What is Clenbuterol? (Everything You Need To Know)

Benedict Ang, CPT, PN1-NC
Published by Benedict Ang, CPT, PN1-NC | Staff Writer & Senior Coach
Last updated: December 8, 2023
Our content is meticulously researched and reviewed by an expert team of fact checkers and medical professionals. They ensure accuracy, relevance, and timeliness using the latest reputable sources, which are cited within the text and listed at the end of the article. Before publication and upon significant updates, we confirm factual accuracy, committed to providing readers with well-informed content. Learn more.

With almost a decade of being in the fitness industry, I've worked with athletes and bodybuilders who asked about and who actually used clenbuterol to lose excess fat and increase lean muscle mass.

However, because I know that this performance-enhancing drug is a banned substance, I conducted extensive research and gathered as much feedback as I could from people who used it to determine its safety and efficacy, so I can advise my clients accordingly.

After five weeks of research, I’ve compiled my data in this article so both you and my clients can make an informed decision and be aware of all potential risks and benefits.

Let's begin.

Quick Summary

  • Clenbuterol aids individuals with bronchial asthma by increasing lung airflow and relaxing muscles, and it may also enhance athletic performance by boosting metabolism and muscle mass growth.
  • The drug is used by some athletes and bodybuilders to improve stamina and muscle recovery after intense workouts, though it's not legal for human use in the U.S.
  • A study from the National Library of Medicine indicates that Clenbuterol users may experience increased blood flow and muscle oxygenation, aiding in muscle recovery and growth.
  • In my opinion, I advise prioritizing sustainable weight loss and muscle building through balanced nutrition and lifestyle changes over relying on Clenbuterol.

What Does Clenbuterol Do?

Spilled white pills top view

According to the National Institute of Health (NIH), Clenbuterol, commonly used for bronchial asthma, can ease breathing by relaxing lung muscles and increasing airflow, which improves oxygen circulation [1].

It's known that some athletes and bodybuilders use it to boost stamina and muscle recovery after intense workouts, thanks to its role in enhancing muscle oxygenation.

However, it's important to note that in the U.S., Clenbuterol is not legal for human use, as per FDA regulations [2].

According to NIH, it's observed that numerous sports enthusiasts continue to use it for weight loss and performance enhancement [3].

How Does It Enhance Athletic Performance?

In my experience as a fitness trainer, I've observed that Clenbuterol can significantly enhance athletic performance by boosting metabolism, sharpening mental focus, and increasing muscle mass.

However, its overuse can lead to it becoming a powerful performance enhancer and fat burner.

This according to NIH, is due to its thermogenic quality, which raises body heat and, in turn, accelerates the metabolic rate [4]. A faster metabolism effectively burns off extra calories and fats, allowing for more vigorous and prolonged training sessions.

A study from the National Library of Medicine shows that those using Clenbuterol may notice an increase in blood flow and muscle oxygenation, which speeds up the delivery of nutrients, aiding in muscle recovery and growth [5].

Are There Risks Associated with Taking Clenbuterol?

Man wearing sleeves holding his chest with both hands

I must emphasize that Clenbuterol poses serious health risks, which is why it's banned in several countries, including the U.S.

Particularly for beginners or those combining it with steroids or performance enhancers, misusing Clenbuterol can lead to grave health issues.

Going beyond the recommended dosage and usage period can result in a range of health complications, such as:

Hypokalemia or Lowered Blood Potassium

According to research by NIH, acute clenbuterol overdose resulting in low serum potassium concentrations occurs when this substance stimulates the adrenergic nervous system (ANS), allowing extracellular potassium to enter cells [6].

"Having the right amount of potassium is critical for the heart to beat properly. If your potassium levels are too high or too low, the heart is at increased risk of a cardiac arrest."

- John Day, MD, Cardiologist, Intermountain Medical Center Heart Institute

Tachycardia or Increased Heart Rate

Heart rate increased concept

Research by NIH suggests that using clenbuterol in high doses may cause prolonged tachycardia or rapid heart rate, atrial fibrillation, and abnormal blood pressure [7].

These cardiovascular side effects can lead to heart enlargement, or cardiac hypertrophy, which raises the risk of a heart attack and stroke.

Tremors and Anxiety

One study from ScienceDirect reveals that consuming higher doses of clenbuterol stimulates the central nervous system (CNS) and causes neurological symptoms such as muscle tremors, anxiety, agitation, and insomnia [8].

Furthermore, severe drug toxicity can cause seizures and psychosis in some people.

Hyperglycemia or Elevated Blood Glucose

Using clenbuterol continuously may result in high levels of glucose in the blood.

Also, people with high blood sugar may experience symptoms of abnormal sweating and feel warmer than usual.

Low Bone Mineral Density (BMD)

Research BY NIH also found that treatment with clenbuterol affects bone metabolism and increases bone resorption, or the destruction of bone tissues, leading to a decrease in bone mineral density and bone loss [9].

Nutrition, Lifestyle and Clenbuterol

Rather than relying on Clenbuterol, prioritize sustainable weight loss or muscle building through balanced nutrition and lifestyle changes.

  • Adopt a nutrient-dense, calorie-controlled diet rich in lean proteins, fruits, vegetables, and whole grains.
  • Incorporate regular exercise, combining cardiovascular workouts and strength training for optimal results.
  • Emphasize high-intensity interval training (HIIT) to boost metabolism.
  • Adequate sleep and stress management are crucial.
  • Instead of Clenbuterol, consider natural supplements like caffeine, green tea extract, or branched-chain amino acids, but consult with a healthcare professional before use.

Focus on a holistic approach, as long-term success lies in gradual, healthy transformations rather than quick fixes with potential side effects.

Is Clenbuterol Banned In Sports?

Close up image of white circular pills

I'm aware that Clenbuterol is completely banned in sports by both the World Anti-Doping Agency (WADA) and the International Olympic Committee (IOC), applicable at all times, in and out of competitions.

Despite this, it's no secret that some athletes still risk using it, probably for its fat-burning, muscle-building, and performance-boosting benefits, even though it carries significant health risks.

However, it's crucial to remember that as a drug prohibited by WADA and the IOC, athletes testing positive for Clenbuterol could be banned from their sport.

Comparison with Other Performance Enhancers

Compared to other common fat burners like caffeine or green tea extract, Clenbuterol is more potent but carries greater risks, including cardiovascular issues and adverse side effects.

  • Unlike legal supplements, Clenbuterol's use is restricted due to safety concerns, with potential legal consequences.
  • While it may offer rapid results, its effectiveness comes with heightened health risks, making it a less advisable option.

Legal, well-researched alternatives focus on safety and sustainable outcomes, emphasizing exercise, balanced nutrition, and natural supplements for long-term health benefits.


Is Clenbuterol Available for Purchase?

Clenbuterol is only available for purchase in a few countries in Europe and Latin America, where it is legal for the treatment of asthma.

Most countries, including the US, do not yet permit its use as a medicine or sports supplement because it hasn't been proven safe for human use.

How Long Does Clenbuterol Stay in the System?

Clenbuterol can stay in the system for varying lengths of time, depending on the dosage and the user's reaction to the drug.

What Is the Safe Dosage of Clenbuterol?

The safe dosage of clenbuterol ranges between 0.02 and 0.04 milligrams per day, which is the recommended dose for treating asthma in several countries where the drug is approved for medical use. Also, the dosage can differ depending on the drug's use, gender, and tolerance.

How Does Clenbuterol Burn Fat?

Clenbuterol burns fat in two main ways, namely epinephrine receptor binding and speeding up an individual's metabolism rate. Clenbuterol targets the same receptors that react to the hormone epinephrine. And while this is a completely natural process in the human body, Clenbuterol does so much more effectively.


  1. https://pubmed.ncbi.nlm.nih.gov/3902376/
  2. https://www.deadiversion.usdoj.gov/drug_chem_info/clenbuterol.pdf
  3. https://pubmed.ncbi.nlm.nih.gov/7476054/
  4. https://pubmed.ncbi.nlm.nih.gov/31887249/
  5. https://pubmed.ncbi.nlm.nih.gov/3032321/
  6. https://pubmed.ncbi.nlm.nih.gov/11527226/
  7. https://pubmed.ncbi.nlm.nih.gov/18072161/
  8. https://www.sciencedirect.com/science/article/pii/S1878540913001011
  9. https://pubmed.ncbi.nlm.nih.gov/12433936/
Was this article helpful?

About The Author

Benedict Ang, CPT, PN1-NC
Staff Writer & Senior Coach
Benedict Ang, CPT, PN1-NC is an ex-National Soccer player turned MMA and Kickboxing champion, with ACE CPT and PN1-NC certifications. His advice is rooted in education and experience, ensuring that readers receive scientific and battle-tested insights. His mission is to empower his clients and readers to realize their potential and become the best versions of themselves.
Learn more about our editorial policy
Dr. Harshi Dhingra, MBBS, MD is a published peer-reviewed author and renowned physician from India with over a decade of experience. With her MBBS from Bharati Vidyapeeth and an MD from Rajiv Gandhi University, she actively ensures the accuracy of online dietary supplement and medical information by reviewing and fact-checking health publications.
Learn more about our editorial policy
Dr. Kristy June Dayanan, BS, MD is an author with a BS degree from University of the Philippines and an MD from University of Perpetual Help System. Her ability to simplify medical science complexities and dietary supplement jargon for the average reader makes her a valued medical fact checker and reviewer.
Learn more about our editorial policy

You May Also Like

Top view of woman choosing nootropics pill
By Dr. Harshi Dhingra, MBBS, MD 13 days ago
Are Nootropics Safe? (Everything You Need To Know)
Soft Vs Firm Fat Featured Image
By Lisa Lorraine Taylor, BSc, CPT 9 days ago
Soft Vs Firm Fat (Everything You Need To Know)
A fit person with loose pants holding a weighing scale
By Lisa Lorraine Taylor, BSc, CPT 4 months ago
How Does the Body Burn Fat? Everything You Need to Know
Rice scattered on wooden table
By James Cunningham, BSc, CPT 3 months ago
Is Rice Good for Abs? (Cutting for a Six-Pack)
Where Are Steroids Legal Featured Image
By Benedict Ang, CPT, PN1-NC 2 months ago
Where Are Steroids Legal? (Everything You Need To Know)
Muscular man behind woman flexing his muscles
By James Cunningham, BSc, CPT 1 month ago
What Is Protein Synthesis? (Everything You Need To Know)

Write a Reply or Comment

Your email address will not be published. Required fields are marked *

Our scoring system is the result of objective testing data and subjective expert analysis by a team of fitness coaches and medical experts. Our scoring factors are weighted based on importance. For more information, see our product review guidelines.