Semaglutide

What it is

Semaglutide is a long-acting copy of glucagon-like peptide-1 (GLP-1), the gut hormone released after a meal. Novo Nordisk modified the human GLP-1 sequence so enzymes cannot break it down quickly, then attached a fatty acid chain that grips albumin in the blood. The result lasts about a week instead of a few minutes.

It is sold under three brands:

• Ozempic, a weekly injection for type 2 diabetes, first approved in the US in 2017.
• Wegovy, a weekly injection at a higher maintenance dose for chronic weight management, approved in the US in 2021.
• Rybelsus, a once-daily tablet for type 2 diabetes.

This is an approved, prescription medicine. It is on this site because it is the reference point every newer GLP-1 compound is measured against.

How it works

Semaglutide activates the GLP-1 receptor. The main effects that matter for weight and blood sugar are:

• Insulin release rises only when glucose is high, and glucagon falls, which lowers blood sugar without much risk of lows on its own.
• The stomach empties more slowly, so a meal lasts longer.
• Appetite drops through GLP-1 receptors in the brain's feeding centres.

Newer drugs add more receptors to the same backbone. Tirzepatide adds GIP, retatrutide adds GIP and glucagon, and CagriSema pairs semaglutide with the amylin analogue cagrilintide.

What the research found

STEP-1: weight loss without diabetes

STEP-1 enrolled 1,961 adults with a BMI of 30 or more, or 27 or more with a weight-related condition, and no diabetes. They were randomised 2:1 to semaglutide 2.4 mg weekly or placebo for 68 weeks, both with a lifestyle programme.

• Mean body weight change was -14.9% on semaglutide vs -2.4% on placebo, a difference of 12.4 percentage points.
• In kilograms, that was -15.3 kg vs -2.6 kg.
• 86.4% of the semaglutide group lost at least 5% of body weight, 69.1% lost at least 10%, and 50.5% lost at least 15%.

SELECT: heart outcomes

SELECT tested the same 2.4 mg weekly dose in 17,604 adults with established cardiovascular disease and overweight or obesity but no diabetes. A first major cardiovascular event (cardiovascular death, heart attack or stroke) occurred in 6.5% on semaglutide vs 8.0% on placebo, a hazard ratio of 0.80.

Dose escalation

The label starts at 0.25 mg weekly and steps up every four weeks to 2.4 mg by week 17. The low starting doses are there for tolerability, not weight loss. The GLP-1 titration tool lays out the published label schedules side by side.

Side effects reported in studies

In the Wegovy label, the most common adverse reactions were nausea (44%), diarrhoea (30%), vomiting (24%), constipation (24%), abdominal pain (20%), headache (14%) and fatigue (11%). In STEP-1 the gastrointestinal effects were mostly mild to moderate and faded over time, but 4.5% of the semaglutide group stopped treatment because of them, against 0.8% on placebo. In SELECT, 16.6% stopped for adverse events vs 8.2% on placebo.

The label carries a boxed warning: semaglutide caused thyroid C-cell tumours in rodents, and it is contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN 2. See the side effect management guide for the wider GLP-1 picture.

Semaglutide vs tirzepatide

These are separate trials with different populations, so the numbers are not a head-to-head result.

Status in the Philippines

Ozempic has been registered with FDA Philippines since 2022, and Wegovy is registered and has been on sale at Watsons since late 2025. Both are prescription medicines: prescribing belongs with a licensed Philippine physician.

Pharmacy prices checked on the pharmacies' own pages on 26 August 2026:

Each weekly pen holds four doses. No verified Philippine price exists for Rybelsus or the Ozempic 2 mg pen. For how these costs compare over a full course, see cost reality in the Philippines.

Enforcement has tightened in 2026. On 14 March 2026 the Philippine College of Physicians issued an advisory against compounded and non-registered Ozempic and Mounjaro, and in May 2026 the NBI and FDA Philippines raided a Pasig clinic.

Local stock Semaglutide 15mg at Primara Labs, delivered in Metro Manila and nationwide. Research use only.

Storage

Unopened pens go in the refrigerator at 2 to 8°C. The Wegovy label allows up to 28 days between 8 and 30°C, which is a real limit in a Manila summer: a pen left in a parked car or through a long brownout can pass 30°C. Keep pens away from the freezer compartment and out of direct sun.