Your first month on a GLP-1 medicine

What the labels describe for weeks 1 to 4

Every GLP-1 label starts low and climbs, and the stated reason is the same each time: to lower the risk of stomach side effects [1–6]. The first rung differs by product. The table summarises what each US label describes for the opening month. It is a reading of the labels, not a schedule to follow; the dose and pace you use are set by your prescriber.

When the side effects usually show up

The US labels agree on timing more than on numbers. Wegovy® lists its digestive reactions and adds that they were reported most often during dose escalation ^[1]. In the Zepbound® trials most nausea, vomiting and diarrhea happened while the dose was going up and became less frequent later ^[3]. The Foundayo™ label says the same for its tablet trials ^[6].

The European product information for Wegovy® adds durations from the STEP trials. Most digestive events were mild to moderate and short: the median episode lasted 8 days for nausea, 2 days for vomiting and 3 days for diarrhea. Constipation was the exception, with a median of 47 days ^[7]. For liraglutide, the EU product information for Saxenda® says digestive reactions usually appeared in the first weeks and eased within days or weeks of continued treatment ^[8].

Two other effects belong to the early weeks. The tirzepatide and orforglipron labels say the delay in stomach emptying is largest after the first dose and fades with time ^[3][6], which helps explain early fullness. The EU Wegovy® information notes that dizziness, when it occurs, is mainly seen during dose escalation ^[7].

What the large trials measured in the early weeks

The headline results are not one-month results. STEP 1 gave semaglutide or placebo for 68 weeks ^[9], and SURMOUNT-1 gave tirzepatide or placebo for 72 weeks, including a 20-week dose-escalation period ^[10]. Both measured their main outcome at the end.

Some later analyses looked at the opening weeks. A post hoc analysis of SURMOUNT-1 and SURMOUNT-2, funded and partly written by the manufacturer, grouped tirzepatide users by whether their weight had fallen by 5% or more at week 8 ^[11]. In SURMOUNT-1, 1,103 of the 1,775 people analysed had reached that mark. Faster starters had lost a mean 7.9% at week 8 and 23.3% at week 72; slower starters had lost 3.1% at week 8 and still reached 14.6% at week 72 ^[11].

The authors called their findings hypothesis-generating. The analysis left out people without a week-8 weight, could not see who stopped treatment, and was not designed to compare the groups. It also found that stomach side effects were not a useful sign of how well someone would respond ^[11]. Group averages from a trial with regular counselling are not a forecast for an individual.

Why one month says little

Three things make the first month a poor judge. The dose is the lowest one, and for Zepbound® the label is explicit that it is not a treatment dose ^[3]. The trials that defined these medicines measured results more than a year later ^[9][10]. And NIDDK, writing about weight medicines in general, says most of the weight loss happens within the first 6 months, which puts month one at the very start of that window ^[12].

None of this means early weeks are irrelevant. They are when tolerability shows itself, when you learn your own pattern after a dose, and when the record that will inform the next step begins.

What is worth writing down

• Each dose: the date, the time and the injection site, or for tablets the time you took it and when you first ate.
• The first day a symptom appears after a dose and how many days it lasts. Durations are what the EU product information reports, so they are what a clinician can compare ^[7].
• Fluids and bathroom changes. The Wegovy® Medication Guide links fluid loss from vomiting or diarrhea to kidney problems and asks you to drink fluids and to report symptoms that do not settle ^[1].
• Other medicines. The tirzepatide and Foundayo™ labels give specific advice for oral birth control around the start of treatment and each step up, because of the slower stomach emptying ^[3][6]. Ask your prescriber what applies to you.
• Blood sugar, if you have diabetes. The Wegovy® label asks for glucose monitoring before and during treatment, and low blood sugar is more likely with insulin or a sulfonylurea ^[1].
• Weight, if you track it, with the date. One reading means little; a dated series is what you can bring to an appointment.

The end of the month and the first step up

At the end of the opening month, the labels describe the first increase: week 5 for weekly injections and day 31 or later for the tablets [1–6]. The labels also leave room to wait. Wegovy® suggests delaying a step by 4 weeks when a dose is not tolerated, Saxenda® by about a week, and Zepbound® and Foundayo™ describe increases only after at least 4 weeks or 30 days on the current dose ^[1][3][5][6].

Gaps matter too. The Wegovy® label asks for the escalation to start again at a lower dose after 2 or more missed weekly injections, and the Foundayo™ label after 7 or more missed daily tablets ^[1][6]. Whether you move up, stay or step back is your prescriber’s decision, and your notes from this month are the evidence for it.

Ozempic®, Wegovy® and Saxenda® are registered trademarks of Novo Nordisk A/S. Mounjaro® and Zepbound® are registered trademarks and Foundayo™ is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Novo Nordisk or Eli Lilly and Company.