What Is in Ozempic Injection? Understanding Its Composition and Benefits

Last reviewed: June 26, 2026

Last updated: June 26, 2026

Written by: Jay Hastings, CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

Ozempic contains one active ingredient — semaglutide — dissolved in a short list of inactive ingredients that is not the same for every presentation. According to the Ozempic prescribing information (revised May 2026), each 1 mL of the multi-dose pen solution contains disodium phosphate dihydrate 1.42 mg, propylene glycol 14 mg, phenol 5.5 mg, and water for injections, at a pH of approximately 7.4. The single-dose prefilled syringes are formulated differently: each 1 mL contains disodium phosphate dihydrate 1.42 mg, sodium chloride 8.25 mg, and water for injection, with no phenol and no propylene glycol. Same active drug, two different vehicles, and the reason is worth understanding.

Semaglutide: What the Active Ingredient Actually Is

Semaglutide is a human glucagon-like peptide-1 (GLP-1) receptor agonist with 94% sequence homology to human GLP-1. Its peptide backbone is produced by yeast fermentation rather than extracted from a biological source, then chemically modified in three places. The label gives the molecular formula as C187H291N45O59 and the molecular weight as 4113.58 g/mol.

Those modifications are the whole engineering story. The main protraction mechanism is albumin binding, facilitated by modification of position 26 lysine with a hydrophilic spacer and a C18 fatty di-acid. Semaglutide is also modified at position 8 to stabilize it against degradation by the enzyme dipeptidyl peptidase 4 (DPP-4), the enzyme that clears native GLP-1 within minutes, plus a minor modification at position 34. Native GLP-1 has a half-life measured in minutes. Semaglutide's is approximately one week, which is why it is dosed once weekly rather than several times a day.

The label's pharmacokinetics section fills in the rest: absolute bioavailability is 89%, maximum concentration is reached 1 to 3 days after a dose, and steady-state exposure is achieved after 4 to 5 weeks of once-weekly administration. That last figure explains why the early weeks of treatment do not represent what the drug eventually does in the body.

Why the Inactive Ingredients Differ Between Presentations

Phenol appears in the multi-dose pens and not in the single-dose syringes because it functions as an antimicrobial preservative. A pen that is punctured once a week for several weeks needs one; a syringe used once and discarded does not. In its place, the single-dose presentation uses sodium chloride at 8.25 mg per mL as a tonicity agent. Disodium phosphate dihydrate is the buffer in both, holding pH near 7.4, and the label notes that hydrochloric acid or sodium hydroxide may be added to adjust pH.

This is not trivia. Ozempic's contraindications include a serious hypersensitivity reaction to semaglutide or to any of the excipients. A reaction attributed to one presentation is not automatically a reaction to the molecule, and that distinction belongs in a conversation with the prescriber who has your full history rather than in an internet search.

How Much Semaglutide Is in Each Container

The concentration is not constant across the product line. The label lists three single-patient-use pens: 2 mg/3 mL (0.68 mg/mL), 4 mg/3 mL (1.34 mg/mL), and 8 mg/3 mL (2.68 mg/mL). The single-dose prefilled syringes are supplied as 0.25 mg, 0.5 mg, or 1 mg per 0.5 mL — that is 0.5 mg/mL, 1 mg/mL, and 2 mg/mL respectively.

Each device is calibrated for the strength it holds. The volume delivered for a given dose is not the same across pens, which is one of several reasons the label directs patients to the Instructions for Use supplied with their specific presentation and to their prescriber, rather than to any general-purpose description of the product.

What Ozempic Is Approved to Treat

The prescribing information gives three indications, all in type 2 diabetes: as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus; to reduce the risk of major adverse cardiovascular events in adults with type 2 diabetes and established cardiovascular disease; and to reduce the risk of sustained eGFR decline, end-stage kidney disease, and cardiovascular death in adults with type 2 diabetes and chronic kidney disease.

There is no weight-management indication in the Ozempic label and no body mass index eligibility criterion anywhere in it. Semaglutide does hold an FDA approval for weight management — under the brand name Wegovy, on a separate application with its own trials and its own labeling. Same molecule, different products, and the distinction drives coverage decisions, prior authorization criteria, and what the evidence base actually supports.

The Benefits the Label Documents

Mechanistically, semaglutide selectively binds and activates the GLP-1 receptor, lowering blood glucose by stimulating insulin secretion and reducing glucagon in a glucose-dependent manner, with a secondary effect of delaying early gastric emptying. Glucose dependence is the point: the insulin response scales with the glucose signal, which is why the label's hypoglycemia warning is framed around concurrent insulin or insulin secretagogues rather than semaglutide alone.

The outcome data behind the two non-glycemic indications are specific. SUSTAIN 6 enrolled 3,297 adults with type 2 diabetes and atherosclerotic cardiovascular disease and reported a significant reduction in major adverse cardiovascular events, hazard ratio 0.74. FLOW enrolled 3,533 adults with type 2 diabetes and chronic kidney disease and reported a hazard ratio of 0.76 for the kidney composite outcome. Those are the trials the indications rest on.

The label is equally specific about what is common and unwelcome. Adverse reactions reported in at least 5% of treated patients are nausea, vomiting, diarrhea, abdominal pain, and constipation. In one placebo-controlled trial, nausea occurred in 15.8% of patients on 0.5 mg and 20.3% on 1 mg, versus 6.1% on placebo.

Compounded Semaglutide Is a Separate Formulation Question

A compounded semaglutide preparation is not an FDA-approved finished product, and the FDA does not review compounded drugs for safety, effectiveness, or quality before they are marketed. Its excipient list is set by the compounding pharmacy's formula, not by the Novo Nordisk label, so the ingredient list above does not describe it.

It is also not a generic version of Ozempic. No approved generic semaglutide exists, and describing a compounded preparation that way misstates both its regulatory status and the evidence behind it. What a compounded preparation is: a medication prepared by a licensed pharmacy pursuant to a prescription written for an individual patient. If you want to know exactly what is in a compounded vial, the pharmacy that prepared it is the only accurate source.

How Your Genetics Relate to GLP-1 Pathways

Not everyone responds to GLP-1 medications the same way. Genetic variants — including GIPR rs1800437, FTO rs9939609, and MC4R rs17782313 — relate to the biological pathways these medications act on. These are pathway-level associations only and do not predict how much weight you will lose or how you will respond to any specific medication. PlexusDx maps 14 pathways, 49 peptides, and 150+ genetic insights so you and your provider can see how your genes relate to these pathways. It does not recommend, prescribe, or determine which medication, dose, or peptide is right for you. The PlexusDx Precision Peptide Genetic Test ($298) gives you and your provider pathway-level genetic context to support a more personalized conversation. Genetics is a guide, not a guarantee.

Access Personalized GLP-1 Care Through PlexusDx

PlexusDx offers seven prescription GLP-1 protocols to all 50 states — no membership, no insurance required, async intake or live consult. Semaglutide Injection is $189/mo month-to-month, or from $149/mo on the 6-month plan. Medications are dispensed from licensed 503A compounding pharmacies following strict quality and safety standards. Add a Precision Peptide Genetic Test ($298) to personalize your protocol from day one.

Frequently Asked Questions

What is the active ingredient in Ozempic?

Semaglutide, a human GLP-1 receptor agonist with 94% sequence homology to human GLP-1. Its peptide backbone is produced by yeast fermentation and then modified at position 26 with a hydrophilic spacer and a C18 fatty di-acid, which drives albumin binding, and at position 8 to resist breakdown by the enzyme DPP-4. The label lists its molecular weight as 4113.58 g/mol.

What inactive ingredients does Ozempic contain?

It depends on the presentation. Each 1 mL of the multi-dose pen solution contains disodium phosphate dihydrate 1.42 mg, propylene glycol 14 mg, phenol 5.5 mg, and water for injections. Each 1 mL of the single-dose prefilled syringe solution contains disodium phosphate dihydrate 1.42 mg, sodium chloride 8.25 mg, and water for injection. Both sit at a pH of approximately 7.4.

Why does the Ozempic pen contain phenol?

Phenol acts as an antimicrobial preservative, which a multi-dose container needs because it is entered more than once over a period of weeks. The single-dose prefilled syringes are used once and discarded, so they contain no phenol and use sodium chloride as a tonicity agent instead. This is a routine formulation difference between multi-dose and single-dose injectable products.

Is Ozempic approved by the FDA for weight loss?

No. The Ozempic label carries three indications, all in type 2 diabetes: glycemic control, reduction of major adverse cardiovascular events in patients with established cardiovascular disease, and reduction of kidney and cardiovascular outcomes in patients with chronic kidney disease. There is no weight-management indication and no BMI criterion in the label. Wegovy is the semaglutide product approved for weight management.

Does compounded semaglutide have the same ingredients as Ozempic?

Not necessarily. A compounded preparation is not an FDA-approved finished product, and its inactive ingredients are determined by the compounding pharmacy's formula rather than by the Ozempic label. It is also not a generic version of Ozempic, since no approved generic semaglutide exists. The pharmacy that prepared a given compounded medication is the accurate source for its composition.

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.