How Long Does It Take for Semaglutide to Work? What Happens Week by Week

You start semaglutide and step on the scale a week later. The number has barely moved. That is normal, and the trial data explain why.

The answer depends on what “working” means to you. Hunger can change within weeks. Weight changes over months. The main trials measured their result at 68 weeks, well over a year in.

The first four weeks

Every Wegovy course starts at 0.25 mg a week ^[1]. That dose is there to build tolerance. It is not a maintenance dose, and it is about a tenth of the 2.4 mg target.

Semaglutide also takes time to build up. Its half-life is about a week ^[1]. The Ozempic label says steady levels are reached after 4 to 5 weeks of weekly doses ^[2].

So each new dose step needs about a month to settle. The full ladder is set out in semaglutide dosage.

When appetite changes

Appetite is where the drug shows first. One trial gave 72 adults with obesity semaglutide, raised to 2.4 mg, or placebo for 20 weeks ^[3].

At week 20, the semaglutide group ate 35% less at an all-you-want lunch. They reported less hunger, more fullness and fewer cravings. Their body weight was down 9.9%, against 0.4% on placebo.

A later 60-week trial of 120 adults asked whether that lasts ^[4]. People on semaglutide ate about 292 fewer calories at the test lunch at week 20, and about 270 fewer at week 60.

The feeling of less hunger faded, though. By weeks 40 and 60, appetite ratings no longer differed from placebo. The authors concluded that eating fewer calories drives both the loss and its upkeep, even as some felt effects fade.

Month by month

Here is the path the trials describe for the weekly injection. These are group averages. Your own pace can be faster or slower.

When the full effect arrives

STEP 1 followed 1,961 adults without diabetes for 68 weeks ^[5]. Weight fell 14.9% on semaglutide and 2.4% on placebo.

By week 68, 86.4% of the semaglutide group had lost at least 5%. Some 69.1% had lost at least 10%, and 50.5% at least 15%.

The label’s run-in trial shows the same shape from another angle ^[1]. Everyone took semaglutide for 20 weeks first. Mean weight in the group that went on to be randomized fell from 107.2 kg to about 96 kg in that time.

Those who reached 2.4 mg were then randomized. People who kept taking it lost a further 7.9% by week 68. People switched to placebo regained 6.9%.

So weight kept falling well after week 20 for those who stayed on it. The trial evidence on stopping is covered in what happens when you stop taking semaglutide.

Fast responders and slow ones

Not everyone moves at the average pace. A head-to-head trial of semaglutide and tirzepatide looked at who lost 15% or more by week 24 ^[6].

On semaglutide, 21% did. On tirzepatide, 44% did. The fast responders were more likely to reach every weight-loss threshold by week 72.

They also had more stomach, bowel and gallbladder side effects. They finished the trial at similar rates to everyone else. For the tirzepatide side of that trial, see how much weight you can lose on tirzepatide.

What to watch for in your first months

Track your appetite as well as the scale. A change in how much you want to eat is the earliest signal the trials measured.

Give each dose step its 4 weeks before judging it. If you have been on the maintenance dose for a few months with little change, that is the conversation to have with your prescriber.

To compare online prescribers who manage semaglutide, see the weight-loss peptide rankings.