Semaglutid

• Drug class: GLP-1 receptor agonist (incretin mimetic)
• Main benefits: Significant weight loss, lower blood sugar, and reduced cardiovascular and kidney risks
• Approval status: Fully approved (FDA/EMA) for type 2 diabetes, obesity (including adolescents aged 12 and up), CVD, and chronic kidney disease
• Available forms: Subcutaneous (Ozempic, Wegovy), oral (Rybelsus, Wegovy tablet)

Semaglutide: How the GLP-1 Agonist Works and What It's Used For

Semaglutide is a prescription medication from the group of GLP-1 receptor agonists. It's widely seen as the gold standard among weight-loss injections. It's a peptide hormone analog, meaning it's a lab-made version of a natural hormone. It mimics the human gut hormone GLP-1 and matches it in 94% of its amino acid sequence. It's used to treat type 2 diabetes, obesity, and to reduce cardiovascular and kidney risks.

Semaglutide comes in two forms: as a subcutaneous injection (Ozempic for diabetes, Wegovy for obesity) and as an oral tablet (Rybelsus for diabetes since 2019, Wegovy tablet for obesity since December 2025). This makes semaglutide the first and so far only GLP-1 drug approved for weight loss both as an injection and as a pill.

How to Use Semaglutide: Injection (Shot) and Tablets

You can take semaglutide in two ways: as a shot under the skin (subcutaneous) or as a tablet (oral). The approved, evidence-based way is only as a finished pharmaceutical product - Ozempic, Wegovy, and Rybelsus are prescription medications.

Subcutaneous (Ozempic, Wegovy): You give the injection once a week under the skin, usually in the abdomen, thigh, or upper arm. Both products come as pre-filled pens with fixed doses - no mixing needed. The dose is increased slowly over about 16 weeks, starting at 0.25 mg per week up to a maximum target dose of 2.4 mg/week (obesity) or 2.0 mg/week (diabetes) [7, 9].

Oral (Rybelsus, Wegovy tablet): You take the tablet once a day on an empty stomach - at least 30 minutes before the first meal, drink, or other medication. Rybelsus (diabetes) is increased from 3 mg/day to 7 mg or 14 mg/day [19]. The Wegovy tablet (obesity) is increased up to 25 mg/day [23]. The oral bioavailability - how much of the drug actually reaches your bloodstream - is much lower than with the injection, which is why the tablet doses are much higher.

Gray market practice: On the gray market, lyophilized semaglutide powder in vials (5-30 mg) is sometimes offered. Users reconstitute it themselves with BAC water and inject it subcutaneously. This practice is unproven and risky: there is no quality control, dosing is error-prone, and sterility is not guaranteed. Semaglutide is regulated as a prescription medication - the gray market route is not compliant with approval.

Semaglutide Dosage: Reconstituting Vials and Calculation Examples

Since semaglutide is sold as a finished pharmaceutical product (pre-filled pen), mixing is usually not necessary. However, vials with lyophilized powder offered on the gray market do require reconstitution. The following example is purely for documentation and is not a recommendation.

Example calculation (unproven user practice): With a vial containing 10 mg of semaglutide powder reconstituted with 2 ml of BAC water, the resulting concentration is 5 mg/ml. For a dose of 0.25 mg (starting dose), you would draw up 0.05 ml (5 units on an insulin syringe U-100). For 1.0 mg, it would be 0.2 ml (20 units). These values are for illustration only and are not dosing instructions.

To correctly calculate doses from vials, you can use the Injection Calculator. General tips on mixing and storing can be found in the Guides.

How Semaglutide Works in the Body

Semaglutide mimics the human gut hormone GLP-1, with a 94% match in its amino acid sequence. It signals the pancreas to release insulin in a glucose-dependent manner while suppressing glucagon. Additionally, it slows stomach emptying, curbs appetite, and reduces so-called 'food noise' - the constant thoughts about eating. By binding to albumin in the blood, it achieves a half-life of 165 to 200 hours, which allows for once-weekly dosing.

Study Results on the Effectiveness of Semaglutide

The effectiveness of semaglutide is backed by one of the largest clinical programs in medical history. The key results:

The STEP Program: Clinical Studies on Weight Loss

The STEP program (Semaglutide Treatment Effect in People with Obesity) includes numerous phase 3 studies with tens of thousands of participants in total. It consistently confirms weight loss of 15 to 20% over 68 weeks at the target dose of 2.4 mg/week subcutaneously. STEP-Teens extended the approval to adolescents aged 12 and up. STEP-HFpEF additionally showed benefits in heart failure with preserved ejection fraction and obesity [25].

Dosage Schedule and Titration of Semaglutide

The study-validated dosing of semaglutide uses slow titration to minimize gastrointestinal side effects.

Titration is done in 4-week steps. If tolerated, you can move to the next level; if not, you can stay on a level longer.

Storage and Proper Handling of Ozempic and Wegovy

Semaglutide pre-filled pens are stored in the refrigerator at 2-8 °C. After first use, they can be kept at room temperature (up to 30 °C) for up to 6 weeks. The tablet must be stored dry at room temperature. Freezing is off-limits for both forms.

More details on proper storage and handling can be found in the Guides. If you want to calculate a dose from a vial, the Dose Calculator can help.

Side Effects and Risks of Using Semaglutide

The most common side effects of semaglutide affect the gastrointestinal tract, with nausea, vomiting, diarrhea, constipation, and bloating occurring very commonly during the dose escalation phase [2]. In clinical studies with Wegovy, 44% of patients reported nausea [2]. A meta-analysis confirms an increased risk of gallstone formation [6]. Rare but serious risks include pancreatitis and gastroparesis. In animal studies, thyroid C-cell tumors were observed; in humans, this link could not be confirmed [2, 7].

A common mistake is increasing the dose too quickly, which leads to severe gastrointestinal discomfort. Another mistake on the gray market is incorrectly reconstituting powder vials with unsuitable solvents or wrong concentrations.

Approval Status and Legal Classification of Semaglutide

Semaglutide is fully approved as a prescription medication. The key approval milestones:

Further studies are underway for MASH (an inflammatory fatty liver disease with liver scarring); approval is still pending. You can find more related drug profiles in the Peptide Library.