Clenbuterol is a type of medication that’s a selective beta-2 agonist/antagonist and bronchodilator. That means it relaxes the smooth muscle tissue that makes up the airways to allow for freer breathing.

The United States Food and Drug Administration has approved clenbuterol only for use by veterinarians, who may prescribe it to treat horses with obstructive pulmonary disease or other lung conditions.

Clenbuterol is a β2-adrenoceptor agonist and bronchodilator, formulated to treat various breathing disorders, such as: inflammatory airway disease (IAD) and recurrent airway obstruction (RAO).

Clenbuterol is an effective anti-asthma medication, having been an approved prescription drug for humans since 1977 in several countries (albeit not the US).

In research, clenbuterol has demonstrated strong anabolic effects in animals; significantly increasing skeletal muscle mass, whilst reducing fat.

This has led to bodybuilders purchasing clenbuterol on the black market and utilizing it in cutting cycles, alongside other fat-burning steroids.

Hollywood celebrities have also been known to cycle clenbuterol, in a bid to transform their bodies in a short space of time.

However, clenbuterol’s effects in humans are somewhat dissimilar to those in animals. Clenbuterol’s ability to burn fat is undisputed; however, its muscle-building effects in humans are questioned.

Some users report no anabolic effects from clenbuterol, whereas others are adamant about its ability to add lean muscle tissue.

The truth may lie somewhere in the middle, with clenbuterol having anabolic properties; although not to the degree of anabolic-androgenic steroids.

Thus, clenbuterol may help bodybuilders retain muscle when cutting, although significant increases in muscle size and strength are unlikely. This is therefore more of an anti-catabolic effect (rather than anabolic).

Clenbuterol is generally taken as an oral; however, it is also available as a syrup or injection.

Clenbuterol Dosage

A person’s dosage will depend on what they are using clenbuterol for.

For example, an asthmatic may take 2 x 20mcg pills per day.

Patients suffering more severely with respiratory issues may take 4 x 20mcg pills per day.

However, bodybuilders or anyone taking clenbuterol for weight loss purposes may take 6-8 pills per day (120-160mcg). Such dosages are well beyond the therapeutic range used in medicine, therefore more severe side effects are to be expected.

People often respond to potent stimulants differently, thus the dosage should be tailored to how sensitive a person is to the drug.

Unlike with anabolic steroids, the dosage of clenbuterol is the same for men and women. This is due to it affecting the CNS, rather than working on a hormonal level (where women having significantly less testosterone and thus need smaller doses of steroids to obtain the same level of results).

Users typically build up a tolerance to clenbuterol quickly; thus to prolong its positive effects, users often start on a lower dosage and increase it slowly every third day.

A person should only continue increasing the dosage until the maximum amount, if they are comfortable with the side effects.

One user may be able to finish a 30 day clenbuterol cycle, reaching a peak of 120mcg; whereas another user may report severe side effects on 80mcg/day (and have to cut their cycle short).

The reason why clenbuterol cycles typically do not last beyond 4-6 weeks is due to beta-receptor downregulation.

Thus, clenbuterol’s positive effects can only be experienced for a limited time, until the body successfully regulates its temperature back to normal; causing fat burning to come to a halt.

This is also why some users choose to cycle clenbuterol for 2 weeks on, followed by 2 weeks off; or 2 days on/2 days off.

2 Week On/Off Clenbuterol Cycle

As previously mentioned, a short clenbuterol cycle can be utilized to prevent the body from building up a tolerance to the drug, ensuring further fat loss in future cycles.

A 2 week cycle may also reduce cardiovascular strain, among other side effects.

In one journal, a healthy 25 year old man was rushed to the ER after taking 20mcg of clenbuterol. His heart rate reached 140 beats per minute, whilst also displaying labile blood pressure.

He experienced palpitations, nausea, chest pain, sweating and anxiety.

Interestingly, he had been taking the same dose for the last 3 weeks, with no adverse effects. This is a prime example of where a 2 week cycle may be more optimal for sensitive users.

A 2 week cycle will often start in the 20-40mcg range, with the dose increasing every 1 or 2 days, until a maximum dose is achieved (usually being 100mcg-140mcg).

Users will then have 2 weeks rest before cycling clenbuterol again. However, the second cycle begins with the maximum dose from the first cycle. Thus, if the first cycle finished on 100mcg per day, this would be taken for the entire 2 weeks in the second cycle.

Every follow up cycle from this point onwards, should then start at the maximum dose to continue making progress.

No Testosterone Suppression

One of the biggest drawbacks of anabolic steroids is the shutting down of natural testosterone production.

Typically after a steroid cycle, it can take several weeks or months for endogenous testosterone to return back to normal levels.

However, clenbuterol (unlike anabolic steroids) does not compromise your testosterone. Thus, no PCT is needed and you don’t need to worry about losing your results.

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.