Understanding how your GLP-1 medication works throughout the week helps you plan meals and activities more strategically. The key concept is the medication's half-life and how it creates peaks and troughs of effect.
Half-life and peak effect
Every medication has a half-life, which is the time it takes for your body to reduce the active concentration by half. Semaglutide has a half-life of about 7 days, meaning it builds up gradually over 4 to 5 weeks until it reaches a steady state. At steady state, the medication level stays relatively stable throughout the week.
Tirzepatide has a longer half-life, around 5 days. Liraglutide is shorter, approximately 13 hours, which is why it is a daily injection rather than weekly.
At steady state, you experience the full effect of the medication throughout the week. The appetite suppression is not absent on day one and maximal on day seven. Instead, it plateaus at a relatively consistent level.
Planning around your injection day
Some people find that they feel the effects more strongly on days 1 and 2 after injection. Others feel more hungry toward the end of the week. Neither pattern is universal, and both are within normal variation.
If you notice stronger appetite suppression in the first two days, you can plan larger or more protein-rich meals during that window. If you feel more hungry toward the end of the week, having lower-calorie but satiating options available can help.
Consistency matters more than optimization
While understanding your patterns is useful, over-optimizing around injection timing can create unnecessary stress. Taking your injection at the same time and day each week is more important than whether that time is morning or evening.
If you need to change your injection day, it is generally fine to shift by a day or two. Just aim to maintain consistency after the change.
How PeptPro helps
PeptPro has a medication level display that shows where you are in your weekly cycle. See the app here.
If you log your meals and appetite levels consistently, you can review the patterns and see whether your experience matches the theoretical expectations. The data helps you understand your own response rather than relying on general advice.
PeptPro also reminds you to take your injection at the same time each week, which supports the consistency that matters most. Start tracking here.
