Clenbuterol is a fat-burning drug that raises your metabolic rate. Even though it is not approved for use, some athletes and bodybuilders use clenbuterol to help them reach their fitness goals.‌

Here’s what you need to know about this powerful and risky medication.

What Is Clenbuterol?

Clenbuterol is a drug that is not approved for human use in the U.S. In some countries, it is available by prescription only for people with asthma or other breathing problems. Since 1998, the FDA has allowed clenbuterol for treating horses with asthma. It is not allowed for animals that are used in food production.‌

Clenbuterol is a substance that has steroid-like effects and is classified as a beta2-adrenergic agonist. This means that it stimulates the beta2-adrenergic receptors in your throat. The medicine helps relax your muscles and lungs, making it easier to breathe if you have asthma or another respiratory condition. It can stay in your body for up to 39 hours after you take it.

Used

Clenbuterol’s initial use was as an asthma drug. However, bodybuilders, performance athletes, and those wanting to lose weight are now using the drug.

Clenbuterol can be used as a weight-loss aid because it can increase a person’s metabolism. As well as reducing body fat and weight, it also allows the user to retain both muscle mass and body strength at the same time.

Clenbuterol became known as a celebrity diet secret because of its apparent use by celebrities and famous athletes.

Clenbuterol for Bodybuilding

However, clenbuterol — also called clen — is abused by athletes and bodybuilders for its ability to burn fat. The same receptors that are activated when taking clenbuterol for asthma also help to burn off fat and increase lean muscle mass. Athletes who use clenbuterol daily typically take 60 to 120 milligrams per day. Normally this is taken in combination with other performance-enhancing drugs or anabolic steroids.‌

Clenbuterol increases your body temperature through a process called thermogenesis. Once your body temp is up, your metabolism is then primed to burn off more calories. Since fat is stored in the body as energy, your body can use the calories that you already have stored. This can decrease your body fat and lower your overall weight.‌

Because clenbuterol is a bronchodilator, it opens up your airways when you take it. This is helpful for those with asthma. For athletes, this allows them to increase their stamina by having more airflow moving around the body. More oxygen is available, so you can perform harder and better. ‌

Even though it isn’t legal in the US, athletes and bodybuilders continue to abuse clen to help them cut weight and increase muscle mass. Many see it as an alternative to anabolic steroids — the drugs that typically come to mind when you think of performance-enhancing substances. It has the reputation of being a “non-steroidal steroid” due to its ability to mimic steroids. Since it isn’t technically a steroid, some athletes saw clenbuterol for bodybuilding as a more “natural” approach to building muscle.

Dosage

Athletes and bodybuilders taking clenbuterol will often work on a program cycle that includes on and off periods.

Such a program could mean 2 days taking clenbuterol and 2 days without taking any, or perhaps a week taking the drug followed by a week of none.

Dosage can vary, depending on factors that include gender and tolerance, and it can be taken orally or injected.

Both methods have risks. Injections can cause scarring or air bubbles to form in the blood, while tablets can affect the liver.

When used in Europe and Latin America to open up the airways in cases of asthma, the recommended dose is 0.02–0.04 milligrams (mg) per day.

Risks and side effects

The reason clenbuterol is banned in so many countries and has become so controversial is that many side effects are associated with it.

Many of the side effects are the same as those associated with amphetamines, including:

• anxiety
• shaking
• headaches
• abnormal sweating
• raised body temperature

Clenbuterol can also have negative effectsTrusted Source on the heart, such as heart palpitations, atrial fibrillation or an irregular and often fast heartbeat, and problems with blood pressure.

Increased heart rate and dilation caused by the drug can lead to what is known as cardiac hypertrophy. This condition is when the heart grows to an abnormal size, which in turn can lead to a heart attack and eventually death.

Also, clenbuterol contains dopamine, which is commonly known as the reward hormone. Dopamine is closely associated with addiction. As such, clenbuterol can be highly addictive.

In many countries, clenbuterol is banned from being used in animals that will be consumed by humans.

Clenbuterol can reduce the amount of potassium naturally occurring in the body. Consequently, those taking it as a drug will often also eat an increased amount of bananas to replace the potassium.

Athletes will often accompany the taking of clenbuterol alongside a diet that is high in protein, moderate in carbohydrates, and low in fat.

Some of the most common side effects include:

• Heart palpitations
• Tremors
• Increased heart rate (tachycardia)
• Lowered blood potassium (hypokalemia)
• High blood sugar (hyperglycemia)
• Anxiety 
• Agitation
• Sweating 
• Cardiac arrest
• Feeling hot or warm
• Insomnia
• Muscle cramps

You are more likely to have these side effects if you take higher doses of clenbuterol to achieve its weight loss effects. Since this drug stays in your body for quite a while, you could have side effects anywhere from one to eight days. Studies show that more than 80% of people abusing clenbuterol who had serious side effects had to be hospitalized.

Outlook

The effects that clenbuterol can have on the heart and muscles will depend on how high a dose someone has been taking and for how long. The risks increase with the dose and duration.

Those taking high doses can experience long-term side effects quickly, such as a decrease in the size, weight, strength, and activity of the heart.

Clenbuterol is illegal for human consumption in the U.S. for a good reason, and anyone buying the drug online should be extremely cautious.

While some may choose to take the risk because of the less harmful side effects, they should always remember the potentially extreme side effects as well.