Ozempic contains one active ingredient, semaglutide, along with a short list of inactive ingredients: disodium phosphate dihydrate, propylene glycol, phenol, water for injections, and small amounts of hydrochloric acid or sodium hydroxide to adjust the pH. That’s the complete formula. Each milliliter of solution contains 1.34 mg of semaglutide suspended in this simple mix of stabilizers and preservatives.
Semaglutide: The Active Ingredient
Semaglutide is a lab-made version of a hormone your gut naturally releases after you eat, called GLP-1 (glucagon-like peptide-1). The natural hormone helps regulate blood sugar, slows digestion, and signals fullness to your brain. The problem is that natural GLP-1 breaks down in the body within minutes. Semaglutide is engineered to last much longer, which is why a single weekly injection can work continuously for seven days.
Structurally, semaglutide is a peptide chain of 31 amino acids with the molecular formula C₁₈₇H₂₉₁N₄₅O₅₉. It works through several pathways at once. It increases insulin release in response to meals, lowering blood sugar. It suppresses glucagon, a hormone that raises blood sugar. It slows stomach emptying so food stays in your digestive system longer. And it acts on appetite centers in the brain to reduce hunger and increase feelings of fullness. That combination of effects is why Ozempic is approved for type 2 diabetes and why semaglutide (at a higher dose, branded as Wegovy) is also approved for weight management.
What Each Inactive Ingredient Does
The inactive ingredients in Ozempic aren’t there by accident. Each one serves a specific purpose in keeping the solution stable, sterile, and safe for injection. Here’s what’s in the mix and why.
- Disodium phosphate dihydrate (1.42 mg per mL) acts as a buffer, helping maintain a stable pH level in the solution. Injectable medications need to stay within a narrow pH range to remain effective and to avoid irritating tissue at the injection site.
- Propylene glycol (14 mg per mL) serves as a solvent and stabilizer. It helps keep semaglutide evenly distributed in the solution so each dose delivers a consistent amount of the active ingredient.
- Phenol (5.5 mg per mL) is a preservative. Because Ozempic pens are designed to deliver multiple doses over several weeks, phenol prevents bacterial growth in the solution after the pen has been used.
- Water for injections is the base of the solution. This is highly purified water that meets strict pharmaceutical standards for sterility.
- Hydrochloric acid or sodium hydroxide may be added in trace amounts during manufacturing to fine-tune the pH to the correct level.
Allergen and Sensitivity Considerations
The Ozempic formulation does not contain gluten or lactose. The pen’s cartridge is sealed with a glass container, an aluminum cap, and rubber components made from chlorobutyl and bromobutyl/polyisoprene. The FDA labeling does not identify natural rubber latex in the pen’s construction.
Phenol is worth noting if you have known sensitivities. It’s widely used as a preservative in injectable medications (including insulin), and the amount in Ozempic is small, but it can occasionally cause mild irritation at the injection site. Propylene glycol, while sometimes flagged as an allergen in topical products, is present in a very low concentration here and is generally well tolerated when injected.
How the Pen Delivers the Dose
Ozempic comes as a pre-filled, multi-dose pen. The solution inside the pen cartridge is clear and colorless. One common pen configuration holds 4 mg of semaglutide in 3 mL of solution, calibrated to deliver 1 mg per dose. Different pen sizes exist for the lower doses used during the initial weeks of treatment when your body is adjusting to the medication.
Before first use, pens need to be stored in a refrigerator between 36°F and 46°F. Once you start using a pen, it stays good for 56 days and can be kept either in the refrigerator or at room temperature (59°F to 86°F). If the solution has ever been exposed to temperatures below 36°F or above 86°F, it should not be used. The inactive ingredients, particularly the buffer and preservative system, are what allow the pen to remain stable at room temperature for those eight weeks of use.
Why the Formula Is So Simple
Compared to many injectable medications, Ozempic’s ingredient list is notably short. That simplicity is partly a reflection of semaglutide’s own stability. The molecule was designed with a fatty acid side chain that allows it to bind to albumin (a protein in your blood), which shields it from being broken down quickly. Because the active ingredient is inherently long-lasting and relatively stable, the formulation doesn’t require the complex cocktail of stabilizers that some other biologics need. The result is a lean formula: one active peptide, one preservative, one buffer, one solvent, and water.