How Long Does Wegovy Take to Work? A Week-by-Week Timeline

Short answer: Wegovy acts on appetite from the first dose, but the dose is built up gradually over 16 weeks, so weight loss builds over months: on the usual schedule you reach the 2.4mg maintenance dose from week 17. The UK product information uses 6 months on treatment as the point to judge whether it is working for you. In the STEP 1 trial, average weight loss was 14.9% after 68 weeks, counting everyone who started treatment. Individual results vary.

Two things change on Wegovy, and not at the same pace: your appetite, then your weight. This guide sets out the usual timeline week by week, what the trials found at each point, why some people lose weight more slowly, and when to speak to your pharmacist.

What does it mean for Wegovy to be working?

Wegovy contains semaglutide, which acts on the parts of the brain that control appetite. Its UK patient leaflet says it makes you feel fuller and less hungry, with less craving for food, which helps you eat less and so lose weight. That is why appetite is usually the first thing to change, and your weight follows from eating less.

In an early trial described in the UK product information, people who had taken 2.4mg for 20 weeks took in 35% fewer calories than people on placebo at a meal where they could eat as much as they liked. They also reported more control over eating, feeling fuller, less hunger and fewer food cravings.

For your weight, the product information gives a clear benchmark: losing at least 5% of your starting weight after 6 months on treatment. For someone who starts at 100kg, that is 5kg.

How long does Wegovy take to work?

Wegovy is started low and built up. The UK product information says the dose should be increased over 16 weeks, to make stomach side effects less likely, until you reach the 2.4mg maintenance dose. On the usual schedule that is 4 weeks each at 0.25mg, 0.5mg, 1mg and 1.7mg, then 2.4mg from week 17. For adults with obesity (a BMI of 30 or more) who need additional weight loss, the dose can go up to 7.2mg after at least 4 weeks on 2.4mg, so from week 21 at the earliest. People using Wegovy with a BMI of 27 to 30 stay at up to 2.4mg.

• Maintenance dose reachedWeek 17

  On the usual schedule, 4 weeks at each of 0.25mg, 0.5mg, 1mg and 1.7mg brings you to 2.4mg from week 17.

• First review of results6 months

  The UK product information asks for a decision on continuing if you have lost less than 5% of your starting weight after 6 months on treatment.

The full schedule, and what to do if a step is hard, is in our Wegovy dose schedule.

What happens on Wegovy week by week?

Trial figures are averages from groups of people, not a forecast for any one person. Individual results vary. Your pharmacist reviews you before each increase, and 4 weeks is how long each step usually lasts, not a deadline.

How quickly does Wegovy work in the first weeks?

Weeks 1 to 4. The 0.25mg starting dose is there to get your body used to the medicine, not to be the dose you stay on. Some people notice their appetite change in the first weeks; others notice little until the dose is higher. Neither tells you how you will do later.

Weeks 5 to 16. These are the step-up doses. In the trials, stomach side effects such as nausea, diarrhoea and vomiting were reported most often while the dose was being increased, and most were mild to moderate and short-lived. Constipation tended to last longer. Our guide to Wegovy side effects explains what helps.

Weeks 17 to 20. In the STEP 4 trial (JAMA, 2021), 902 adults took semaglutide for 20 weeks before the main trial began: 16 weeks of dose increases, then 4 weeks at 2.4mg. The 803 who completed those 20 weeks and reached 2.4mg had lost an average of 10.6% of their body weight by then. That figure counts only the people who completed the 20 weeks. Individual results vary.

What can you expect at 6 months and beyond?

Six months is the first fair point to judge Wegovy. On the usual schedule, you will have been on the 2.4mg maintenance dose for about 2 months by then.

The UK product information reports that in STEP 1, after about 6 months (28 weeks), 89.8% of people treated with 2.4mg had lost at least 5% of their weight. Of those who had not, 40.5% went on to reach 5% by week 68. So a slower start does not always mean Wegovy will not work for you. Individual results vary.

What are Wegovy results month by month?

The trials did not report every month, so the figures below come from the points each trial did report, with who each figure counts. They are averages from groups of people, not a forecast for you. Individual results vary.

Does Wegovy work? What the trials found

In the STEP 1 trial (New England Journal of Medicine, 2021), 1,961 adults with a BMI of 30 or more, or 27 or more with a weight-related condition, and without diabetes, took Wegovy 2.4mg or placebo for 68 weeks alongside a reduced-calorie diet and more physical activity. Those on Wegovy lost an average of 14.9% of their body weight, compared with 2.4% on placebo, counting everyone who started treatment. Among people who stayed on treatment, the average was 16.9%. 83.5% lost at least 5% of their weight, compared with 31.1% on placebo. Individual results vary.

In a separate trial of people with type 2 diabetes, average weight loss was lower. In STEP 2 (Lancet, 2021), adults with type 2 diabetes and a BMI of 27 or more lost an average of 9.6% of their body weight over 68 weeks on 2.4mg, compared with 3.4% on placebo, counting everyone who started treatment. Individual results vary.

In the STEP UP trial (Lancet Diabetes and Endocrinology, 2025), adults with obesity and without diabetes lost an average of 18.7% of their body weight over 72 weeks on 7.2mg, compared with 15.6% on 2.4mg and 3.9% on placebo, counting everyone who started treatment. Among those who stayed on treatment, the averages were 20.7% and 17.5%. Individual results vary.

The UK product information also says weight loss in the trials happened whether or not people had nausea, vomiting or diarrhoea. Feeling sick is not a sign that Wegovy is working, and not feeling sick is not a sign that it is not. More on the higher dose is in our guide to Wegovy 7.2mg.

Why am I not losing weight on Wegovy?

If the scale is moving slowly, there is usually a reason, and most are things your pharmacist can help with.

• Your dose is still building. Before week 17 you are still on the step-up doses. Judge Wegovy from around 6 months, not from the first month.

• Missed or late doses. A weekly medicine is taken on the same day each week. If you miss one, our rule is in the box below the list.

• A dose step held back. If side effects mean a step is delayed, or the dose goes back to the previous one, you reach 2.4mg later and the timeline moves with it. The UK product information allows this.

• What you eat and how active you are. The trials gave everyone a reduced-calorie diet (500 kcal a day below their needs) and a target of 150 minutes of activity a week. See what to eat on Wegovy.

• Type 2 diabetes. Average weight loss was lower in the trial of people with type 2 diabetes than in the trial of people without it.

• A pen stored wrongly. A pen that has been frozen, kept too warm or used past its time may not work as it should. See how long Wegovy can be out of the fridge.

• A pen that is not genuine. The MHRA warns of counterfeit pens that closely mimic the licensed ones, and says the only way to be sure of a genuine medicine is a legitimate pharmacy and a prescription. See how to check your medicine is genuine.

• Other medicines and health conditions. Some can make weight loss harder. Tell your pharmacist about everything you take, including anything new.

• A natural slow-down. Weight loss naturally slows over time, and a few weeks with little change can happen while treatment is still working.

For more on plateaus, protein and sleep, see why am I not losing weight on Mounjaro or Wegovy.

Can I stay on a low dose of Wegovy?

The UK product information for the injection names 2.4mg once a week as the maintenance dose for adults, reached by building up over 16 weeks. If stomach side effects are significant, it allows the next step to be delayed, or the dose lowered to the previous one, until they improve. It does not set out a lower dose for adults to stay on for good.

So if a step is hard, tell your pharmacist before your next increase, rather than pushing through or stopping. You decide together whether to wait longer at your current dose. Wegovy tablets are different: their product information says the dose can be kept at the previous level if needed.

What if Wegovy is not working for you?

The UK product information says that if you have not lost at least 5% of your starting weight after 6 months on treatment, a decision is needed on whether to continue, weighing up the benefits and risks for you. NICE's guidance for the NHS (TA875) says the same: consider stopping semaglutide if less than 5% of the initial weight has been lost after 6 months of treatment.

If Wegovy is not working for you, that is a clinical decision to make together, not a personal failure. The review can include how you inject and store your pens, your dose, or a different medicine. If you decide together to stop, our guide to coming off Wegovy explains what happens to appetite and weight afterwards. Coming back after a gap? See restarting Mounjaro or Wegovy after a break.

When should you speak to your pharmacist?

Message your pharmacist:

• Before your next dose increase, if the current step has been hard.
• Before your next dose, if side effects stop you eating or drinking, or vomiting or diarrhoea will not settle.
• Before you restart, if you have missed more than one dose.
• If you are not sure a pen is still usable, or whether you received your full dose.
• If you have been on 2.4mg for some weeks and nothing at all has changed, appetite included.
• At around 6 months, to review your results together.

Urgent symptoms are in the box below. For injecting technique, see how to inject Wegovy.

How does Wegovy's timing compare with Wegovy tablets and Mounjaro?

For Wegovy tablets: Your dose builds gradually: 1.5 mg daily for 4 weeks → 4 mg for 4 weeks → 9 mg for 4 weeks → 25 mg ongoing. Each step lasts at least a month, and you'll only ever have one strength at a time. Never take more than one tablet a day, never combine strengths, and don't repeat a dose if you vomit after taking it.

For Mounjaro, the product information's 5% review comes 6 months after reaching the highest dose you tolerate, rather than 6 months after starting. These are dose schedules, not a measure of results: how much weight people lose, and how quickly, varies from person to person on each of them. See Wegovy pill vs injection and how long Mounjaro takes to work.