Semaglutide

Semaglutide is a GLP-1 receptor agonist developed by Novo Nordisk. It mimics GLP-1, a gut hormone that increases insulin release, slows stomach emptying, and acts on appetite centers in the brain. One molecule, three brand names:

• Ozempic — weekly injection, approved for type 2 diabetes.
• Wegovy — weekly injection at higher doses (up to 2.4 mg), approved for weight management.
• Rybelsus — daily oral tablet, approved for type 2 diabetes.

What the evidence shows

In the STEP 1 trial (Wilding et al., New England Journal of Medicine, 2021), adults taking weekly 2.4 mg semaglutide lost an average of 14.9% of body weight over 68 weeks, versus 2.4% on placebo. Later trials extended the evidence to cardiovascular risk reduction (SELECT trial, 2023).

What it feels like in practice

The most-reported subjective effects are earlier fullness, reduced appetite, and quieter food noise. The most common side effects are gastrointestinal — nausea affected roughly 44% of STEP 1 participants at some point, mostly during titration.

Semaglutide vs tirzepatide

Tirzepatide is the other major weekly injectable in this space; it targets two hormone receptors instead of one and produced larger average weight loss in its trials. Head-to-head, the SURMOUNT-5 trial (2025) found greater average weight loss with tirzepatide. Averages aren’t individuals, though — response to each molecule varies person to person, which is exactly why tracking your own data matters.