Ozempic contains one active ingredient, semaglutide, plus four inactive ingredients: disodium phosphate dihydrate, propylene glycol, phenol, water for injections, and trace amounts of hydrochloric acid or sodium hydroxide to adjust pH. The solution is clear and colorless with a pH of approximately 7.4, close to your body’s natural pH.
The Active Ingredient: Semaglutide
Semaglutide is a lab-made version of a hormone your body naturally produces called GLP-1 (glucagon-like peptide-1). This hormone helps regulate blood sugar by signaling your pancreas to release insulin after you eat. It also slows stomach emptying and reduces appetite, which is why Ozempic has become widely known for its weight-related effects even though it’s approved specifically for type 2 diabetes.
The semaglutide molecule is built on a protein backbone produced through yeast fermentation, then chemically modified in three key places to make it last much longer than the natural hormone. One modification attaches a fatty acid chain that lets the drug latch onto a protein in your blood called albumin. This acts like an anchor, keeping semaglutide circulating in your body for about a week instead of being broken down in minutes. A second modification protects the molecule from an enzyme that would otherwise chop it apart quickly. A third ensures the fatty acid chain attaches in only one spot, keeping the drug consistent and predictable.
These engineering choices are what make a once-weekly injection possible. Natural GLP-1 is cleared from the body in about two minutes.
Inactive Ingredients and What They Do
Each milliliter of Ozempic solution contains small amounts of four inactive ingredients. They don’t treat anything on their own, but they keep the medication stable, sterile, and safe to inject.
- Phenol (5.5 mg per mL) serves as an antimicrobial preservative. Because Ozempic pens are used for multiple injections over several weeks, phenol prevents bacteria from growing in the solution between uses. It’s a standard preservative in injectable medications at concentrations between 0.5% and 1%.
- Propylene glycol (14 mg per mL) acts as a solvent and stabilizer, helping keep semaglutide evenly dissolved in the solution so each dose delivers a consistent amount of the drug.
- Disodium phosphate dihydrate (1.42 mg per mL) is a buffering agent. It helps maintain the solution’s pH at approximately 7.4, which matches your body’s natural pH and minimizes irritation at the injection site.
- Water for injections makes up the bulk of the liquid and serves as the base in which everything else is dissolved.
Small amounts of hydrochloric acid or sodium hydroxide may also be added during manufacturing to fine-tune the pH if needed. These aren’t listed as formal ingredients because they’re processing aids rather than fixed components of the formula.
Concentration Differences Between Pens
The active and inactive ingredients are the same across all Ozempic pens. What changes is the concentration of semaglutide. There are three pen strengths currently on the market:
- 2 mg per 3 mL (0.68 mg/mL): delivers either 0.25 mg or 0.5 mg per injection, used when starting treatment or at a lower maintenance dose
- 4 mg per 3 mL (1.34 mg/mL): delivers 1 mg per injection
- 8 mg per 3 mL (2.68 mg/mL): delivers 2 mg per injection, the highest available dose
Each pen is prefilled, disposable, and designed for a single patient. You select your dose using a dial on the pen rather than measuring the liquid yourself.
How Ozempic Compares to Wegovy
Wegovy contains the exact same active ingredient, semaglutide, made by the same manufacturer, Novo Nordisk. The core difference is the approved use and dosing range. Ozempic is approved for type 2 diabetes at doses up to 2 mg weekly, while Wegovy is approved for weight management at doses up to 2.4 mg weekly. If you’re comparing ingredient labels, the active molecule is identical.
Allergy Concerns With Ozempic Ingredients
Serious allergic reactions to Ozempic are rare but possible. They can be triggered by semaglutide itself or by any of the inactive ingredients. Reported reactions have included anaphylaxis (a severe, whole-body allergic response) and angioedema (swelling beneath the skin, often around the face and throat). If you’ve had a previous allergic reaction to semaglutide in any form, Ozempic is contraindicated.
Propylene glycol and phenol are both common in injectable medications and topical products, so most people have been exposed to them before without issue. However, if you know you’re sensitive to either compound, it’s worth flagging before starting treatment. Propylene glycol also appears in many foods, cosmetics, and medications, so a known sensitivity would likely already be on your radar.