Clenbuterol – Everything You Need to Know

Last Updated: July 30, 2022


What if there was a way to increase your oxygen intake during exercise, improve energy levels, and boost your metabolism, all with a safe, widely tested medication sold legally in dozens of countries around the world?

With , it’s possible to see proven gains in all aspects of your fitness, and all without using risky supplements with suspicious ingredients.

Clenbuterol is a bronchodilator and decongestant medication originally intended to address patients with asthma and other pulmonary conditions.

For years, it was used in the U.S. livestock market to produce animals with more muscle and less fat, and is still used today in human treatments in countries across Europe and Latin America.

The unique combination of functions – the decongestant components reduce blood pressure while the bronchodilator capabilities widen blood vessels to increase oxygen levels in the blood – offers incredible possibilities for those seeking more effective workouts and an improvement to physical health.

While unapproved by the FDA for medical use in the United States and seen as controversial due to its use in bodybuilding and dieting, clenbuterol has amazing potential to revolutionize your workout routines and help you look and feel better than ever.

What is Clenbuterol?

what is clenbuterol

Also known as Dilaterol, Spiropent, and Ventipulmin (as well as the slang name “clen“), clenbuterol is a sympathomimetic amine that functions as a bronchodilator and decongestant.

When prescribed by a doctor, it is used to help those with asthma breathe easier.

Clenbuterol is also a beta-2-agonist, promoting the production of epinephrine and noradrenaline in the body for increased energy and a heightened metabolism.

When combined with the effects on respiration and blood oxygenation, this effectively creates a positive environment for both improved performance during physical activity and higher rates of fat burn.

The Legality of Clenbuterol

Currently, clenbuterol has not been approved by the FDA and cannot be prescribed by doctors for medical treatment.

There are several theories behind this; most likely, it has never been evaluated or approved due to its similarities to other existing medications, eliminating a need for it on the market.

However, it is currently approved for use in horses and thus can still be purchased within the U.S.

Outside the U.S., it is widely used in legitimate medical treatments and is available in both tablet and liquid preparations.

According to the Drug Enforcement Administration, clenbuterol is not considered a controlled substance and is not included in the Controlled Substance Act.

As such, there are no legal penalties for purchasing or owning this substance.

Is clenbuterol legal

Photo: Flickr

Professional athletes should be aware that Clen is considered to be a performance enhancing drug by the World Anti-Doping Agency and the International Olympic Committee.

How Does it Work?

Clenbuterol provides desirable results as both a bronchodilator and thermogenic medication. In simple terms, this means that it both improves the ability to breathe and raises body temperature for a heightened metabolism.

As stated above, clenbuterol is a beta-2 agonist.

As a beta-2-agonist, it stimulates the sympathomimetic nervous system or, more specifically, the beta-2 receptors throughout the body.

This function drives the reduction of airway obstruction, but also raises the body temperature of the individual to increase metabolic rate.

This rise in temperature is caused by increased production by the mitochondria in affected cells, which results in more calories burned during normal daily life.

Anecdotally, clenbuterol also reduces appetite. As most trying to lose weight are well aware, weight loss only occurs when calorie output exceeds calorie intake.

By reducing appetite while improving metabolic rate, weight loss becomes much easier.

Some regular users report losing 10 to 20 pounds of fat in the first month of use.

Clenbuterol also has purported anabolic properties, but this has not yet been proved.

Lab tests on rats have shown a demonstrated increased anabolic activity, but there appears to be little effect in humans.


Clenbuterol has many benefits to users, particularly those seeking to increase VO2 max and improve muscle-building results.

The effects of taking Clen can include:

  • Functions as both a bronchodilator and decongestant; this both widens blood vessels and lowers blood pressure, increasing oxygen levels in the blood when in use
  • Thermogenic abilities, boosting activity in the mitochondria that raises body temperature .5 to 1 degree, improving metabolism
  • Easier breathing for users with pulmonary challenges
  • Increased strength, performance, and endurance
  • Improved energy and endurance due to heightened production of epinephrine and noradrenaline
  • Fat loss while preserving muscle tone
  • Appetite suppression capabilities, helping users to reduce cravings and unhealthy binges
  • Long-lasting results; metabolism-boosting benefits of clenbuterol can last for up to five weeks

For those who want to see weight loss with increases in muscle gain, clenbuterol can be an asset both in and out of the gym.

Side Effects

Side Effects

As with most medications, there may be side effects that accompany clenbuterol’s use.

These are primarily associated with the stimulant properties of the drug and may be dangerous when not handled appropriately.

Jitters and Anxiety

Many stimulants can cause anxiety and irritation, similar to drinking too many cups of coffee.

When clenbuterol is consumed in excessive dosages, it can cause a wired feeling and jitters.

This sensation may go away in time, or may persist throughout use. Sweaty hands and shaking may also occur.


Also known as high blood pressure, clenbuterol can cause hypertension after prolonged use.

When severe, hypertension can cause heart attack, stroke, and kidney damage.

Always monitor blood pressure when using this or any other workout supplement.

Increased Heart Rate

While an elevated heart rate is desired throughout exercise to improve cardiovascular health, it can be quite dangerous when sustained over a prolonged period of time.

Be sure to monitor heart rate when using clenbuterol both before, during, and after exercise.

Cardiac Hypertrophy

Cardiac hypertrophy is arguably the most serious potential side effect of clenbuterol.

Also known as a thickening of the heart muscle, cardiac hypertrophy decreases the size of the chambers of the heart.

This can cause complications like strokes, reduced supply of oxygen to the heart, and loss of heart function.

Users who experience chest pain, a rapid or fluttering heartbeat, shortness of breath, and fainting after exercise should seek medical attention to rule out serious issues.

Muscle Cramps

Cramping is a common side effect with clenbuterol.

This is often related to the increased physical exertion that accompanies use.

To avoid muscle cramps that may reduce the ability to exercise, drink plenty of water to stay properly hydrated.

Some users also find relief in taurine supplementation, as using clen can decrease natural taurine production in the body.

Trouble Sleeping

Stimulants like clenbuterol can elevate functions in the body, including brain activity that may make sleeping challenging.

With a half-life of 34 hours, clenbuterol can stay in the body longer than most medications, leading to results that may extend overnight and into the next day.

As with the use of any supplementation, be sure to speak with your doctor if you notice any side effects that seem unusual or atypical, or are causing discomfort.

Dosage and Usage


Unlike some supplements that are made up of largely natural ingredients, clenbuterol is a prescription medication that should only be taken as directed.

Due to the nature of clenbuterol and the potential side effects, users should not take extra doses in anticipation of additional enhancements; exceeding recommended quantities increases the likelihood of more dangerous complications.

In a medical setting, most patients begin taking 20 mcg per day.

For those with severe pulmonary conditions or who have been on the medication for a prolonged period of time, 40 mcg per day may be required.

As those who take clen recreationally for its fitness and weight loss benefits do not have a doctor’s guidance when taking doses, it’s important to measure carefully and follow best practices.

Most men taking clenbuterol will find an initial dose of 40 mcg to be sufficient, while women may prefer to start with 20 mcg.

Doses may need to be increased over time to see continued effects, but this process should be done carefully and slowly to reduce the likelihood of side effects.

For most effective results, regular users suggest cycling doses on a set schedule.

How to Cycle

In a two-week cycle, users take clenbuterol for two weeks straight, once daily, and then take two full weeks off.

This provides ample time to get the body used to regular doses in order to see best results.

Those serious about weight loss often scale up and down during this time; in the first week, users begin with 40 mcg and scale up by 20 mcg each day.

At the end of the first week, they scale back down, ending the last day of the cycle back at 40 mcg again.

Then, no supplementation is consumed during the following two weeks.

At the conclusion of 14 days off, the cycle begins again.

Some users don’t like this method as it leaves two full weeks in which progress can’t be seen.

This can be problematic for those used to the effects; without a reduced metabolism and the benefit of an appetite suppressant, users may have trouble maintaining good habits, leading to weight regain.

Four Day Cycle

A four-day cycle is similar to a two-week cycle; users take clenbuterol for four days, then take four days off.

This may be preferred due to the shortened period of disuse.

Four-day cycles generally do not include scaling up and down in dosage either, as there isn’t enough time to build up to a high dose.

However, some users dislike shorter cycles as they don’t allow significant time on the medication, potentially limiting results.

16 Week Cycle

A 16-week cycle is the longest recommended cycle for users, with 16 weeks of continuous use that gradually scales up in dose.

This cycle is encouraged for men only, and generally uses the following ladder:

  • Week 1: 40 mcg
  • Week 2: 40 mcg
  • Week 3: 60 mcg
  • Week 4: 60 mcg
  • Week 5: 60 mcg
  • Week 6: 80 mcg
  • Week 7: 80 mcg
  • Week 8: 80 mcg
  • Week 9: 100 mcg
  • Week 10: 100 mcg
  • Week 11: 100 mcg
  • Week 12: 120 mcg
  • Week 13: 120 mcg
  • Week 14: 140 mcg
  • Week 15: 140 mcg
  • Week 16: 140 mcg

After 16 weeks, users should take a full 16 weeks off. This program is best for those who have goals they wish to achieve and, with hard work and effort, are able to reach objectives in a four-month time frame.

Some users may consider not returning to a scheduled cycle at all, assuming sustaining target weight and muscle mass is possible.

Women are encouraged to keep cycles to 12 weeks at most, with a maximum dose of 100 mcg.

Continuous Use

For those uninterested in cycling or who are uncomfortable with taking time off of clenbuterol when attempting to reach goals, continuous use is an option.

Similar to a 16-week cycle, users may need to scale upwards as time progresses to see best results.

Unlike a 16-week cycle, however, users should cease taking clenbuterol whenever goals are met, not necessarily at the end of a four-month period.

Clenbuterol should not be used in high quantities indefinitely due to the potential health risks, so cycling is often encouraged, especially for those interested in ongoing gains.


Here’s a few examples of the type of results some guys have gotten from using clenbuterol.

While everyone’s body chemistry is unique and individual results will tend to vary, these images do show some fairly typical results.

Clenbuterol - Everything You Need to Know 7

Clenbuterol - Everything You Need to Know 8

Clenbuterol - Everything You Need to Know 9

Clenbuterol - Everything You Need to Know 10

Clenbuterol - Everything You Need to Know 11

Video Review


Clenbuterol Alternatives

For those looking for safer alternatives to clenbuterol that are 100% legal, there are several over-the-counter supplements that aim to mimic the effects of the drug without the negative downsides.

Some of the better brands include:

Clenbuterol - Everything You Need to Know 12If you’re looking for a great Clen alternative, I recommend Clenbutrol by CrazyBulk.

To learn more, check out my review here…

It should be noted that even though these products are legal and safe when taken as directed, you should still exercise caution if you decide to use them.

If you have any pre-existing medical conditions, or other health concerns about using these types of supplements, talk to a doctor first.


As a highly used medication in many parts of the world, clenbuterol is safe for human consumption and offers many advantages not available in over-the-counter supplementation.

A drug that both improves blood oxygen levels and boosts metabolism, clenbuterol provides a unique opportunity to lose weight, feel great, and finally achieve the body of your dreams.

That said, Clenbuterol isn’t right for everyone, but for those who want a safe, tested way to lose weight and improve gains, it may be a wise decision.

Those considering clenbuterol regimens are encouraged to do as much research as possible, review all pros and cons, and put a reliable plan in place to avoid the chance of any side effects.

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