In case your main goal is burning fat, Clenbuterol is an obvious choice. However, you can get even more effects from it, and get an even leaner physique as a result, if you run it in a stack. Here’s how it works.

Clenbuterol Mechanism of Action

Clenbuterol is a non-steroidal beta-2 agonist. You’ve heard it a thousand times, but what does it actually mean? In simple terms: 

Agonist is just a fancy way to say “activator”. Clen’s only function in the body (if we’re talking about fat loss) is to activate the beta-2 receptors.

Beta-2 receptors are located all around your body, on top of cells in all sorts of tissues. When Clenbuterol “activates” these receptors, it triggers a series of chemical reactions inside the cell. These reactions increase the activity of an enzyme called “adenylate cyclase”, which in turn increases the production of a molecule called cyclic AMP (cAMP). 

cAMP is what you really need: this molecule plays a crucial role in all metabolic processes in your body, such as regulating the breakdown of stored fat and the production of heat. The more cAMP you have — the faster your body destroys fat tissue.

Of course, it’s not all that simple, but now you know the general concept of what exactly “beta-2 agonist” stands for and how these fat burners work.

The problem with Clenbuterol Tolerance

Why don’t we all take Clenbuterol all the time and never get fat? The problem is, tolerance is a thing. 

Your beta-2 receptors get “tired” easily from Clen. When you keep them “activated” all the time, they get desensitized, and just stop reacting to Clen at all. 

Your body can “react” to the same dose of Clenbuterol for just 2 weeks straight. Afterwards, it just stops working. And sure, 2 weeks is not enough to get the fat burning effect you expect from Clen in the first place. 

There are 3 ways to “trick” tolerance: raise the dose, take pauses, and take Ketotifene. 

Should you raise the dose of Clen?

One possible solution is to increase the Clenbuterol dosage gradually. That’s what many athletes do: 

  • Start with 20mcg ED;
  • Get to 40mcg ED in 2-3 days;
  • 60 by the end of the first week;
  • And so on. 

Is it something we recommend? No way. Those who can do it are either genetically “lucky” to have no adverse effects from Clenbuterol or just run bunk (aka empty and underdosed) Clen and start getting the effects in high doses only. 

Keep in mind that Clenbuterol is one powerful compound, with all the elevated cAMP in your blood you can expect it to give you a ton of side effects: 

  • Nausea;
  • Drowsiness;
  • Headaches and hot flashes;
  • Disturbed sleep;
  • Cramps and tremors;
  • Sometimes — chest pain, vomiting, and extreme sweating. 

All these side effects are dose-dependent. You get a rather low risk of experiencing them at a mild dose, but the more you take — the more dangerous it gets.

Just take pauses?

It’s an obvious, and a classic approach. If your beta-2 receptors can “react” to Clenbuterol for just 2 weeks straight — fine! get the best out of those 2 weeks and let them “rest” for some time, so they get the ability to react to Clen again. 

2 weeks on — 2 weeks off is one of the most common ways for athletes to take Clenbuterol. 

For 2 weeks, you run a mild dose of Clenbuterol. For weeks 3 and 4 you ride with no Clen, just cardio, drinking a lot of water, eating right, and so on. For weeks 5 and 6 you get Clen back. Your receptors are ready for it and you get another round of an increased metabolic rate. 

Is it convenient, though? You’re pretty much wasting your time, lose fat slower than you could, and get less results in the end.

How Ketotifen Helps

Ketotifen is an antihistamine compound. In its original intended use, it’s supposed to help people with allergies. However, it does not one, but three things in the process:

  1. Blocks histamine (the substance that is released by the body in response to an allergen, the exact thing that causes those with pollen allergy start itching, crying, and swelling);
  2. Reduces the activity of certain immune cells;
  3. And increases the sensitivity of beta-2 receptors.

The third part looks exactly like what you need with Clenbuterol, and that’s right: Ketotifene makes your beta-2 receptors more sensitive, so they need less Clenbuterol to trigger the production of cAMP and boost your weight loss.

It’s like increasing the dose in terms of results, but instead — you make the same dose more effective. 

Clenbuterol and Ketotifen Stack Results

To sum it up, without Ketotifen, your only options to get the effects after 2 weeks are:

  • Increase the dose — but get more negative side effects and put more pressure on your body;
  • Take breaks — but get less notable results and waste your time, taking Clen just for 2 weeks at a time.

With Ketotifen, you:

  • Can effectively use Clenbuterol for 6 to 8 weeks straight, without raising the dosage;
  • Get better results without wasting your time on breaks;
  • Get more benefits with less dose-dependent side effects.

if it sounds like a win-win — you’re absolutely right. 

Consider the extra benefits as well:

  • Both Ketotifen and Clenbuterol are Health Canada and FDA-approved;
  • Ketotifen is not the most expensive thing on the market, you can get 100 tabs of 1mg for around 70-100$, which is enough for 2 full 8-week-long cycles;
  • Ketotifen reduces Clenbuterol’s side effects, including tremor, headaches, and nausea;
  • And finally, Ketotifen normalizes the heart rate that Ketotifen speeds up, so you get less cardiovascular risks. 

Clen without ketotifen is one powerful, tried-and-true weight loss booster. However, WITH Ketotifen, Clen also gets significantly more effective and safer at the same time.

Other Stack Options


Yohimbine, made by processing the bark of the yohimbe tree. It works by blocking a type of receptor in your body called alpha-2 receptors, which are found in fat cells.

When alpha-2 receptors are blocked by Yohimbine, it can lead to an increase in the activity of an enzyme called hormone-sensitive lipase (HSL). HSL is responsible for breaking down stored fat — the one on your belly, thighs, and so on. 

Beta-2 agonist Clenbuterol and Alpha-2 antagonist Yohimbine do the same thing: boost the breakdown of fat tissue. However, they do it from two opposite “flanks”, without intervening in each other’s mechanism of action. That’s why Yohimbine is a perfect stack for Clenbuterol.


This is your final stack option. T3 aka Cytomel is a thyroid hormone that binds to specific receptors called thyroid hormone receptors (TRs) all throughout the body, including the liver, muscles, and fat tissue.

When T3 binds to these receptors, it triggers a series of chemical reactions inside the cell that ultimately lead to an increase in the rate at which your body burns calories and utilizes energy. 

T3 has a complex mechanism of action, so we’ll cut it down to just the basics: the increased calorie burning rate leads to faster fat breakdown (though muscle tissue also gets “burned”, that’s why you want to be careful with T3). It does not react with Clen or Yohimbine, and you can take all three together to get 3x effectiveness in weight loss. 


Clenbuterol, Yohimbine and T3 are a popular stack, it has been around for decades, so there are plenty of pre-made mixes of it on the market. One of the options, YCZ by Apoxar, contains 25 mcg of Clenbuterol, 12.5 mcg of T3, and 2.5mg of Yohimbine in one tablet. You can take them separately or can take one YCZ pill and get the same effects, the only difference is convenience (one pill instead of three).