Semaglutide

Semaglutide is a GLP-1 receptor agonist, a synthetic analog of glucagon-like peptide-1, an intestinal hormone released after eating. It binds to GLP-1 receptors in the brain, pancreas, and gut, producing three main effects: slowed gastric emptying (food stays in your stomach longer), reduced appetite signaling in the hypothalamus, and improved glucose-dependent insulin secretion. The net result is eating less without requiring willpower, because the physiological hunger signal is suppressed.

In the STEP-1 clinical trial, adults using semaglutide 2.4 mg weekly with lifestyle intervention lost an average of 14.9% body weight over 68 weeks, compared to 2.4% in the placebo group. The STEP-3 trial added intensive behavioral therapy and observed 16.0% loss. These are the largest weight-loss results ever recorded in a pharmaceutical trial at the time of publication. Semaglutide does not cause weight loss through stimulation, thermogenesis, or thyroid effects, it works purely by reducing caloric intake.

Reconstituting semaglutide requires bacteriostatic water (BAC water), not sterile water for injection. BAC water contains 0.9% benzyl alcohol as a preservative, allowing multi-draw use over 28 days. Add BAC water by injecting it slowly along the inside wall of the vial, then gently roll, never shake. Shaking can degrade the peptide. The calculator above handles all the math: enter your vial size, the amount of BAC water you added, and your desired dose to see exact syringe units.

Injection technique: use a 29–31 gauge insulin syringe (U-100, 1 mL). Common sites are the abdomen (at least 2 inches from the navel), outer thigh, or upper arm. Pinch the skin, insert at 45–90 degrees depending on subcutaneous fat depth, and inject slowly. Rotate sites each week. After drawing your dose, cap the vial and return it to the refrigerator. Reconstituted semaglutide is stable for up to 28 days at 2–8°C (36–46°F). Do not freeze, and discard if it appears cloudy or contains particles.

The most common side effects are gastrointestinal: nausea, constipation, and occasionally vomiting. These are almost always dose-dependent and improve as your body adjusts. Titrating slowly, spending at least 4 weeks at each dose level, dramatically reduces GI burden. Eating smaller meals, avoiding high-fat foods, and staying hydrated all help. Semaglutide is not associated with significant muscle loss when combined with adequate protein intake (0.8–1.2 g per pound of body weight) and resistance training.