough and you’re going to hear about clenbuterol.

Like steroids, “clen” is extremely popular in the world of bodybuilding and is the “go-to” cutting drug for many of the people that step on stage.

Thus, it’s not surprising that it’s also a hot commodity among the general fitness crowd.

If you want to shred fat as quickly as possible without losing muscle, the pitch goes, then you want to hop on the clenbuterol train.

Or do you?

Poke around on the Internet and you’ll find people that think otherwise.

Clenbuterol, they say, isn’t actually all that powerful of a fat burner and is bad for your health to boot, and for your heart in particular, even when used in moderate doses.

Who’s right?

How much can this drug really boost your fat loss? Should you take warnings about side effects seriously, or are they exaggerated? Is there anything else you should know before deciding for or against clen?

Well, you’re going to get answers to all of those questions and more in this article.

By the end, you’re going to know exactly how clenbuterol works, how effective it really is, how likely it is to harm your body, and more.

Let’s get to it.

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What Is Clenbuterol and How Does It Work?

Clenbuterol is a powerful stimulant that increases metabolic rate and fat burning.

It’s sold under different names, like Dilaterol, Spiropent, and Ventipulmin, but most people just refer to it as “clen” or “bute.”

It was originally developed in the 1970’s as a veterinary drug to treat respiratory disorders in horses and other animals. It acts as a bronchodilator, meaning that it relaxes the muscles around airways to make breathing easier.

For a short time, clenbuterol was also marketed as a nasal decongestant and asthma medication for humans. It’s still used as respiratory medication in some countries, but most have switched to safer, more effective alternatives.

Now, how the hell did clen go from something to help horses run better to one of the most popular cutting drugs in all of bodybuilding?

Well, clenbuterol binds to the same receptors that respond to epinephrine in your body, but clenbuterol produces even greater effects, including fat burning.

Furthermore, clen also binds to muscle cells and stimulates muscle protein synthesis, which is why it also helps you preserve muscle while cutting.

Why Do People Take Clenbuterol?

Most people take clenbuterol for one of two reasons:

  1. To improve athletic performance.
  2. To lose fat faster while preserving muscle.

There’s an ongoing debate as to whether it boosts physical performance, but as of now, most studies indicate it probably doesn’t.

There’s no doubt that it speeds up fat loss, though.

Both animal and human research has confirmed that clenbuterol raises metabolic rate and stimulates fat burning, and although it isn’t a steroid, studies show that it stimulates muscle protein synthesis, which will indeed help you retain lean mass while in a caloric deficit.

This is why clenbuterol is all the rage among bodybuilders.

Some even claim that its anabolic effects are powerful enough to enhance muscle building, but this isn’t likely given what we know about it scientifically as well as anecdotally.

Now, just how powerful clenbuterol is as a fat burner is matter of dispute.

Many seasoned users claim it boosts your basal metabolic rate (BMR) by about 10%, and I don’t know of any research that can either corroborate or refute this number. That said, it seems reasonable based on decades of anecdotal evidence.

That brings us to one of the big criticism of the drug: given its health risks (which we’ll talk more about soon), a ~10% increase in BMR really isn’t all that great.

For example, let’s say you’re a muscular guy and your BMR is fairly high. 2,200 calories per day, let’s say. Adding clen to your cut would increase this by about 220 calories, which would help you lose no more than a half of a pound of fat per week.

You also aren’t supposed to take clen for more than 4 to 6 weeks at a time because your body builds a tolerance to it, diminishing its effectiveness.

Thus, a “cycle” of clen will help you burn maybe an extra 3 pounds of fat, and that’s only if you have your diet 100% on point. Or you could just stay drug-free and extend your cut by a few weeks to achieve the same effect, and not have to worry about potential side effects…

Is Clenbuterol Safe?

shredded man in gym

Most of the research on clenbuterol has been done on animals, so we don’t know enough about how seriously it can affect us humans.

What we do know, though, is it doesn’t look good, which is why clen isn’t approved for human consumption in most countries.

Here’s a list of the potential side effects:

  • Nausea
  • Nervousness
  • Dizziness
  • Drowsiness
  • Dry mouth
  • Facial flushing
  • Headache
  • Heartburn
  • Increased sweating
  • Insomnia
  • Lightheadedness
  • Muscle cramps
  • Vomiting
  • Chest pain

Everyone’s sensitivity to clenbuterol varies, but most will likely experience at least some of these problems when using it.

Here’s what else we know…

Clenbuterol Is Probably Bad For Your Heart

The biggest question most people have about clen is if it’s bad for your heart.

And the answer is yes.

First, as clen is a powerful stimulant, it can spike your blood pressure and keep it greatly elevated for extended periods of time.

This, in turn, can increase your risk of left ventricular hypertrophy, or LVH, which is the thickening of the wall of the heart’s left pumping chamber (ventricle). LVH is a major risk factor for heart disease and is also linked with an increased risk of arrhythmias and sudden death.

Unfortunately, as there haven’t been any long-term human studies on clenbuterol use, we don’t know how much clen it takes to get there. We’re going off case studies of people that wound up hospitalized after abusing clen.

Second, there’s evidence that clenbuterol can kill heart cells, which, of course, increases your risk of heart disease.

It’s worth noting that these cases involved people taking very large doses of clenbuterol (several times higher than even most bodybuilders would recommend), but lower doses may physically damage your heart as well. We just don’t know.


Clenbuterol Interferes with Your Sleep

woman sleeping

I mentioned earlier that clenbuterol is a powerful stimulant, and I meant it.

Not only does it spike your metabolic rate, it also stays in your system for far longer than milder drugs like caffeine and ephedrine.

Specifically, research shows that clen can remain in your blood for up to 24 to 26 hours, which is why it’s known to disrupt sleep.

Some people’s bodies clear out stimulants better than others’s, which allows them to take clen first thing in the morning and still sleep fine, but even they tend to experience sleep troubles at some point during a cycle.

Considering the fact that most of us don’t get enough sleep as it is, it goes without saying that taking drugs that further exacerbate this, like clen, is a poor decision for our overall health and wellbeing.

Clenbuterol Depletes the Body of Potassium

Evidence suggests that clenbuterol may cause the body to lose large amounts of potassium and taurine.

Potassium plays an important role in muscle contraction and heart function and taurine may help prevent muscle cramps, so this explains why clenbuterol is linked to heart abnormalities and muscle cramps.

Is Clenbuterol Legal?

Yes, clenbuterol is legal to purchase, sell, and own in the United States and most other countries.

The reason many people think otherwise is manufacturers aren’t allowed to include it in products that are meant for human consumption, like bodybuilding supplements.

That said, clenbuterol is banned in almost every organized sport because it may enhance athletic performance.

Most developed countries have also banned its use with livestock because it can find its way into the meat, which finds its way into you.

Example: that’s what happened a few years ago to soccer players participating in the Junior World Cup, which was held in Mexico.

The Bottom Line on Clenbuterol

Clenbuterol will help you lose fat faster, and while it probably won’t help you gain muscle, it’ll help you keep the muscle you have while dropping fat.

It’s legal to buy and easy to get, too, which has helped it become one of the most popular cutting drugs around.

That said, it’s not as effective as many drug pushers claim.

At best, you’re probably looking at a ~10% increase in your basal metabolic rate, which surely helps, but you could also just walk for an hour or so to achieve the same effect.

Furthermore, there’s a very good chance that clen is much worse for you than milder stimulants like caffeine and ephedrine.

We can’t say for sure, but evidence strongly suggests that it increases your risk of heart disease and dysfunction, and especially when doses get high.

It’s also easy to overdose and can even be lethal if taken in too large of amounts or for too long.


So, if you want a simple recommendation, it’s this:

Stay away from clenbuterol.

In my opinion, the risks far outweigh the benefits, and it’s just not necessary to build a muscular, lean, healthy body that you can be proud of.

What’s your take on clenbuterol? Have anything else you’d like to share? Let me know in the comments below!