Clenbuterol Side Effects

By: Juice

Last updated: is intended for informational purposes only and does not take the place of professional medical advice.

When it comes to bodybuilding and physique competitions, Clenbuterol (Clen) has become one of the most desirable drug to use during contest preparation where fast and efficient fat burning is the main goal to achieve the most chiselled, defined physique possible.

Clenbuterol Side Effects
Clenbuterol Side Effects

Clen comes with two big benefits for performance use, but by far the most desirable and significant benefit of Clen that draws people to use it is its fat burning effects. A distant second is its ability to enhance cardiovascular performance.

If you’re looking for powerful fat burning drugs to speed up and enhance your results, is Clenbuterol a compound you should consider? Or is it far too dangerous to use? With so many celebrities using Clenbuterol, surely it must be the best choice for losing weight fast? These are the questions we ask when considering if Clenbuterol is both safe and effective to use to burn fat.

But Clenbuterol’s long list of potential side effects is likely to make you stop and think whether this is a drug you want to risk taking, despite the obvious benefits.

Author’s Note: The following guide is based on my personal experience and does NOT promote the use of illegal steroids (PEDs).

What is Clenbuterol (Clen)?

Clenbuterol is often used by steroid users, and used alongside anabolic steroids in stack; but Clen itself is not a steroid. It is a medication that acts as a stimulant of the sympathetic nervous system.

Clenbuterol Structure
Clenbuterol Structure

It used as a decongestant and bronchodilator for people who are suffering with breathing related conditions like asthma. It is also classed as thermogenic drug (increases heat through stimulating the metabolism), and it’s this particular property that has made Clenbuterol appealing to people wanting to lose weight – even though weight loss is not an intended or approved use of this drug.

Clenbuterol has become famous as a fat loss agent due to its use and promotion by some of the biggest female celebrities in the world. Other people raise the alarm about this potentially dangerous use, particularly with some celebrities promoting an extremely thin and unhealthy physique, and the possible health impacts of using a powerful drug like Clen for a purpose it wasn’t designed for.

Despite the risks, Clenbuterol cycles continue to be a popular choice in the bodybuilding world for the purpose of cutting where it’s often used in combination with fat burning steroids and other non-steroid compounds.

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What does Clenbuterol do?

As a treatment for chronic asthma and other similar conditions affecting breathing, Clenbuterol works exceptionally well as a bronchodilator where it quickly and effectively aids in muscle relaxation of the airway so the airway is open and normal breathing can take place.

Clen is also considered a decongestant for medical use where it can constrict and narrow blood vessels to minimize congestion. By understanding these medical uses of Clenbuterol (where it is only used in some countries outside the US), we get an initial understanding of what Clen can do for performance users.

What Clenbuterol’s medical applications don’t tell us is the main reason bodybuilders and competitors want to use this drug: for fat loss. Clenbuterol has a very powerful effect on the metabolism and this is the core reason why it is so highly valued as a fat burner drug, even though it has no medical approval anywhere in the world for weight loss purposes.

Through stimulation of Beta-2 receptors, Clenbuterol boosts your metabolic rate. Thermogenesis is the key process in this, which is simple an increase of the body temperature as a result of an escalation of cell heating.

As the cells are producing more heat, this heat is released from the cells and that results in a higher body temperature and a faster and more efficient metabolism that burns body fat as energy quicker.

Clen can cause the metabolism to be running at an increased rate for up to five weeks or so, even if you aren’t physically feeling the effects of it. This can commonly lead to people thinking it’s not working, but your results will tell you otherwise (as long as you continue with your fat loss diet and training).

After around five weeks Clen’s effectiveness can start to decrease as your body adapts to it. This timing is going to be different for each individual but most users will find that by the five week mark you’ll want to be considering your dose if you plan to continue use of Clen and if you haven’t yet reached your maximum dosage.

A bonus and not often talked about benefit (for those dieting, at least) of Clenbuterol is its appetite suppressive properties. A suppression of your appetite is going to assist monumentally while dieting to cut off stubborn fat for a competition – if you’re feeling hungry less often, you are simply going to have an easier time preventing over eating or eating the wrong types of foods.

Perhaps one of the reason that appetite reduction is not a widely spoken of benefit of Clen is because not everyone will experience this effect. Some users will feel no change whatsoever in their appetite, while others will find a sudden reduction.

Unfortunately there is no possible way to predict which category you will fall into until you start using Clenbuterol. Appetite suppression is an effect that is not thought to have a middle ground. You will most likely either experience it fully, or not at all.

What about lean muscle growth? This is an often touted benefit of Clenbuterol. It’s true that Clen can promote some growth of lean mass, but it is far from a muscle building compound. Those who have used steroids for bulking previously will likely find Clen’s muscle growth effects to be almost non-existent.

For users who are not used to using muscle gain compounds, and for women, Clenbuterol can provide a small but noticeable increase in lean muscle which will be welcomed as a boost to the defined and toned physique that develops as more body fat is shed.

Naturally, to be gaining muscle you will need to be providing your body with the required calories. Clenbuterol does have some effect on protein synthesis and this gives it some mild anabolic effects, but those on extreme calorie deficit cutting diets (which is common when using Clenbuterol) will struggle to gain any mass at all.

Another benefit of Clenbuterol’s (mild) anabolic effect is that it makes it easier to retain muscle while cutting. Muscle loss or catabolism is a battle you face when eating at a calorie deficit with the goal of burning fat.

This is why steroid users will almost always want to include a compound that promotes muscle retention by boosting anabolic activity, maintaining a positive nitrogen balance and preventing catabolic effects.

Clen is not hugely powerful in this regard, and many male users will use it alongside anabolic steroids for this purpose.

Short-Term Clenbuterol Side Effects

The fact that Clenbuterol is a stimulant means you can expect a range of side effects that will impact every individually to a different extent. Some users of Clen will be significantly more sensitive to stimulant caused side effects, while others will have a higher level of tolerance. You simply won’t know what negative effects you can expect from Clenbuterol until you’ve used it yourself.

We can still get an overall idea of all the possible side effects which have been reported from those who have used Clen for bodybuilding and competition purposes.

If you’re already an anabolic steroid user, you can expect Clen side effects to be very different to what you’re used to with steroids. Clen is a completely different type of compound and so it acts in a very different way to steroid hormones.

Stimulant type short term side effects of Clenbuterol can include:

  • Shakiness and tremors
  • Racing heart and heart palpitations
  • Increased perspiration
  • Increased anxiety
  • Difficulty sleeping

These side effects, while relatively minor compared to those of anabolic steroids, are caused by Clen’s sudden stimulation of the nervous system and can look very similar to those experienced by some people who consume common everyday stimulants like caffeine in high quantities.

Most Clen users will find these side effects come on soon after starting Clenbuterol and as your body gets more accustomed to the drug they can reduce or even stop altogether.

In other users, these short term side effects will be difficult to tolerate to the point that you might choose not to use Clenbuterol at all. Those suffering with existing anxiety should keep in mind the potential effects on mental health as well as physical.

It’s important to realize that even if the above effects fade away, Clenbuterol’s fat burning ability caused by an enhanced metabolism is still going on.

A lack of stimulant side effects does not mean that Clenbuterol isn’t working, and shouldn’t be taken as an indication that you need a higher dose if your dosage has reached the maximum level of your intended incremental dosage plan.

Other short term side effects besides those normally associated with powerful stimulants can include:

  • Headaches
  • Muscle cramps

Cramps can be mitigated to some extent by drinking more water and keeping up your electrolyte nutrient intake (particularly potassium, sodium, calcium, and magnesium). Staying hydrated can also assist with some headaches but each user will find their response to be different. Usually these side effects will subside as soon as two days after starting Clenbuterol, but in some cases can extend up to one week.

Long-Term Clenbuterol Side Effects

Ongoing insomnia can also become a longer term side effect of Clen. In the worst case, some people can find themselves virtually unable to go to sleep and this isn’t helped by Clen’s half life which stretches to almost 36 hours, making it difficult to time your doses to avoid sleeping difficulty. Lack of sleep will impact your results negatively and make it harder for you to recover from intensive workouts.

More serious long term side effects can impact heart function. The heart can suffer within a surprisingly short time if you are using Clenbuterol at high doses. These damaging impacts can include changes to the size and weight of your heart, less heart strength, and overall heart activity being compromised.

Due to the more rapid heart rate and increased dilation that Clen produces, in the most serious cases you could experience cardiac hypertrophy where the ventricle walls thicken due to the stress that Clenbuterol puts on the heart. The result? A potential heart attack and possible death.

Needless to say, using Clenbuterol at high doses is a serious health risk and should be avoided at all costs. But even at lower doses, some unlucky users of Clenbuterol can find themselves experiencing some very alarming heart related side effects which can quickly turn into long term and lifelong side effects.

There’s no real way of knowing your individual risk of heart related impacts when using Clenbuterol as even those with a healthy heart can wind up with serious issues.

Women Specific Side Effects

Women will normally want to take a Clenbuterol dosage that is lower than the average male dose. This does not remove the risk of side effects at all though.

Most side effects that females risk experiencing with Clenbuterol will be the same as men, including all the adverse effects described above like increased heart rate, sleeping difficulties, muscular cramps and increased perspiration.

These are quite mild effects which most women will find reduce after the first couple of weeks using Clenbuterol.

There are some possible additional very serious complications that are female specific though. Women using Clenbuterol run the risk of disrupting the menstrual cycle and fertility complications.

When a female takes Clenbuterol at high doses for prolonged periods of time, the danger of these life changing side effects developing will increase. This is an important reason why it’s critical that women keep their Clenbuterol dosage as low as possible.

Unfortunately, if side effects relating to menstruation and fertility do develop, they can continue to be a problem even after you’ve stopped taking Clen.

Clenbuterol has not been studied in depth for its effects and risks in humans at performance doses, so the exact cause of these serious complications is not well understood.

Additionally, breastfeeding and pregnant women should avoid any use of Clenbuterol. The potential impacts that Clen could cause to a developing baby are not understood, and this alone makes the risk of using this very powerful stimulant far too high for females who are pregnant or nursing.

Is Clenbuterol Safe?

Using any drug outside of its approved medical use always comes with great risks. Clenbuterol is no exception and some users will simply find the stimulant side effects themselves are too difficult to handle.

If you’re someone who struggles with a few cups of coffee daily, Clen can present much greater challenges. These are considered mostly annoying side effects, however those with mental health conditions can find the extra anxiety and potential associated depression that may develop after “coming down” off Clen is too dangerous.

Prolong used at higher doses can take Clenbuterol’s safety to all new levels and this is where the risks will amplify considerably. Heart palpitations, chest pain and rapid breathing can bring about fear of a heart attack. In the most severe circumstance, an actual heart attack is not unheard of after using Clenbuterol.

One of the reasons Clenbuterol is not approved for use in the USA is due to its potential to cause permanent organ damage. Studies have found that a very high percentage of Clenbuterol users who experienced serious side effects ended up having to be admitted to hospital.

Many of these people are first time users of Clenbuterol, and it is known that those who are using Clen for the first time are more likely to suffer with side effects.

This means when you decide to use Clenbuterol for the first time you are statistically likely to experience one or more alarming side effects because you have no way of predicting just how your body will respond to Clenbuterol.


What is Clenbuterol used for?

First and foremost, Clenbuterol is a bronchodilator that is very effective in helping people suffering with breathing difficulties. Despite this, it does not have approval by the FDA for medical use in the US. It is approved in many other countries though. Bodybuilders and physique models often use Clen to aid in fast fat loss due to its thermogenic properties.

Clen is approved for medical use in many countries, but not in the US as there are other similar bronchodilator medications already approved.

Clenbuterol is not approved anywhere for the purpose of weight loss or for any use besides for bronchial dilation. This means when using Clen for any other purpose, it is considered illegal.

Clenbuterol is listed as a banned substance by both the World Anti-Doping Agency and the International Olympic Committee due to its performance enhancing effects.

Where can I buy Clenbuterol?

Because Clen isn’t approved or used in the US for any purpose, American users will buy Clenbuterol from other countries where it may be obtained through the pharmaceutical system as it is prescribed to treat asthma. As Clenbuterol is not legal in the USA it is against the law to import it and serious fines can apply.

What does Clenbuterol do for men?

Clenbuterol is effective at both burning fat and increasing muscle mass in men. Clen is not a powerful muscle builder like steroids, so men will usually use it along with anabolic steroids.

Clenbuterol has the same effects for men as for women: fat loss and increased stamina and endurance caused by the increased air flow as a result of enhanced airway opening.

Can Clenbuterol be taken safely?

There’s always a health risk when using Clen for weight loss and fitness. The higher doses can potentially lead to long term damage coming on quite quickly and this can include reduction and size and efficiency of the heart, high blood pressure, anxiety and depression.

Can Clenbuterol affect mental health?

Clenbuterol can have mental health impacts such as increasing anxiety, bringing on depression particularly when the drug stops having effect, and through the possible sleep problems that Clenbuterol can cause, which in itself can also lead to increased anxiety, moodiness and a range of other mental and physical health problems.

Final Thoughts

Clenbuterol is certainly capable of helping you achieve an amazing physique. But is it worth it considering those scary side effects that include the possibility of serious heart damage and even heart attack?

If you use Clen at too high of a dose or for too long, a very long list of side effects can develop. Some of these will also occur even at low doses.

The potential adverse effects of Clenbuterol include tremors, dizziness, muscle cramps, anxiety, chest pain, excess sweating, rapid heart rate and breathing, heart palpitations, increased body temperature, sleep difficulty and insomnia, high blood pressure and in the worst cases after long term high dosage use: cardiac arrest or heart failure.

About the Author
Juice Lewis, Author of
Juice Lewis

Real-life Experience, not Theory

I don't claim to know everything; what I talk about here is something I've done. From anabolic steroids to HGH, to peptides, insulin, and supplements, I've done it at some point in my life, and I can relate.