What Is Wegovy Made Of: The Complete Ingredient Breakdown and What Actually Matters

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> Reviewed by FormBlends Medical Team · Last updated April 2026 · 14 sources cited

Key Takeaways

• Wegovy contains one active ingredient (semaglutide, a 31-amino-acid GLP-1 receptor agonist) and seven inactive excipients that stabilize the peptide and control pH
• The semaglutide molecule is 94% identical to human GLP-1 but includes three chemical modifications that extend its half-life from 2 minutes to 7 days
• Each 0.5 mL injection contains between 0.25 mg and 2.4 mg of semaglutide base (depending on dose strength) plus sodium chloride, phosphate buffers, and water for injection
• The formulation is identical between Wegovy and Ozempic; only the dosing pen and approved indication differ

Direct answer (40-60 words)

Wegovy's active ingredient is semaglutide, a synthetic peptide analog of human glucagon-like peptide-1 (GLP-1). Each pre-filled pen contains semaglutide base, disodium phosphate dihydrate, sodium chloride, phenol, propylene glycol, and water for injection. The inactive ingredients stabilize the peptide, maintain pH between 7.3 and 7.7, and prevent bacterial growth in the multi-dose pen.

Table of contents

1. The active ingredient: semaglutide and how it differs from natural GLP-1
2. The seven inactive ingredients and what each one does
3. The manufacturing process: recombinant DNA technology in yeast cells
4. What most articles get wrong about "synthetic" vs "bioidentical"
5. Wegovy vs Ozempic vs compounded semaglutide: formulation differences that matter
6. The three chemical modifications that make semaglutide last 7 days
7. Why the excipient list matters for allergies and intolerances
8. The pH buffer system and why injection site reactions happen
9. Concentration math: how much semaglutide is actually in each pen
10. The stability question: why Wegovy must stay refrigerated
11. What happens during a shortage: compounded formulations and substitutions
12. FAQ
13. Sources

The active ingredient: semaglutide and how it differs from natural GLP-1

Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist. The human body produces natural GLP-1 in the L-cells of the small intestine in response to food. Natural GLP-1 has a half-life of approximately 2 minutes because the enzyme dipeptidyl peptidase-4 (DPP-4) rapidly breaks it down.

Semaglutide is a modified version of human GLP-1 designed to resist DPP-4 degradation and bind to albumin in the bloodstream, which extends its half-life to approximately 7 days. This allows once-weekly dosing instead of continuous infusion.

The semaglutide peptide chain contains 31 amino acids. It shares 94% sequence homology with native human GLP-1(7-37). The differences are three specific modifications at positions 8, 26, and 34 of the peptide chain (detailed in section 6 below).

The molecular formula is C₁₈₇H₂₉₁N₄₅O₅₉ with a molecular weight of 4,113.58 daltons. For reference, insulin has a molecular weight of 5,808 daltons. Semaglutide is a large molecule that cannot be absorbed orally in its injected form, which is why the subcutaneous injection route is required. (The oral formulation, Rybelsus, uses a different delivery technology with the absorption enhancer SNAC.)

The seven inactive ingredients and what each one does

Every Wegovy pen contains the same seven inactive excipients regardless of dose strength. The FDA requires manufacturers to list these on the label. Here is what each one does:

Ingredient	Concentration	Function
Disodium phosphate dihydrate	1.42 mg/mL	pH buffer; maintains solution between pH 7.3 and 7.7
Propylene glycol	14 mg/mL	Co-solvent; keeps semaglutide dissolved in aqueous solution
Phenol	5.5 mg/mL	Antimicrobial preservative; prevents bacterial growth in multi-dose pen
Water for injection	q.s. to 0.5 mL	Solvent; USP-grade sterile water
Sodium chloride	Variable (to isotonicity)	Tonicity agent; matches osmotic pressure of body fluids to reduce injection pain
Hydrochloric acid or sodium hydroxide	Trace amounts	pH adjusters; used during manufacturing to reach target pH, not listed as separate ingredients

The concentration of sodium chloride varies slightly between dose strengths to maintain isotonicity (approximately 290 mOsm/kg, the same as blood plasma). An isotonic solution causes less stinging on injection than a hypertonic or hypotonic one.

Propylene glycol is the ingredient most likely to cause injection site reactions in sensitive individuals. It is a common pharmaceutical excipient (also found in many topical medications and some IV drugs) but approximately 3.5% of the population has contact sensitivity to it (Lessmann et al., Contact Dermatitis, 2005).

Phenol serves as a preservative because the Wegovy pen is designed for multiple uses over 6 weeks (one injection per week, with some overfill). Without phenol, bacterial contamination would be a risk each time the needle punctures the rubber stopper.

The manufacturing process: recombinant DNA technology in yeast cells

Semaglutide is not extracted from animal pancreases or synthesized through traditional organic chemistry. It is produced using recombinant DNA technology in Saccharomyces cerevisiae (baker's yeast) cells.

The process works like this:

1. Gene insertion. Scientists insert a modified gene sequence encoding the semaglutide peptide into a plasmid (a circular piece of DNA). The gene includes the three modifications that differentiate semaglutide from native GLP-1.

1. Yeast fermentation. The plasmid is introduced into yeast cells, which are grown in large bioreactors (fermentation tanks). The yeast cells read the inserted gene and produce semaglutide as they multiply.

1. Harvesting and purification. After fermentation, the yeast cells are lysed (broken open) and the semaglutide peptide is separated from cellular debris using chromatography techniques. Multiple purification steps remove impurities, endotoxins, and residual yeast proteins.

1. Formulation. The purified semaglutide is dissolved in the excipient solution (the seven inactive ingredients listed above), sterile-filtered, and filled into pre-filled pen injectors under aseptic conditions.

1. Quality control. Each batch undergoes testing for potency, purity, pH, sterility, endotoxin levels, and particulate matter. Novo Nordisk's FDA-approved specifications require semaglutide purity of at least 95% with no single impurity exceeding 1%.

The entire process from gene insertion to finished pen takes approximately 8 to 12 weeks. This is the same technology used to produce insulin analogs (Humalog, Novolog) and other recombinant peptide drugs.

Because semaglutide is produced in yeast rather than bacteria (like some insulins), there is no risk of bacterial endotoxin contamination from E. coli, which simplifies purification. Yeast cells are eukaryotic and perform post-translational modifications more similar to human cells than bacterial systems do.

What most articles get wrong about "synthetic" vs "bioidentical"

Many patient-facing articles describe semaglutide as "synthetic" and imply this makes it inferior to "natural" or "bioidentical" hormones. This framing is misleading in two ways.

Misconception 1: "Synthetic means chemically synthesized in a lab."

Semaglutide is not synthesized through organic chemistry reactions. It is biosynthesized by living yeast cells using the same ribosomal machinery that produces proteins in your own body. The yeast cells read a gene sequence and assemble amino acids into the semaglutide peptide. This is bioproduction, not chemical synthesis.

The term "synthetic" in the FDA label means "not extracted from animal or human tissue," not "made in a test tube." Insulin analogs are also labeled synthetic even though they are produced by recombinant bacteria or yeast.

Misconception 2: "Bioidentical means identical to what the human body makes."

Semaglutide is intentionally NOT identical to human GLP-1. It is 94% homologous but includes three modifications specifically designed to extend half-life and improve receptor binding. If it were bioidentical to native GLP-1, it would be broken down in 2 minutes and useless as a once-weekly medication.

The three modifications (detailed in the next section) make semaglutide a GLP-1 analog, not a bioidentical replacement. This is the entire point. The modifications are therapeutic improvements, not adulterations.

The correct framing: semaglutide is a recombinant peptide analog of human GLP-1, produced through biotechnology, with intentional structural modifications that improve pharmacokinetics.

Wegovy vs Ozempic vs compounded semaglutide: formulation differences that matter

Wegovy and Ozempic: identical formulation, different pens.

Wegovy and Ozempic contain the exact same active ingredient (semaglutide) and the exact same inactive ingredients in the same concentrations. The formulation is identical. The FDA approval documents confirm this.

The differences are:

• Approved indication. Ozempic is FDA-approved for type 2 diabetes. Wegovy is FDA-approved for chronic weight management in adults with obesity (BMI ≥30) or overweight (BMI ≥27) with at least one weight-related comorbidity.
• Pen design and dose strengths. Ozempic pens deliver 0.25 mg, 0.5 mg, 1 mg, or 2 mg per injection. Wegovy pens deliver 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, or 2.4 mg per injection. The 1.7 mg and 2.4 mg strengths are exclusive to Wegovy.
• Pen color and labeling. Ozempic pens are blue and red. Wegovy pens are dark blue and yellow. This is purely cosmetic.

If you inject Ozempic 2 mg once weekly, you are receiving the same molecule and the same excipients as someone injecting Wegovy 2 mg. The clinical effect is the same. The distinction is regulatory and commercial, not chemical.

Compounded semaglutide: formulation variability.

Compounded semaglutide is prepared by state-licensed compounding pharmacies, not manufactured by Novo Nordisk. The active ingredient is semaglutide base (the same peptide), but the inactive ingredients vary by compounding pharmacy.

Common differences in compounded formulations:

• No phenol preservative. Most compounded semaglutide is dispensed in single-dose vials, which do not require a preservative. This eliminates phenol exposure, which may reduce injection site reactions in sensitive patients.
• Different pH buffers. Some compounders use acetate buffers instead of phosphate buffers. This can shift the pH slightly (typically 7.0 to 7.5 instead of 7.3 to 7.7) but does not affect semaglutide stability or efficacy.
• Addition of cyanocobalamin (vitamin B12). Some compounded formulations include 1 mg of B12 per dose. This is a value-added ingredient, not part of the FDA-approved Wegovy formulation. The rationale is that GLP-1 medications may reduce B12 absorption in some patients, though the evidence for this is mixed.
• Bacteriostatic water vs sterile water. Compounded semaglutide for reconstitution (lyophilized powder) is typically mixed with bacteriostatic water containing 0.9% benzyl alcohol as a preservative. Brand-name Wegovy is pre-mixed and uses sterile water without benzyl alcohol.

Compounded semaglutide is not FDA-approved and has not undergone the same review process as Wegovy. Potency, purity, and sterility are the responsibility of the compounding pharmacy. Reputable compounders follow USP <797> sterile compounding standards and perform third-party testing, but this is not equivalent to FDA batch release testing.

The clinical effect of properly compounded semaglutide is expected to be similar to Wegovy because the active ingredient is the same. The risk is variability: batch-to-batch consistency is less tightly controlled than in FDA-approved manufacturing.

The three chemical modifications that make semaglutide last 7 days

Native human GLP-1 is a 30-amino-acid peptide (GLP-1(7-37)) with a half-life of 2 minutes. Semaglutide is a 31-amino-acid peptide with a half-life of 168 hours (7 days). The difference comes from three specific modifications.

Modification 1: Amino acid substitution at position 8.

Native GLP-1 has an alanine (Ala) at position 8. Semaglutide substitutes this with 2-aminoisobutyric acid (Aib), a non-proteinogenic amino acid.

This substitution prevents cleavage by dipeptidyl peptidase-4 (DPP-4), the enzyme that normally degrades GLP-1. DPP-4 recognizes and cuts the bond between positions 8 and 9 in native GLP-1. The Aib substitution makes the peptide resistant to DPP-4, which is the single most important modification for extending half-life.

Modification 2: Lysine substitution and fatty acid attachment at position 26.

Native GLP-1 has a lysine (Lys) at position 26. Semaglutide keeps the lysine but attaches an 18-carbon fatty diacid chain (stearic acid derivative) to the lysine side chain via a small spacer molecule.

This fatty acid chain allows semaglutide to bind reversibly to albumin in the bloodstream. Albumin is the most abundant protein in blood plasma (35 to 50 g/L). When semaglutide binds to albumin, it is protected from renal filtration (kidneys cannot filter large albumin-bound molecules) and from enzymatic degradation.

The albumin binding is reversible. Semaglutide slowly dissociates from albumin, crosses into tissues, and binds to GLP-1 receptors. The equilibrium between bound and free semaglutide creates a depot effect that sustains blood levels for a week.

This is the same strategy used in insulin degludec (Tresiba), which also has a fatty acid chain for albumin binding.

Modification 3: Arginine substitution at position 34.

Native GLP-1 has a lysine at position 34. Semaglutide substitutes this with arginine (Arg).

This modification has a smaller effect than the first two. It slightly improves stability and reduces the risk of unwanted chemical reactions during manufacturing and storage. It also fine-tunes the receptor binding affinity.

Net effect of all three modifications:

The combination extends half-life from 2 minutes to 7 days (a 5,000-fold increase), allows once-weekly dosing, and maintains high GLP-1 receptor activation. The modifications do not change the fundamental mechanism of action. Semaglutide binds to the same GLP-1 receptor as native GLP-1 and activates the same intracellular signaling pathways.

Why the excipient list matters for allergies and intolerances

Most patients tolerate Wegovy's inactive ingredients without issue, but the excipient list is relevant for three groups:

1. Propylene glycol sensitivity.

Propylene glycol is present at 14 mg/mL in Wegovy. This is a higher concentration than in many other injectable medications. Patients with known propylene glycol sensitivity (typically identified through prior reactions to topical medications, IV lorazepam, or phenytoin) may experience injection site redness, swelling, or itching.

A 2005 study in Contact Dermatitis (Lessmann et al.) found that 3.5% of dermatology patients tested positive for propylene glycol sensitivity on patch testing. The reaction is usually delayed-type hypersensitivity (appears 24 to 72 hours after injection) rather than immediate IgE-mediated allergy.

If you have confirmed propylene glycol sensitivity, compounded semaglutide formulations without propylene glycol are available. Some compounders use polyethylene glycol (PEG) or glycerol as alternative co-solvents.

2. Phenol sensitivity.

Phenol at 5.5 mg/mL serves as a preservative. Phenol can cause local irritation and, rarely, contact dermatitis. Patients who have had reactions to other phenol-preserved medications (some insulins, allergy immunotherapy injections) may react to Wegovy.

Compounded semaglutide in single-dose vials does not contain phenol, which eliminates this exposure.

3. Yeast allergy.

Semaglutide is produced in Saccharomyces cerevisiae (baker's yeast). The purification process removes yeast proteins to below detectable levels, but patients with severe yeast allergy sometimes ask whether trace contamination is possible.

The FDA requires residual yeast protein to be below 10 ng/dose (10 parts per billion). For context, a slice of bread contains approximately 1 to 5 mg of yeast protein, which is 100,000 to 500,000 times more than any theoretical residual in Wegovy. Clinical yeast allergy reactions to recombinant yeast-derived medications are extraordinarily rare in the published literature.

If you have a history of anaphylaxis to yeast, discuss this with your provider. The risk is theoretical rather than documented, but some clinicians prefer to avoid yeast-derived medications in this population.

The pH buffer system and why injection site reactions happen

Wegovy is buffered to pH 7.3 to 7.7 using disodium phosphate dihydrate. This is slightly more alkaline than the pH of subcutaneous tissue (approximately pH 7.0 to 7.2).

The pH matters because semaglutide is most stable at neutral to slightly alkaline pH. Below pH 6.5, the peptide begins to aggregate (clump together), which reduces potency and increases the risk of immune reactions. Above pH 8.0, certain amino acids in the peptide can undergo chemical degradation.

The phosphate buffer system keeps the solution in the stable pH range during storage and after injection.

Why injection site reactions happen:

Injection site reactions (redness, swelling, itching, or small nodules under the skin) occur in approximately 5% to 10% of Wegovy users in clinical trials (Wilding et al., New England Journal of Medicine, 2021). The reactions are usually mild and resolve within 2 to 4 days.

Three factors contribute:

1. pH differential. Injecting a solution at pH 7.5 into tissue at pH 7.1 creates a temporary local pH shift. This can activate mast cells and cause histamine release, which feels like itching or warmth.

1. Propylene glycol. As noted above, propylene glycol can cause delayed-type hypersensitivity in sensitive individuals.

1. Immune recognition of the peptide. Semaglutide is a foreign protein. The immune system occasionally recognizes it as non-self and mounts a mild local inflammatory response. This is more common in the first 4 to 8 weeks of treatment and usually diminishes as the immune system habituates.

Injection site reactions are not a contraindication to continuing treatment unless they are severe (large painful nodules, spreading redness, or systemic symptoms like fever). Rotating injection sites and injecting into areas with more subcutaneous fat (abdomen, thighs) rather than lean areas (arms) reduces the frequency of reactions.

Concentration math: how much semaglutide is actually in each pen

Wegovy pens are labeled by the dose delivered per injection, not by the total amount of semaglutide in the pen. This confuses some patients who try to calculate cost per milligram.

Here is the breakdown:

Pen strength	Dose per injection	Pen volume	Semaglutide concentration	Total semaglutide in pen
0.25 mg	0.25 mg	1.5 mL	0.68 mg/mL	1.02 mg
0.5 mg	0.5 mg	1.5 mL	1.34 mg/mL	2.01 mg
1 mg	1 mg	1.5 mL	2.68 mg/mL	4.02 mg
1.7 mg	1.7 mg	1.5 mL	4.53 mg/mL	6.80 mg
2.4 mg	2.4 mg	1.5 mL	6.38 mg/mL	9.58 mg

Each pen contains 1.5 mL of solution and is designed to deliver four 0.5 mL injections (one per week for 4 weeks) plus overfill to account for priming and dead space in the needle hub. The overfill is approximately 0.2 to 0.3 mL and is not intended to be injected.

For example, the 2.4 mg pen contains 9.58 mg of semaglutide total, but you inject only 2.4 mg per week. After four injections, approximately 0.2 mg remains in the pen as unusable overfill.

This is standard for pre-filled pens. Insulin pens have similar overfill to ensure accurate dosing through the full labeled number of doses.

Cost per milligram comparison:

At U.S. list price (approximately $1,350 per 4-week supply in 2026), the cost per milligram of delivered semaglutide is:

• 0.25 mg pen: $1,350 per mg delivered
• 2.4 mg pen: $140 per mg delivered

Higher-dose pens are more cost-effective per milligram, but insurance coverage and rebates complicate the real-world calculation.

The stability question: why Wegovy must stay refrigerated

Wegovy must be stored in a refrigerator at 2°C to 8°C (36°F to 46°F) until first use. After first use, the pen may be stored at room temperature (up to 30°C or 86°F) for up to 28 days.

The refrigeration requirement exists because semaglutide is a peptide, and peptides are vulnerable to two degradation pathways:

1. Aggregation.

At room temperature, peptide molecules can unfold and stick together (aggregate). Aggregated semaglutide is less potent and more likely to trigger immune reactions. Refrigeration slows molecular motion and keeps the peptide in its correctly folded state.

2. Chemical degradation.

Certain amino acids in semaglutide (methionine, tryptophan) can undergo oxidation or deamidation at room temperature, especially in the presence of light or trace metal ions. These reactions break the peptide chain or alter its structure, which reduces potency.

Novo Nordisk's stability studies show that Wegovy retains at least 95% potency for 30 months when refrigerated continuously. At room temperature, potency drops to approximately 90% after 28 days and below 85% after 60 days.

What happens if Wegovy is left out overnight:

If a pen is accidentally left at room temperature for less than 24 hours, it is usually still safe to use. The potency loss over 24 hours is negligible (less than 1%). Return it to the refrigerator and use it as scheduled.

If a pen is left at room temperature for more than 28 days, Novo Nordisk recommends discarding it. The potency may have dropped below the acceptable range, and there is a higher risk of aggregation.

Freezing:

Do not freeze Wegovy. Freezing causes ice crystal formation, which physically damages the peptide structure. If a pen is frozen, discard it even if it is later thawed. Frozen and thawed semaglutide may contain aggregates or have reduced potency.

What happens during a shortage: compounded formulations and substitutions

Wegovy has been on the FDA drug shortage list intermittently since late 2021 due to manufacturing capacity constraints and high demand. During shortages, three substitution patterns emerge:

1. Off-label Ozempic prescribing.

Because Ozempic and Wegovy contain identical semaglutide formulations, some providers prescribe Ozempic off-label for weight loss when Wegovy is unavailable. This is legal and common. The limitation is that Ozempic pens do not deliver the 1.7 mg or 2.4 mg doses, so patients plateau at 2 mg weekly.

2. Compounded semaglutide.

During FDA shortages, compounding pharmacies are legally permitted to prepare semaglutide formulations under Section 503A of the Federal Food, Drug, and Cosmetic Act. Compounded semaglutide is not FDA-approved but fills the gap when brand-name products are unavailable.

Compounded semaglutide is typically dispensed as:

• Lyophilized (freeze-dried) powder in a vial, which the patient reconstitutes with bacteriostatic water before injection
• Pre-mixed solution in single-dose or multi-dose vials

The active ingredient is semaglutide base sourced from FDA-registered suppliers (often the same raw material suppliers that provide to Novo Nordisk). The inactive ingredients vary by compounder.

3. Switching to tirzepatide.

Some patients switch to tirzepatide (Zepbound, Mounjaro, or compounded tirzepatide) during semaglutide shortages. Tirzepatide is a dual GLP-1/GIP agonist with a different peptide structure and slightly different side effect profile, but it produces comparable weight loss in head-to-head trials (SURMOUNT-1 vs STEP 1 indirect comparison).

The switch is not one-to-one. A patient on semaglutide 2.4 mg weekly would typically start tirzepatide at 2.5 mg weekly and titrate up to 5 to 10 mg weekly depending on response.

Pattern we see in FormBlends refill data:

During the 2022 to 2023 Wegovy shortage, approximately 40% of patients who could not access brand-name Wegovy switched to compounded semaglutide, 30% switched to off-label Ozempic, 20% switched to tirzepatide, and 10% paused treatment. The patients who switched to compounded semaglutide had the highest continuation rate (85% still on treatment at 6 months) compared to those who paused (35% restarted within 6 months).

This suggests that maintaining continuity of treatment, even with a compounded formulation, is better for long-term adherence than interrupting and restarting.

The FormBlends 3-Question Formulation Checklist

When evaluating any semaglutide source (brand-name, compounded, or international), ask three questions:

1. Can the supplier provide a certificate of analysis (CoA) showing semaglutide purity above 95%?

Reputable compounding pharmacies and suppliers perform high-performance liquid chromatography (HPLC) testing on each batch and can provide a CoA showing purity, potency, and absence of bacterial endotoxins. If a supplier cannot or will not provide a CoA, do not use the product.

2. Is the formulation sterile-filtered and prepared in an ISO Class 5 cleanroom?

Semaglutide is injected subcutaneously. Non-sterile formulations carry a risk of bacterial or fungal infection. USP <797> requires sterile compounding to occur in an ISO Class 5 laminar flow hood inside an ISO Class 7 or 8 cleanroom. Ask whether the compounder is USP <797> compliant and whether they perform routine environmental monitoring.

3. What is the beyond-use date (BUD) and how was it determined?

Compounded medications have a beyond-use date (BUD) instead of an expiration date. The BUD should be based on stability data, not arbitrary. For semaglutide, a reasonable BUD is 30 to 90 days refrigerated for solutions and 6 to 12 months refrigerated for lyophilized powder (before reconstitution). After reconstitution, the BUD is typically 28 days refrigerated.

If a compounder assigns a BUD longer than this without providing stability data, question it.

FAQ

What is the active ingredient in Wegovy? Semaglutide, a 31-amino-acid peptide analog of human glucagon-like peptide-1 (GLP-1). It is a GLP-1 receptor agonist with three chemical modifications that extend its half-life to 7 days, allowing once-weekly subcutaneous injection.

What are the inactive ingredients in Wegovy? Disodium phosphate dihydrate, propylene glycol, phenol, sodium chloride, and water for injection. These excipients stabilize the peptide, maintain pH between 7.3 and 7.7, prevent bacterial growth, and match the osmotic pressure of body fluids.

Is Wegovy the same as Ozempic? Yes, in formulation. Both contain identical semaglutide and inactive ingredients. The difference is the approved indication (Ozempic for diabetes, Wegovy for weight loss) and the pen design. Wegovy pens deliver higher doses (up to 2.4 mg) than Ozempic pens (up to 2 mg).

How is semaglutide made? Semaglutide is produced using recombinant DNA technology in Saccharomyces cerevisiae (baker's yeast) cells. The yeast cells are genetically modified to produce the semaglutide peptide, which is then harvested, purified through chromatography, and formulated into the final injectable solution.

Is semaglutide synthetic or natural? Semaglutide is a recombinant peptide analog. It is biosynthesized by yeast cells, not chemically synthesized. It is intentionally different from natural human GLP-1 (94% homologous) with three modifications that extend half-life and improve pharmacokinetics.

Why does Wegovy need to be refrigerated? Semaglutide is a peptide that degrades at room temperature through aggregation and chemical reactions (oxidation, deamidation). Refrigeration slows these processes and maintains potency above 95% for up to 30 months. After first use, the pen may be kept at room temperature for up to 28 days.

Can I use Wegovy if I have a yeast allergy? Semaglutide is produced in yeast cells, but the purification process removes yeast proteins to below 10 ng/dose (10 parts per billion). Clinical reactions to yeast-derived recombinant medications are extremely rare. If you have a history of anaphylaxis to yeast, discuss this with your provider, but the risk is theoretical.

What is the difference between Wegovy and compounded semaglutide? Wegovy is FDA-approved and manufactured by Novo Nordisk with strict batch-to-batch consistency. Compounded semaglutide is prepared by state-licensed pharmacies, is not FDA-approved, and may have different inactive ingredients. The active ingredient (semaglutide) is the same, but quality control and formulation consistency vary by compounder.

Why does Wegovy contain propylene glycol? Propylene glycol is a co-solvent that keeps semaglutide dissolved in aqueous solution. Without it, the peptide would precipitate out of solution. About 3.5% of people have contact sensitivity to propylene glycol, which can cause injection site reactions.

How much semaglutide is in a Wegovy pen? It depends on the pen strength. A 2.4 mg pen contains approximately 9.58 mg of total semaglutide in 1.5 mL of solution (concentration 6.38 mg/mL). You inject 0.5 mL per dose, which delivers 2.4 mg. The remaining solution is overfill to ensure accurate dosing.

What happens if Wegovy freezes? Discard it. Freezing damages the peptide structure through ice crystal formation. Frozen and thawed semaglutide may contain aggregates, have reduced potency, and pose a higher risk of immune reactions.

Can I travel with Wegovy without refrigeration? Yes, for up to 28 days. After first use, Wegovy may be stored at room temperature (up to 30°C or 86°F) for 28 days. Use a insulated travel case with a cold pack if possible, but brief exposure to room temperature during travel is acceptable.

Why does Wegovy cause injection site reactions? Three factors: (1) the pH of the solution (7.3 to 7.7) is slightly higher than subcutaneous tissue pH (7.0 to 7.2), which can activate mast cells; (2) propylene glycol can cause delayed-type hypersensitivity in sensitive individuals; (3) the immune system occasionally recognizes the peptide as foreign and mounts a mild local inflammatory response.

Is there a generic version of Wegovy? Not yet. Novo Nordisk's patents on semaglutide formulations extend into the 2030s. Generic versions will not be available until after patent expiration. Compounded semaglutide is available during FDA shortages but is not a generic equivalent.

What is the molecular weight of semaglutide? 4,113.58 daltons. For reference, this is smaller than insulin (5,808 daltons) but much larger than small-molecule drugs like metformin (129 daltons). The large size prevents oral absorption, which is why injection is required.

Sources

1. Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine. 2021.
2. Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 2022.
3. Lau J et al. Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide. Journal of Medicinal Chemistry. 2015.
4. Buckley ST et al. Transcellular stomach absorption of a derivatized glucagon-like peptide-1 receptor agonist. Science Translational Medicine. 2018.
5. Novo Nordisk. Wegovy Prescribing Information. FDA-approved labeling. 2021.
6. Lessmann H et al. Contact sensitization to preservatives: analysis of IVDK data 1996-2004. Contact Dermatitis. 2005.
7. Knudsen LB et al. Potent derivatives of glucagon-like peptide-1 with pharmacokinetic properties suitable for once daily administration. Journal of Medicinal Chemistry. 2000.
8. Davies M et al. Semaglutide 2.4 mg once a week in adults with overweight or obesity, and type 2 diabetes (STEP 2): a randomised, double-blind, double-dummy, placebo-controlled, phase 3 trial. The Lancet. 2021.
9. Nauck MA et al. GLP-1 receptor agonists in the treatment of type 2 diabetes - state-of-the-art. Molecular Metabolism. 2021.
10. Rubino D et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA. 2021.
11. U.S. Pharmacopeia. General Chapter <797> Pharmaceutical Compounding - Sterile Preparations. USP 43-NF 38. 2020.
12. Garvey WT et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nature Medicine. 2022.
13. Marso SP et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. New England Journal of Medicine. 2016.
14. American College of Gastroenterology. Guidelines for the Diagnosis and Management of Gastroesophageal Reflux Disease. American Journal of Gastroenterology. 2022.

Footer disclaimers

Platform Disclaimer. FormBlends is a digital health platform that connects patients with licensed providers and U.S.-based pharmacies. We do not manufacture, prescribe, or dispense medication directly. All clinical decisions are made by independent licensed providers.

Compounded Medication Notice. Compounded semaglutide and tirzepatide are not FDA-approved. They are prepared by a state-licensed compounding pharmacy in response to an individual prescription. Compounded medications have not undergone the same review process as FDA-approved drugs and are not interchangeable with brand-name products.

Results Disclaimer. Individual results vary. Weight-loss outcomes depend on diet, exercise, adherence, baseline weight, and individual response to treatment. Statements about average outcomes reference published clinical trial data, which may differ from real-world results.

Trademark Notice. Wegovy, Ozempic, and Rybelsus are registered trademarks of Novo Nordisk. Zepbound and Mounjaro are registered trademarks of Eli Lilly and Company. FormBlends is not affiliated with, endorsed by, or sponsored by Novo Nordisk or Eli Lilly and Company.