- Clenbuterol isn’t a steroid. It’s a beta-2 agonist, a bronchodilator used in horses and, in some countries, for asthma.
- It raises metabolism and fat burning modestly, but most of the effect fades within weeks as receptors adapt.
- Its main risks are to the heart: fast heart rate, palpitations, low potassium and, rarely, heart damage.
- It isn’t approved for human use in Canada and isn’t listed in the CDSA.
Clenbuterol, or “clen”, is one of the most popular cutting drugs, and one of the most likely to land someone in an emergency department. This guide explains what it is, what it actually does for fat loss, why its effects fade, and the risks.
What is clenbuterol?
Clenbuterol relaxes the airways by stimulating beta-2 adrenergic receptors. It’s licensed as a bronchodilator for horses, and for asthma in people in some countries, though not in Canada or the US. It’s banned in food-producing animals in most countries because residues in meat have caused poisonings, including Mexican soccer players who tested positive after eating contaminated beef in 2011.
How it affects fat and muscle
- Thermogenesis: it raises body temperature and energy expenditure
- Fat breakdown: beta-2 stimulation increases lipolysis
- Muscle: in animals it has muscle-sparing and growth effects; human evidence for this is weak
The fat loss effect is real but modest compared with a calorie deficit, and the body quickly adapts: beta receptors downregulate within a few weeks, so the effect fades while side effects can persist.
Clinical reference doses
Where clenbuterol is approved for asthma, the usual adult dose is about 20 micrograms twice a day. Doses used for cutting are often several times higher.
Side effects
- Heart: rapid heart rate, palpitations, raised blood pressure; at high doses, irregular rhythms and heart muscle injury have been reported
- Low potassium, which adds to heart rhythm risk and causes cramps
- Tremors, anxiety and insomnia
- Muscle cramps, often severe
- Headaches and sweating
Clenbuterol overdoses are a recurring cause of poison centre calls. Chest pain, a heart rate that stays very high at rest, fainting or severe palpitations need emergency care.
Reducing risk
- Check resting heart rate and blood pressure daily
- Get enough potassium and stay hydrated; see our electrolytes guide
- Avoid combining with other stimulants, high caffeine or T3
- Don’t use it with heart conditions, high blood pressure, anxiety disorders or an overactive thyroid
Legal status in Canada
Clenbuterol isn’t an anabolic steroid and isn’t listed in the Controlled Drugs and Substances Act. It isn’t approved for human use in Canada. It’s prohibited in sport at all times.
Buying clenbuterol in Canada
We stock Zionova Clenbuterol (50 mcg tablets) and Clen 75 Genetix Pharma (75 mcg tablets), both in bottles of 50. Check strength carefully: the difference matters with a drug this potent. See the weight loss page, and our guide to semaglutide, which has far stronger weight-loss evidence.
Frequently asked questions
Is clenbuterol a steroid?
No. It’s a beta-2 agonist bronchodilator, not an anabolic steroid.
Does clenbuterol burn fat?
Modestly, by raising metabolism and fat breakdown. The effect fades within weeks as receptors adapt.
Is clenbuterol bad for your heart?
It raises heart rate and blood pressure and can lower potassium; high doses have been linked to heart rhythm problems and heart muscle injury.
Is clenbuterol legal in Canada?
It isn’t approved for human use and isn’t listed in the CDSA.
Products mentioned in this guide
This article is general information for adults in Canada, not medical advice. Talk to a doctor or pharmacist before using any prescription drug, anabolic steroid or research compound, and get bloodwork done. If you’re in crisis, call or text 9-8-8 (Suicide Crisis Helpline) any time.
