Clenbuterol is a long-acting beta-2 adrenergic agonist, a small molecule rather than a peptide, sold as 20 microgram tablets for asthma.
Amounts reported for Clenbuterol are listed under Reported protocols, each with its source and study kind. No amount ladder is inferred from them. This is educational source context, not a protocol or recommendation.
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Human study rows are described per source under Reported protocols; they belong to their trial populations and are not a general amount.
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What published studies and recent community write-ups report about amounts, timing and course length. 4 clinical and 3 community-reported rows, each linked to its source. These are descriptions of what others report, not instructions, and nothing here is medical advice.
| Context | Dose | Frequency | Route | Course | Source |
|---|---|---|---|---|---|
| Clinical4 rows | |||||
| German prescribing information (Spiropent tablets)Adults and children aged 12 and over with asthma or chronic obstructive bronchitis with reversible airway narrowing | 20 mcg (1 tablet) per dose; up to 40 mcg (2 tablets) per dose for the first 2-3 days of severe symptoms; maintenance 10 mcg (half a tablet) per dose; never more than 100 mcg (5 tablets) a day | Twice daily, morning and evening, with meals | Oral tablets of 0.02 mg clenbuterol hydrochloride | Continuous maintenance treatment alongside anti-inflammatory therapyNot applicable | Hikma Pharma GmbH, Germany2023 |
| The label states that more than 5 tablets a day brings no extra benefit and raises the chance of serious side effects, that the tablets are not for acute attacks, and that the terminal plasma half-life is about 34 hours. Patients sensitive to beta-2 agonists are advised to start lower. Clenbuterol tablets have no marketing authorisation for people in the United States. | |||||
| FDA-approved veterinary label (Ventipulmin syrup)Horses with airway obstruction such as recurrent airway disease; for oral use in horses only | 0.8 mcg/kg to start (0.5 mL of a 72.5 mcg/mL syrup per 100 lb), stepping up every 3 days to 1.6, 2.4 and then 3.2 mcg/kg if there is no improvement | Twice daily | Oral syrup | 30 days at the effective doseWithdraw after 30 days to see whether signs return; the 30-day course and step-up schedule may be repeated | DailyMed, National Library of Medicine2026 |
| This is the only FDA-approved clenbuterol product in the United States and it is for horses, with a warning against use in food animals. The per-kilogram figures are equine doses from a regulator's animal label and say nothing about safe amounts in people. | |||||
| Poison-centre case series of misuse13 clenbuterol exposures reported to two United States poison control centres, 11 of them for weight loss or bodybuilding | One measured case followed a 4.5 mg ingestion, more than 100 times the 20-40 mcg asthma dose, giving a serum level of 2983 pg/mL | Not stated | Oral grey-market products, some taken with T3 or anabolic steroids | Not stated | Substance Abuse (PubMed)2013 |
| Reported effects were tachycardia, widened pulse pressure, rapid breathing, low potassium, high glucose, ST changes on ECG, raised troponin and creatine kinase, palpitations, chest pain and tremor; effects lasted more than 24 hours and two patients had evidence of myocardial injury. Treatments included activated charcoal, benzodiazepines, beta-blockers, potassium and intravenous fluids. The authors stress that these patients presented as healthy, athletic people rather than typical drug users. | |||||
| Case report and literature review of low-dose toxicityA young adult admitted after an intentional overdose, with a review of published cases in athletes and bodybuilders | Cardiac toxicity reported at doses as low as 20 mcg in one published case, up to deliberate overdoses | Not stated | Oral | Not stated | HCA Healthcare Journal of Medicine (PubMed)2020 |
| The review found that presentations do not track the amount taken, ranging from nausea to myocardial ischaemia, rhabdomyolysis and cardiogenic shock, and that no minimum dose free of adverse effects has been identified. Recommended management is intravenous fluids, potassium replacement, benzodiazepines for agitation and beta-blockers or phenylephrine for haemodynamic support. | |||||
| Community-reported3 rows | |||||
| Bodybuilding cutting-cycle write-up | 20-40 mcg per day to start, increased gradually; described as rarely exceeding 120-140 mcg per day | Once daily, early in the day | Oral | 2 weeks on2 weeks off, or continuous use with ketotifen described as a way to reset beta-2 receptors | Community resource2026 |
| This steroid-community site describes clenbuterol as a cutting-phase addition stacked with anabolic steroids, which is exactly the use pattern in the poison-centre series above. Its upper figures are three to seven times the 20-40 mcg asthma dose and above the 100 mcg daily ceiling on the German label; none of it is supported by a human trial. | |||||
| Consumer health summary | 20-40 mcg per day when prescribed for asthma; athletes described as using varying higher amounts in on-and-off cycles | Not stated | Oral | Not stated | Community resource2025 |
| A medically reviewed consumer article updated in May 2025 records that clenbuterol is banned for human use in the United States, prohibited by WADA at all times, and linked to fast heart rate, atrial fibrillation, myocardial ischaemia and, in poisoning cases, seizures, rhabdomyolysis and cardiogenic shock. It notes that even small amounts can cause toxicity. | |||||
| Vendor liquid listing | 100 mcg/mL in a 30 mL dropper bottle (3,000 mcg total) | Not stated | Liquid research preparation in a 30 mL bottle | Not stated | Community resource2026 |
| This is a vendor claim: the vendor sells clenbuterol as Clen, a 100 mcg/mL liquid for beta-adrenergic pathway research, and states no dosing. One millilitre of this liquid equals five 20 mcg asthma tablets, which is the German label's entire daily ceiling. | |||||
The approved asthma label starts at 20 mcg twice daily, or up to 40 mcg twice daily for the first two or three days of severe symptoms, then drops back once breathing improves. Community cutting write-ups also start at 20-40 mcg a day, but with the intention of climbing.
Community sources describe raising the dose every few days toward 120-140 mcg a day over a two-week block, taken early in the day to limit insomnia. The label ceiling for asthma is 100 mcg a day, and the poison-centre series shows effects persisting beyond 24 hours because of the 34-hour half-life.
Two weeks off is the convention described in community material, justified by beta-2 receptor desensitisation; some write-ups replace the break with ketotifen. No human study has tested either pattern, and the only regulator-defined course, the 30-day equine regimen, ends with withdrawal to see whether signs return.
Plus 3 community resources (dosing guides, forum threads and vendor write-ups), reported above but not linked.
Clenbuterol is a long-acting beta-2 adrenergic agonist, a small molecule rather than a peptide, sold as 20 microgram tablets for asthma and chronic obstructive bronchitis in Germany and other countries outside the United States and, as Ventipulmin syrup, as an FDA-approved treatment for airway obstruction in horses. It is widely misused for fat loss and muscle gain because of the repartitioning effect first seen in livestock, and WADA prohibits it at all times as an anabolic agent with no reporting threshold. Human data outside asthma consist of one small randomised heart-failure study, poison-centre case series and case reports of tachycardia, low potassium and heart muscle injury after grey-market tablets and liquids.
These themes describe recurring questions in published research. They are not claims of effectiveness or recommendations for use.
Energy balance, body composition and incretin signaling.
Androgen receptor modulators, myostatin pathways and exercise-mimetic research.
The label states that more than 5 tablets a day brings no extra benefit and raises the chance of serious side effects, that the tablets are not for acute attacks, and that the terminal plasma half-life is about 34.
This is the only FDA-approved clenbuterol product in the United States and it is for horses, with a warning against use in food animals. The per-kilogram figures are equine doses from a regulator's animal label and say.
Reported effects were tachycardia, widened pulse pressure, rapid breathing, low potassium, high glucose, ST changes on ECG, raised troponin and creatine kinase, palpitations, chest pain and tremor; effects lasted more.
The review found that presentations do not track the amount taken, ranging from nausea to myocardial ischaemia, rhabdomyolysis and cardiogenic shock, and that no minimum dose free of adverse effects has been.
Study models remain visible so laboratory and animal findings are not mistaken for established human outcomes.
4 protocol rows on this page come from human trials, trial registrations, regulator labels or reviews of human data. Approval status and populations are stated per row.
3 rows record what blogs, vendor write-ups or forums describe for Clenbuterol. None has been verified against primary literature.
Sequence, synonyms and registry identifiers as recorded in PubChem, the National Library of Medicine's open chemistry database. Formula, mass and CAS number are summarized at the top of the page.
Clenbuterol, Spiropent, Ventipulmin (veterinary), NAB 365, Contraspasmin, Monores, UNII XTZ6AXU7KN, Clenbuterol hydrochloride (CID 5702273)
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1-(4-amino-3,5-dichlorophenyl)-2-(tert-butylamino)ethanol
7 curated references, each with its journal, year and study model, plus 3 community resources reported but not linked.