How Semaglutide Acts on the GLP-1 Receptor
GLP-1 (glucagon-like peptide-1) is a hormone released naturally by the gut after eating. It acts on the GLP-1 receptor, signalling to the brain that you are full, slowing the rate at which food leaves the stomach, and supporting blood sugar regulation. Semaglutide is designed to bind to and activate that same receptor, producing similar effects for a sustained period after each weekly injection.
What this means in practice
Because semaglutide activates the GLP-1 agonist pathway, many people report a noticeable reduction in appetite and a quietening of what is sometimes called "food noise" — the persistent background urge to eat. Gastric emptying also tends to slow, which contributes to a prolonged sense of fullness after meals. These effects are commonly reported, though they vary considerably from person to person.
How it differs from tirzepatide
Tirzepatide (Mounjaro) acts on both the GLP-1 receptor and a second receptor called GIP, making it a dual agonist. Semaglutide targets the GLP-1 receptor alone. Both are prescription-only medicines; which is appropriate for any individual is a decision made by their prescriber, not something to determine from a comparison article. You can read more in our overview of Mounjaro (tirzepatide) for a factual summary of how the two medicines differ mechanically.
Commonly reported side effects
Because semaglutide slows gastric emptying and acts on appetite centres, gastrointestinal effects — nausea, constipation, diarrhoea, indigestion — are among the most commonly reported, particularly in the early weeks or after a dose adjustment. Fatigue and headache are also frequently noted. These are generally described as most noticeable early in treatment and often ease over time, though this is not universal. According to NHS guidance, side effects should be discussed with your prescriber or doctor, especially if they are persistent or severe.
average weekly weight change in the first 16 weeks of Mounjaro & Wegovy use*
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One of the most practical things you can do while taking a weekly injectable medicine is keep a consistent record of how you feel — and GLP Trackr's side-effect tracker is built precisely for this. Log symptoms like nausea, fatigue, or digestive changes after each dose, and the app surfaces patterns over time so you can see whether effects are linked to timing, food choices, or dose stage. That kind of structured log is genuinely useful to bring to a prescriber appointment.
Alongside side-effect tracking, the daily check-in lets you record mood, energy, sleep, and appetite in under a minute each morning — building a picture of how your body is responding week by week that goes well beyond the scale. Weight and measurement charts show your transformation across the full arc of your journey, not just this week's number.
If you notice symptoms that are severe, persistent, or worry you at any point, contact your healthcare professional promptly — GLP Trackr helps you record what is happening, but it is not a substitute for clinical advice. Any concerns about your dose or how the medicine is affecting you belong with your prescriber or doctor, who knows your full history. You can also report unexpected side effects to your national reporting scheme (such as the UK's Yellow Card scheme) as directed by your healthcare professional.
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Start every day with a 60-second wellness check-in. Log how you're feeling, track nausea, appetite, energy, and mood — giving you and your care team a complete picture of how your medication is working.
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Log every dose with a single tap. Track your dose history, phase in your cycle, estimated medication levels, and upcoming injection dates — with reminders so you never miss a scheduled shot.
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Frequently asked questions.
It means semaglutide binds to and activates the GLP-1 receptor, mimicking the natural gut hormone GLP-1. This is associated with reduced appetite, a sense of fullness, and slower gastric emptying — effects that are commonly reported by people taking Wegovy.
Semaglutide activates only the GLP-1 receptor, while tirzepatide (Mounjaro) activates both the GLP-1 and GIP receptors. Both are prescription-only medicines. Which is suitable for an individual is a decision for their prescriber or doctor, not something to determine from a comparison alone.
Nausea, constipation, diarrhoea, indigestion, fatigue, and headache are among the most commonly reported effects. They are often most noticeable early in treatment or after a dose change and tend to ease over time, though this varies. Always discuss persistent or severe symptoms with your healthcare professional.
Yes. GLP Trackr's side-effect tracker lets you log symptoms after each dose and spot patterns over time. The daily check-in records mood, energy, and appetite each morning. Together these create a detailed record you can share with your prescriber — though the app does not replace their advice.