Wegovy Month 4: what the evidence says about weeks 13 to 16

Where the STEP 1 evidence puts weight loss at this point

The STEP 1 trial, published in the New England Journal of Medicine, followed 1,961 adults with obesity over 68 weeks on semaglutide 2.4 mg alongside lifestyle support. Weight loss did not arrive all at once: the curve was steepest in the first six months and continued past them. At week 16, participants on the active treatment had typically lost roughly 8–10% of their starting weight, depending on starting BMI and how well the titration had been tolerated. The 15% average figure that gets quoted most often reflects the full 68-week picture at maintenance dose, not a month-four result.

That distinction matters, because one of the most common misconceptions people carry into month four is that if they are not yet down 10–15%, something has gone wrong. The data tell a different story: the largest single jumps in loss often appear after the 2.4 mg dose is established, which for most people on the standard schedule happens around week 17. If you want a closer look at what one month of Wegovy typically involves in terms of dosing and early expectations, that context can help explain why month four feels so different from the start. Month four is the run-up, and it counts.

If you are thinking about where you are on the treatment ladder, our Wegovy overview page covers the full licensed titration pathway in plain language.

What tends to change in your body and appetite during weeks 13–16

By month four, the pharmacology is doing most of what it is going to do at the current dose. Gastric emptying is slower, meaning food stays in the stomach longer and the feeling of fullness arrives sooner and lingers. GLP-1 receptor activity in the brain is also affecting how rewarding food feels, many people report that foods they found hard to resist simply become less interesting, not through willpower but through biology.

Practically, this often shows up as smaller portions feeling sufficient, a lower drive to snack between meals, and occasional days where appetite is genuinely low. The NHS semaglutide medicines page notes that gastrointestinal side effects (nausea, loose stools, constipation, indigestion) are most common at the start of treatment or after a dose increase. If you have moved to 1.7 mg around weeks 13–14, a short return of those symptoms is normal and usually settles within two weeks.

Protein intake and hydration deserve attention here. When appetite is suppressed, it is easy to eat less of everything, including protein. Maintaining adequate protein helps preserve muscle alongside fat loss, worth raising with your prescriber or a dietitian if you have not already.

Month four compared to earlier months on Wegovy

People arriving at month four will have been through a lot of adjustment already. If you started at the beginning, you will recognise how different this feels from the first month on Wegovy, when the 0.25 mg starter dose was still settling and side effects were front of mind. By month three, most people had reached 1.0 mg and were seeing steady results. Month four consolidates that and moves the dose further.

The graph of progress is rarely a straight line. Some weeks show faster movement on the scale; others feel static. A short plateau at this stage is not evidence that the medicine has stopped working. Body composition shifts, fluid balance, and the timing of the dose step all influence what the scale says week to week. Tracking a four-week average is more informative than daily readings.

People who transferred to Wegovy from another treatment, or who are comparing notes with friends who started at different times, can find month four a useful point to recalibrate expectations against the actual trial evidence rather than anecdotal comparisons. Our month two page covers what the earlier phase typically looks like for context. For a detailed picture of the physical and appetite changes that tend to emerge once the first month is complete, our page on Wegovy after 1 month sets out what most people notice as the titration progresses.

Ongoing safety and when to contact your prescriber

Month four is well within the period where your prescriber should be reviewing your progress before any repeat supply. That review is not just administrative: it is the point at which dose appropriateness, tolerability and any emerging concerns are properly assessed. At nume, a GPhC-registered Independent Prescriber reads every repeat request (a real clinician, not an automated filter) before treatment continues.

Some symptoms warrant prompt medical attention rather than waiting for a scheduled review. Severe stomach pain that radiates to the back, with or without vomiting, should be assessed urgently, as the MHRA highlighted acute pancreatitis as a known, if uncommon, risk in its January 2026 Drug Safety Update for GLP-1 medicines. Gallbladder pain, signs of an allergic reaction, or persistent vomiting causing dehydration also need prompt review. If you are unsure whether a symptom is significant, contact your prescriber's aftercare team. At nume, that support runs seven days a week.

You can also report any suspected side effect directly through the MHRA Yellow Card scheme, patients can submit reports themselves, and that data contributes to ongoing safety monitoring for newer medicines.

If you are not yet on Wegovy and are weighing whether it is the right treatment, our free consultation is the place to start. A prescriber will look at your health history, current medications and what your goals are before making any recommendation.