Guide5 min readFacts checked 26 September 2026
Does your GLP-1 shot wear off by day 5?
It fades, but it does not run out. A weekly GLP-1 shot peaks in your blood about 1 to 3 days after you take it. Then it slowly fades until the next shot. With a half-life of about 5 to 7 days, the level late in the week is lower than at the peak. Some people feel that as hunger or food noise coming back around day 5 or 6. Your own log can show whether that is your pattern.
Claritide draws your estimated levels from the shots you log.
What does half-life mean for a weekly shot?
Half-life is the time it takes your body to clear half of a medicine from your blood. The labels give these numbers:
- Tirzepatide: about 5 days, or 5 to 6 days in people with overweight or obesity.
- Semaglutide: about 1 week.
Retatrutide, which is still investigational, has a published half-life of about 6 days from its phase 2 study.
Half-life describes the medicine in your blood. It does not say how long the effect lasts. The labels also do not say how the level lines up with appetite, day by day. Compounded versions have no FDA label of their own. The figures above come from the approved medicines' labels and, for investigational retatrutide, from its study.
Why do levels build over the first few weeks?
Each weekly shot adds to what is left of the last one. So for the first few weeks, each week's level starts a little higher than the week before. Then it settles into the same weekly rise and fall.
The tirzepatide labels say this steady pattern arrives after about 4 weeks. The semaglutide label for diabetes says 4 to 5 weeks.
What can a levels chart show, and what can it not?
A levels chart, like the one in Claritide, is an estimate. It takes the published half-life, the time to peak from the label and the shots you logged. Then it draws how the level likely rises and falls, as a share of its own recent peak.
It can show when in the week your level is highest and lowest. It can also show how a late or missed shot changes the curve.
It cannot measure your blood. It does not know your body or how you feel. It cannot tell you that a lower level is why you are hungry. It is a map of the week, not a verdict.
Tirzepatide
Half-life about 5 to 6 days
Semaglutide
Half-life about 7 days
| Day since the shot | Tirzepatide | Semaglutide |
|---|---|---|
| Shot day | 48% | 62% |
| Day 1 | 100% | 98% |
| Day 2 | 90% | 99% |
| Day 3 | 79% | 92% |
| Day 4 | 70% | 84% |
| Day 5 | 61% | 76% |
| Day 6 | 54% | 69% |
| Day 7 | 48% | 62% |
Why do people talk about twice-weekly shots?
Because the late-week dip shows up on a chart, and some people feel it. In GLP-1 groups online, people describe splitting a weekly dose into two smaller shots. Others describe a shot every 5 days. The aim they give is a more even week.
The labels for these medicines describe one shot a week. Any other schedule is a change to your prescription, so it is a decision for your prescriber, made with you. If your prescriber does set a different schedule, Claritide can remind you on it. That includes twice a week or every few days.
How do I log hunger by day since my shot?
A daily rating for three or four weeks gives you something real to look at.
- 1.Once a day, at about the same time, rate your hunger from 1 to 10. If food noise is what you notice, rate that.
- 2.Write down the day since your shot. Shot day is day 0.
- 3.Add a few words about anything unusual: a late shot, poor sleep, a party, a new dose.
- 4.At the end of each week, set the days side by side.
If days 5 and 6 come out higher week after week, that is a pattern. One rough week is not. In Claritide, appetite is one of the 1 to 10 scales you can log. It sits in the same record as your shots.
What do I bring to my prescriber?
Bring the pattern, not just the feeling:
- your daily ratings, by day since the shot
- your shot days and times
- any shots that were late or missed
- your questions
A clear week-by-week picture is easier to talk through than a memory of the worst days. Claritide's one-page report puts your shots, side effects and weight on one page. You can print it or save it as a PDF.
Questions people ask
How long does tirzepatide stay in your system?
The labels give tirzepatide a half-life of about 5 days, or 5 to 6 days in people with overweight or obesity. They do not say how many weeks it stays in the blood after the last dose.
How long does semaglutide stay in your system?
The semaglutide label for diabetes says it is still in the blood about 5 weeks after the last dose. The weight-reduction label says about 5 to 7 weeks after the last full dose. Both give a half-life of about 1 week.
Can a GLP-1 be taken twice a week?
The labels describe one shot a week. A twice-weekly schedule is a change to the prescription, so it is your prescriber’s decision. If they set one, Claritide can remind you on it.
Is a levels chart the same as a blood test?
No. A levels chart is an estimate from the published half-life and the shots you logged. It shows how the level likely rises and falls through the week, not how much is in your blood.
Sources
Every fact above comes from one of these, checked on 26 September 2026.
- Zepbound® (tirzepatide) for weight reduction and sleep apnea: US prescribing information, medication guide and instructions for use (Eli Lilly, revised August 2026), DailyMeddailymed.nlm.nih.gov · read 26 September 2026
- Mounjaro® (tirzepatide) for type 2 diabetes: US prescribing information (Eli Lilly, DailyMed version of August 2026)dailymed.nlm.nih.gov · read 26 September 2026
- Wegovy® (semaglutide) injection and tablets for weight reduction: US prescribing information and medication guide (Novo Nordisk, revised June 2026), DailyMeddailymed.nlm.nih.gov · read 26 September 2026
- Ozempic® (semaglutide) for type 2 diabetes: US prescribing information (Novo Nordisk, DailyMed version of June 2026)dailymed.nlm.nih.gov · read 26 September 2026
- Claritide library: retatrutide (investigational), half-life from the phase 2 study in the New England Journal of Medicine, 2023claritide.app · read 26 September 2026
- Claritide lesson: A missed doseclaritide.app · read 26 September 2026
- What people describe: "By day 5, food noise returned strongly", r/TirzepatideRX, 4 September 2026reddit.com · read 26 September 2026
Your shots, your estimated levels and your daily check-in, in one record: Claritide for iPhone.