The numbers look like trivia. Semaglutide is 100 percent at one receptor. Tirzepatide is somewhere around 5 percent at that same receptor. Retatrutide is about 40 percent. Read on their own they mean nothing. Read correctly, they are the difference between a compound that makes you nauseous for a week and one that barely registers, and between a compound that only quiets your appetite and one that turns up your body heat.

This is not about which compound is strongest. It is about which receptors each one turns, and how far. That distance is what you actually feel. Once the numbers make sense, your side effects make sense too. Everything below is for research and educational purposes only. It is a walk through what the published data shows, not medical advice and not a recommendation to run anything.

A receptor is a control point on the surface of a cell. The simplest way to picture it is a dial. Your hormones turn these dials up and down all day, and that is how your body sends signals. GLP-1 compounds work by copying the hormones your body releases after you eat and turning those same dials. So the whole thing comes down to two questions: which dial does a compound turn, and how far does it turn it.

The percentage is the answer to that second question. It is how far a compound turns one dial, and it is always measured against your own natural hormone turning that dial all the way. Your own hormone is the 100 percent mark. So 100 percent means the compound turns the dial exactly as hard as your body does. Five percent means it barely moves it. Forty percent means it turns it almost halfway. And a compound can even push a dial past 100 percent, which means it turns that dial harder than your body ever does on its own. Hold on to that last one, because it is the key to understanding retatrutide.

One honest caveat before the numbers. These percentages are approximations drawn from potency and activation data in the published research, and different studies measure slightly different things. Some report how tightly a compound grips a receptor. Some report how hard it actually turns the dial once it is attached. Those are not the same measurement, which is why you sometimes see two different numbers for the same compound. Treat the percentages as a reliable map of the terrain, not a precise readout to the decimal.

There are only three dials that matter here, and each one does a different job.

The first is the GLP-1 receptor. It quiets your appetite and slows gastric emptying, which is how fast your stomach empties after a meal. It is also the dial behind most of the nausea. When your stomach is upset on one of these compounds, research points to the GLP-1 receptor as the usual source.

The second is the GIP receptor. GIP is glucose-dependent insulinotropic polypeptide, a gut hormone that helps with insulin and appetite. It helps with blood sugar and appetite without driving that same nausea, and research even suggests that adding GIP activity can take the edge off the nausea that pure GLP-1 activation causes. That makes GIP the quiet helper of the three, and a big reason some of these compounds feel easier to tolerate.

The third is the glucagon receptor, and it is the different one. The first two dials work mostly on your appetite. Glucagon works on your energy instead. It tells your liver to release stored fuel, then pushes your body to burn that fuel as heat, a process called thermogenesis. That is the fat-loss edge researchers associate with retatrutide. But burning fuel that hard takes a toll. Your heart has to work harder to keep up, which is why research links glucagon activity to a higher heart rate, and pushed further it is where disrupted sleep and a wired, jittery feeling tend to come from.

The values above are directional, expressed relative to your own natural hormone at each receptor. They line up with the receptor activation data Eli Lilly has published for these molecules. What matters is the pattern, not the exact figure.

Semaglutide is the simplest of the three, which makes it the right place to anchor everything else. It turns one dial, the GLP-1 receptor, and it turns it up to roughly match your own GLP-1 hormone. That is the full-strength reference point. It does not meaningfully touch the GIP or the glucagon receptor. One dial, turned to full.

Now remember what the GLP-1 dial is. It is the nausea dial. So semaglutide sits right on the nausea dial at full strength, with nothing else in the mix to soften it. Research suggests that is a large part of why it can be the roughest of the three on the stomach. There is no second receptor doing tolerability work in the background. If you want the same head-to-head laid out compound by compound, that is covered in Retatrutide vs Semaglutide.

Tirzepatide is where the nuance starts, and it is the part most people get wrong. If you go looking, you will find two different numbers for tirzepatide at the GLP-1 receptor. Some sources put it around 20 percent. Some put it around 5 percent. People treat that as a contradiction. It is not. Both numbers come from the same research, and they measure two different things.

One number is how tightly tirzepatide grips the GLP-1 receptor, which is called binding affinity. The other is how hard it actually turns the dial once it is attached, which is called functional activation. The part you feel is the turn, not the grip. And on that measure, tirzepatide's GLP-1 activity is weak, sitting well below your own natural hormone and far below where semaglutide sits. That gap between semaglutide at full strength and tirzepatide barely moving the dial is the whole difference in how the two feel on the stomach.

This is deliberate. Tirzepatide is what researchers call an imbalanced or biased agonist, which in plain terms means it is intentionally lopsided. It is gentle on one receptor and strong on the other. The strong one is GIP. Tirzepatide turns the GIP dial up to roughly match your own GIP hormone, dial for dial, and GIP does not drive nausea. Research suggests that pairing, a light touch on the nausea dial and a full turn on the tolerability dial, is a big part of why the stomach tends to handle tirzepatide better than semaglutide even while results stay strong.

That gentler GLP-1 touch is also part of why tirzepatide can be titrated upward more comfortably in research settings, since the receptor driving the nausea is not being pushed hard in the first place. And it is worth saying plainly: tirzepatide does not target the glucagon receptor. Its entire profile lives on two dials, appetite and tolerability, with nothing acting on the energy side. If you have seen the debate framed as a simple case of one compound being stronger than the other, the receptor picture is why that framing misses the point, which is the whole argument in Retatrutide vs Tirzepatide: Why the Debate Is Framed Wrong.

Retatrutide is the one that turns all three dials, and reading it correctly means reading the dials against each other rather than one at a time.

Start with the nausea dial. Retatrutide turns the GLP-1 receptor to roughly partial strength, which the data maps to somewhere around 40 percent of your own hormone. That is meaningfully more than tirzepatide's weak turn. On its own, that single number would predict more nausea than tirzepatide.

But you cannot read it on its own, because of what retatrutide does to the GIP dial. It pushes GIP well past your own hormone. The published potency data suggests it is on the order of nine times as potent as natural GIP at that receptor. That is past 100 percent, harder than your body ever turns that dial by itself. And research suggests that large GIP push helps quiet the nausea the bigger GLP-1 turn would otherwise cause. So the wider GLP-1 setting gets partially offset, and that offset is what shows up in the trial data.

Here is where accuracy matters more than the tidy story. On paper, retatrutide at around 40 percent on the GLP-1 dial against tirzepatide sitting far lower should mean far more nausea from retatrutide. In practice the difference is smaller than the raw numbers predict, but it does not vanish. Retatrutide's nausea still runs higher than tirzepatide's in trial data, and a large part of that is dose-driven. Nausea on these compounds climbs as the dose climbs, and retatrutide was pushed to high doses in its trials. So the GIP dial does not erase the nausea. What it does is keep that wide GLP-1 gap from landing as a huge difference. That balance is a big reason retatrutide can be as effective as it is while remaining usable.

Then it turns the third dial, the one the other two never touch. Retatrutide turns the glucagon receptor to roughly a third of your own glucagon, which fits the data showing it is somewhat less potent than your natural glucagon hormone at that site. Glucagon is where the heat and the heart rate come from. So the trade becomes clear: the nausea may ease thanks to GIP, but a new cost can take its place. Research links glucagon activity to a higher heart rate, and pushed harder to sleep disruption and that wired feeling. More fuel mobilized on one dial, more strain from another. That is the trade retatrutide makes for its power. The role that glucagon dial plays at different doses is worth understanding on its own, which is the subject of Is 4mg of Retatrutide Enough? The Glucagon Receptor Threshold Explained, and the sleep angle specifically is covered in Can't Sleep on Retatrutide?

This is the point that clears up the most confusion. People assume that a higher dose raises the percentage. It does not. The percentage is how hard the dial gets turned at the receptor level, and it has a ceiling that the dose does not move.

Put simply, whether the dose is low or high, retatrutide still turns the GLP-1 dial to roughly the same setting. Raising the dose does not push that setting past its ceiling. What changes is how much force sits behind the same turn. More force means more total effect across your system, and in practice more of the dose-driven side effects like nausea, but the receptor setting itself stays where it is. The percentage tells you the shape of a compound. The dose tells you how hard that shape is being pressed.

Here is what all of this gives you. Once you know the three dials, your side effects start to sort themselves. Feeling sick to your stomach points to the GLP-1 dial. Feeling hot, or your heart racing, points to the glucagon dial. Those are not the same problem. They are two different dials sending two different signals. So instead of guessing what a side effect means, you can start asking which dial you are actually feeling. That question is the one that tells you something real.

One important limit on that framework. It is a way to understand where a feeling is likely coming from, not a diagnosis. Some symptoms that look like receptor effects, an elevated heart rate, ongoing fatigue, a flat mood, can also trace back to markers like thyroid, fasting glucose, or electrolytes that have nothing to do with which dial is turned. That is exactly why a baseline blood panel matters before and during any protocol, so you are looking at data instead of guessing from a feeling.

This is where the dials pay off in real time. Say you move from semaglutide over to tirzepatide. Your nausea often eases, because the GLP-1 dial drops from full strength down to a weak turn. Nothing mysterious happened. You moved off the dial that was driving the feeling.

Then say you move up to retatrutide later on. A little nausea may come back as the GLP-1 dial climbs to partial strength, and a new warm, wired feeling can show up out of nowhere from the glucagon dial that neither of the other two ever touched. That is not the compound failing you, and it is not a sign that something is wrong with you. It is just a new dial getting turned. Once you can name the dial, the feeling stops being a mystery and becomes something you can actually reason about.

Project Theo is an educational research resource. This content is for research and educational purposes only. It is not medical advice, a recommendation, or a protocol, and nothing here should be used to diagnose, treat, or dose anything. Retatrutide is an investigational compound that is not approved for general use. Talk to a qualified medical professional before making any decision about your health.