ForumDosing & Titration

Is there any good data on Glucagon levels right after dosing various GLP1s?

20 replies4 peopleDec 11, 2025☆ Follow
Summary

What happens to glucagon levels immediately after the first dose of retatrutide, semaglutide or tirzepatide, and how does glucagon receptor agonism actually drive weight loss?

Retatrutide raises glucagon at the lowest dose but lowers it at higher doses right after the first injection; longer-term data show greater fasting glucagon suppression than GLP-1 agonists alone. Participants conclude that social-media claims of “glucagon goes up to burn fat” are backwards and that the net effect is reduced glucagon signaling. They struggle to find a coherent integrated mechanism and note that most explanations stay at first-order effects without tracing downstream cascades.

What this discussion establishesWhere people disagree

Whether retatrutide ultimately increases or decreases effective glucagon tone; some posts treat the receptor agonist as adding glucagon activity while the trial text claims greater suppression of measured glucagon.

Still open

A clear, step-by-step cascade linking the three agonists to changes in glucagon secretion, insulin, and fat oxidation that everyone in the thread accepts.

Nothing here is advice.

20 replies · 4 people
SlowLedger42archiveopening postDec 11, 2025

Lilly published serum glucagon levels right after the first retatrutide dose. In the chart, glucagon went up at the 0.1 mg dose but dropped at every higher dose tested. I have not found matching first-dose data for semaglutide, tirzepatide or similar drugs. Most published glucagon numbers come after weeks or months of treatment, by which point weight loss has already occurred, so it is hard to tell how much of the drop is from the drug itself versus the weight change.

BlueWillow27archiveDec 11, 2025

Same question. Also looking for a plain-English explanation of how glucagon agonism produces weight loss. I follow the GLP-1 and GIP parts but the glucagon piece is still a black box to me.

SlowLedger42archiveDec 11, 2025
↳ replying to @BlueWillow27

I keep running into the same gap and wonder whether the popular explanations are simply mixing up cause and effect. At the simplest level the agonist should create a false high-glucagon signal somewhere in the gut or brain, which then changes how much glucagon the body itself releases. The open question is whether that signal ultimately raises or lowers endogenous glucagon output. The retatrutide chart shows a clear drop after the shot, which already conflicts with the usual “more glucagon equals more fat burning” line.

BlueWillow27archiveDec 11, 2025

You have exactly described the problem I have been having. Thanks for laying it out clearly. After listening to various online doctors I have started to suspect that even the ones with MDs after their names are not specialized enough in this pathway to give an accurate picture.

SlowLedger42archiveDec 11, 2025
↳ replying to @BlueWillow27

Most commentators know the names of the hormones but have not tried to connect them into a full sequence. That produces statements such as “GLP-1s lower blood sugar by raising insulin,” which is the same description given for sulfonylureas. In reality GLP-1 drugs ultimately reduce insulin needs through weight loss, so the first-order claim is misleading.

SlowLedger42archiveDec 11, 2025

One possible picture, which could easily be wrong: the strong appetite suppression from GLP-1 and GIP agonists creates an energy deficit that raises glucagon in the short term simply because the body has to draw on stores. At the same time the brain receives “I just ate” signals that would normally raise insulin. The two opposing drives coexist until GLP-1 resistance develops and weight loss stalls. Retatrutide’s extra glucagon receptor activity might change that balance in a way the dual agonists do not.

BlueWillow27archiveDec 11, 2025

That sketch feels more consistent with the data than the usual short videos. It would be useful to see any study that actually measures what happens when all three agonists are present together instead of the usual “they combine like Voltron” description.

SlowLedger42archiveDec 11, 2025
↳ replying to @BlueWillow27

The first GLP-1 compounds were developed from the observation that something rises after eating and might fool the brain into thinking a meal has occurred. Later molecules simply added other metabolic hormones in varying ratios, tested them in animals, and moved the best weight-loss candidates forward without a complete mechanistic map. Unlike metformin, where uncertainty was openly acknowledged for years, newer drugs are given simple stories for marketing reasons.

SlowLedger42archiveDec 12, 2025
↳ replying to @BlueWillow27

The paper itself states that retatrutide produces larger reductions in fasting glucagon than GLP-1 receptor agonists alone. The comparison numbers may mix short-term and longer-term measurements, but the authors clearly present greater glucagon lowering as an advantage. That directly contradicts the influencer claim that retatrutide works by raising glucagon.

BlueWillow27archiveDec 12, 2025

If the drug lowers glucagon, then the liver should release less glucose into the blood, which would force greater reliance on fat stores for energy.

SlowLedger42archiveDec 12, 2025
↳ replying to @BlueWillow27

Lower glucagon should in principle reduce both glucose and fat release, yet the body still functions. The real advantage may be greater metabolic flexibility: with lower baseline demands on both insulin and glucagon, the system can adjust more quickly when needed. A study in type-1 diabetic mice showed that lowering glucagon alone allowed the remaining insulin to keep glucose normal.

CopperWillow19archiveDec 17, 2025

I came across a review that covers glucagon and the other hormones tied to these drugs and gives useful background on how the field developed.

SlowLedger42archiveDec 18, 2025
↳ replying to @CopperWillow19

The review is well written and places the current drugs in historical context. One section refers to “adding glucagon back in” and cites retatrutide as the example, yet the trial data show retatrutide lowers measured glucagon more than GLP-1 agonists. The wording may be loose; the agonist can still activate receptors even while actual circulating glucagon falls.

BlueWillow27archiveDec 22, 2025

A recent talk by Dr. Bikman discusses glucagon pharmacokinetics and may be worth watching.

SlowLedger42archiveDec 23, 2025
↳ replying to @BlueWillow27

The talk gives a clear overview. Bikman’s earlier material on the insulin-to-glucagon ratio is also useful background, especially the point that a pure protein meal raises both insulin and glucagon so that blood glucose stays stable.

BlueWillow27archiveDec 23, 2025

Appreciate the consistent level of detail in the posts; they either add new information or show a clearer way to think about the topic without unnecessary attitude.

BlueWillow27archiveDec 23, 2025
↳ replying to @CopperWillow19

Having trouble opening the link that was posted earlier. Could it be shared again?

SharpHarbour71archiveDec 23, 2025

The idea I saw somewhere is that changing glucagon essentially creates a ketosis-like state so more fat is burned to cover the calorie gap.

BlueWillow27archiveDec 23, 2025

That lines up with what Bikman described. Glucagon does not merely copy ketosis; under the right conditions it triggers the reactions that produce ketones even if the body is not technically in ketosis yet.

SlowLedger42archiveDec 24, 2025
↳ replying to @BlueWillow27

True ketosis is simply measurable ketone production, usually tracked by blood BHB. Retatrutide can support reaching that state but does not guarantee it at lower doses, based on personal observation.

CopperWillow19archiveDec 24, 2025
↳ replying to @BlueWillow27

Reposting the resource here for you.

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