Semaglutide

What it is

Semaglutide is a GLP-1 receptor agonist, sold under the brand names Ozempic for type 2 diabetes and Wegovy for chronic weight management. GLP-1 is a hormone the gut naturally releases after eating; semaglutide is a synthetic version engineered to activate the same receptor, but to remain active in the body far longer than the natural hormone does.

In the PeptidesAI encyclopedia, semaglutide is categorized under weight management, the same category as tirzepatide and cagrilintide. It is also available as a compounded, lyophilized (freeze-dried) powder in vials, separate from the branded, pre-filled pens, which some people reconstitute themselves for research or off-label purposes rather than using the FDA-approved injector.

How it's thought to work

Semaglutide selectively activates GLP-1 receptors, which research describes as suppressing appetite, slowing gastric emptying (the rate at which food leaves the stomach), and enhancing the body's own insulin secretion in response to meals. Because it is formulated as a long-acting molecule, it is designed to stay active in the body for an extended stretch of time rather than being broken down quickly the way the natural GLP-1 hormone is, which is part of the proposed basis for its sustained effect on appetite and blood sugar regulation.

What the research says

The STEP clinical trials, a set of trials conducted in humans, demonstrated body weight reduction of up to 16% among study participants over the course of the research. On the strength of this evidence, the FDA has approved semaglutide as Wegovy for chronic weight management and as Ozempic for type 2 diabetes, meaning regulators formally reviewed its safety and effectiveness for those specific uses.

Reported side effects

The most commonly reported side effects are gastrointestinal: nausea, vomiting, diarrhea, constipation, and abdominal pain. Pancreatitis, inflammation of the pancreas, has been reported but appears rare. Separately, rodent studies have found thyroid C-cell tumors associated with semaglutide, though whether that finding carries over to humans remains uncertain and continues to be monitored by researchers and regulators.

Reconstitution

The branded pens sold as Ozempic and Wegovy come pre-filled and ready to use; they are not reconstituted by the patient. This page instead covers the lyophilized (freeze-dried) semaglutide powder sold in 2 mg and 5 mg vials, which is typically reconstituted with bacteriostatic (BAC) water before use.

Worked example. A 5 mg vial is 5,000 mcg. Reconstituted with 2 mL of BAC water, that works out to 5,000 mcg ÷ 2 mL = 2,500 mcg/mL. On a U-100 insulin syringe, where each unit is 0.01 mL, each unit holds 2,500 × 0.01 = 25 mcg. A 2 mg vial with 1 mL comes out at 2,000 mcg/mL instead, or 20 mcg per unit. Use the peptide reconstitution calculator to work out the concentration and units for any vial size and water volume.

Important notes

Semaglutide is an FDA-approved prescription medicine, sold as Ozempic and Wegovy. The lyophilized vials discussed on this page are compounded or research-grade powder, a separate product from the branded, ready-to-use pens, and are not themselves FDA-approved products.

Frequently asked questions

These questions cover the same ground as the sections above, in a shorter format.

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