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Clenbuterol can also have negative effects Trusted 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.

Sife Effects of Clenbuterol

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

In 1994, 140 people in Spain were hospitalized after eating meat tainted by clenbuterol. Similarly, in 2006, 336 people in China were poisoned after eating pork that contained it.

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.

Risks and Side Effects

Many athletes and bodybuilders use clenbuterol for its benefits — but there are several dangerous side effects to be aware of.

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.

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New users of clenbuterol are more likely to experience side effects than people who have previously taken it. If you experience any of these side effects after using clenbuterol, it’s important to immediately stop using it and to get help from a doctor.

Increased Heart Rate

Clenbuterol arouses the sympathetic nervous system, casing users’ resting heart rate to become excessively elevated.

Professor Lisa Nissen, head of the School of Clinical Sciences at Queensland University of Technology, states:

Dr Thomas O’Connor also has anecdotal evidence of clenbuterol contributing to heart rates of 180 beats per minute.

Clenbuterol-use can also lead to chronic atrial fibrillation, a form of irregular heartbeat; caused by permanent scarring to the heart.

Thus, clenbuterol is an especially dangerous drug for anyone with existing heart issues or high blood pressure.


Anxiety is a common side effect of taking clenbuterol, due to its tendency to shift a person into fight or flight mode. Excessive arousal of the central nervous system may cause a person to perceive every day situations as threats, negatively affecting their mental health.


A racing heart and palpitations may also trigger anxiety, as users may think they are having a heart attack.

Taking a sedative may help to calm the central nervous system and reduce anxiety levels. However, this may also counteract the thermogenic effect of clenbuterol; thus negatively affecting fat loss due to less adrenaline and heat production.

High levels of CNS stimulation are also linked to depression, due to the subsequent ‘come down’ effect. This is due to clenbuterol initially boosting dopamine levels in the brain; for them later to drop, as a person builds tolerance or comes off the drug.

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Shaking is also common when taking clenbuterol due to heightened adrenaline, which is particularly evident in the hands.


Insomnia is common among clenbuterol-users, due to an overly active nervous system, causing hyperactivity.

Some experts recommend taking clenbuterol earlier in the day to improve the chances of falling asleep at night, however clenbuterol has a very long half life of 35 hours. Thus, such a protocol is likely to be ineffective, with high amounts of clenbuterol still peaking in the blood stream.

It is worth noting that sleep deprivation may elevate cortisol levels, further increasing blood pressure and inhibiting fat burning.


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.