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Living with it

Your first month on a GLP-1

The first month is the least representative stretch of the whole treatment. The medicine is building up, the dose is at its lowest, and your body is meeting it for the first time. It is also the month that sets up everything after it — which is a good reason to start the record on day one.

By the Cafeity teamUpdated 3 min read

The short answer

In the first month on a GLP-1, the medicine is still building up — weekly semaglutide takes 4 to 5 weeks to reach a steady level and tirzepatide about 4 weeks — and treatment starts at a low dose that is increased later.12 Appetite often changes within days. Gastrointestinal side effects such as nausea are common in the early weeks and around dose increases, and usually ease.32 It is a good month to set up the basics: your first injection shown by a clinician, a site-rotation habit, regular meals with protein, fluids, and a starting weight.

Week one

  • The first injection. The patient information expects a healthcare provider to show you how to inject before your first dose.2 Ask for this if it has not been offered.
  • Levels peak quickly. Semaglutide peaks 1 to 3 days after an injection; tirzepatide at a median of about 24 hours.32 Some people notice appetite change within days.
  • Side effects may start. Nausea, fullness and changes in bowel habit are the commonest. See when side effects start and how long they last.

Weeks two to four

The medicine is still accumulating: each weekly dose arrives while about half of the previous one is still there, so the level rises for four to five weeks before settling.1 That is one reason the first month is not a fair preview of later months — for better or worse. It is also why the scale in week two says little; see why weight is best read as a trend.

What to set up in month one

  • A starting weight, taken the way you will take every future one — same time, same conditions.
  • A site-rotation habit — the printable chart numbers the zones.
  • Regular meal times with protein first, because hunger may stop reminding you. See eating with no appetite.
  • Fluids through the day.
  • Storage sorted — most pens live in the fridge; see storage and travel.
  • Your questions for the first follow-up, written down — see questions to ask your doctor.

After the first month

Most weight-management labels increase the dose in steps over several months, and the labels describe gastrointestinal side effects as most common during those increases.32 The pace is set by your prescriber — not by how you feel, and not by an app. A record of how each step went is what helps them decide.

When to contact your prescriber

Keeping a record of it

Cafeity is built to start on day one: log the first dose and site, a starting weight, and meals and symptoms as they come. The estimated curve shows the first weeks building up, so week one is not mistaken for the norm.

Cafeity dose screen: an estimated medication-level curve labelled "Estimate based on published half-life. Not a measurement", the last dose, the injection site (stomach, lower left), a countdown to the next scheduled dose and a side-effect check-in.
The first dose, with its site.
Cafeity Today screen: day 1 of 7 since the last dose with the estimated level at 97% of peak, fibre 21 of 25 g, protein 110 of 100 g, steps, water 850 ml of 2.4 L, the next logged dose and the weight trend.
Protein, fibre and water from day one.

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Common questions

What happens in the first week on a GLP-1?
Levels peak within days of the first dose, and many people notice appetite change and some nausea or fullness. The dose is at its lowest, and the medicine is still building up.32
Why have I not lost much weight in the first month?
The first month is at a starting dose and the medicine is still accumulating; in the trials weight loss continued over many months.4 Judge progress on a trend, not the first weeks.

Sources

  1. Semaglutide injection for type 2 diabetes — US prescribing information DailyMed, US National Library of Medicine, version published 10 June 2026
  2. Tirzepatide injection for weight management and obstructive sleep apnoea — US prescribing information DailyMed, US National Library of Medicine, version published 2 September 2026
  3. Semaglutide injection and tablets for weight management — US prescribing information DailyMed, US National Library of Medicine, version published 30 June 2026
  4. Once-weekly semaglutide in adults with overweight or obesity (STEP 1) Wilding JPH et al. New England Journal of Medicine 2021;384:989–1002

Written by the Cafeity team from the sources listed here. Figures from prescribing information are quoted as the label states them; trial results are averages from those trials, not predictions for any one person. This page has not yet been reviewed by a clinician — see the editorial policy for how pages are researched and corrected.