Last medically reviewed: 2026-04-27 by GLP3 Planner editorial. References inline as available.

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Key Takeaways

Standard concentration: Mix 5mg semaglutide with 2-2.5mL BAC water for easy dosing
Injection technique: Add water slowly down the vial wall, never directly onto powder
Mixing method: Gently swirl (never shake) until fully dissolved
Storage: Refrigerate at 36-46°F (2-8°C) for up to 28-56 days
Use our free calculator to determine exact insulin units for your dose
Switching from a Wegovy or Ozempic pen? The pen-to-vial calculator converts your weekly pen dose into the units to draw from your vial, with switch-week timing

📋 Note: This guide is for compounded semaglutide (lyophilized powder). Brand-name products like Ozempic and Wegovy come as pre-filled pens and don't require reconstitution. Compounded semaglutide is often more affordable but requires proper mixing.

What is Reconstitution?

Reconstitution means adding bacteriostatic water (BAC water) to freeze-dried (lyophilized) peptide powder to make an injectable solution. Compounded semaglutide comes as a white powder in a sealed vial that you mix before use.

Unlike pre-filled Ozempic or Wegovy pens, compounded semaglutide requires you to:

Calculate how much BAC water to add for your desired concentration
Properly mix the solution without damaging the peptide
Store the reconstituted solution correctly
Calculate the right volume (in insulin units) for each dose

Our free reconstitution calculator handles the math. Enter your vial size, water volume, and desired dose.

What You'll Need

Semaglutide reconstitution supplies including peptide vial, bacteriostatic water, and syringe — Standard supplies for semaglutide reconstitution

Required Supplies

✓ Semaglutide vial (lyophilized powder, typically 3mg, 5mg, or 10mg)
✓ Bacteriostatic water (BAC water): contains 0.9% benzyl alcohol as preservative
✓ Insulin syringes (U-100, 0.5mL or 1mL with fine gauge needle)
✓ Alcohol swabs (70% isopropyl alcohol)

Optional but Recommended

○ Larger mixing syringe (3mL) for adding BAC water
○ Sharps container for safe needle disposal
○ Clean workspace with good lighting
○ Vial labels to mark reconstitution date and concentration

⚠️ Do NOT use: Sterile water or saline without preservative. These lack the benzyl alcohol that prevents bacterial growth. Always use bacteriostatic water for multi-dose vials.

Semaglutide Reconstitution Calculator

Before mixing, use our calculator to determine the right BAC water volume and how many insulin units equal your desired dose.

Free Reconstitution Calculator

Enter your vial size, BAC water volume, and desired dose to get exact insulin units.

Reconstitution Chart Calculator → Save Your Vial (Log In) →

Quick Reference: Common Concentrations

Vial Size	BAC Water	Concentration	0.25mg Dose	0.5mg Dose	1mg Dose
3mg	1.5mL	2mg/mL	12.5 IU	25 IU	50 IU
5mg	2mL	2.5mg/mL	10 IU	20 IU	40 IU
5mg	2.5mL	2mg/mL	12.5 IU	25 IU	50 IU
10mg	2mL	5mg/mL	5 IU	10 IU	20 IU

IU = insulin units on a U-100 syringe (100 IU = 1mL). Use our calculator for custom concentrations.

Step-by-Step Reconstitution Instructions

Step-by-step peptide reconstitution process showing BAC water injection technique — Proper technique: inject BAC water slowly down the vial wall

Prepare Your Workspace

Wash your hands thoroughly. Gather all supplies on a clean, flat surface with good lighting. Allow the vial and BAC water to reach room temperature if refrigerated.

Clean the Vial Tops

Wipe the rubber stopper of both the semaglutide vial and BAC water vial with an alcohol swab. Let the alcohol dry completely (about 10-15 seconds) before proceeding.

Draw the BAC Water

Using a syringe, draw the calculated amount of BAC water. For a 5mg vial, 2-2.5mL is typical. Pull back the plunger slightly to add air first, inject air into the BAC water vial, then withdraw the water.

⚠️ Inject Water SLOWLY Down the Vial Wall

This is the step people mess up most. Insert the needle into the semaglutide vial and angle it so the tip touches the glass wall. Inject the BAC water very slowly, letting it run down the side of the vial. Don't spray it directly onto the powder.

Direct force on the powder can damage the peptide structure and reduce potency. A slow stream down the wall keeps the molecule intact.

Gently Swirl to Dissolve

Never shake the vial. Gently swirl it in a circular motion to help the powder dissolve. You can also let it sit for a few minutes and swirl again. The solution should become clear with no visible particles.

Dissolution typically takes 1-5 minutes. Semaglutide dissolves readily; if cloudiness persists after 10 minutes of gentle swirling, contact your supplier.

Label and Store

Write the reconstitution date, concentration, and expiration date on the vial. Store immediately in the refrigerator at 36-46°F (2-8°C).

Video Tutorial

Watch this step-by-step demonstration of peptide reconstitution and injection technique by Dr. Jason Emer:

Video covers: supplies needed, sterile technique, BAC water injection, mixing, and subcutaneous injection demonstration.

Semaglutide Dosing Reference

Standard semaglutide titration starts at 0.25mg weekly and increases every 4 weeks. Use our semaglutide calculator to plan your entire protocol and visualize drug levels.

Tier	Weekly Dose	Duration	Notes
1	0.25 mg	4 weeks	Titration dose
2	0.5 mg	4 weeks	Titration dose
3	1.0 mg	4+ weeks	Ozempic maintenance
4	1.7 mg	4 weeks	Wegovy only
5	2.4 mg	Maintenance	Wegovy maintenance

💡 Tip: Semaglutide has a 7-day half-life (the longest among GLP-1s), meaning it takes 4-5 weeks to reach steady state at each dose tier. Don't increase too quickly.

Storage After Reconstitution

Proper peptide storage in refrigerator at 36-46°F — Store reconstituted peptides in the refrigerator at 36-46°F (2-8°C)

✓ Do This

• Store in refrigerator at 36-46°F (2-8°C)
• Keep away from light (store in box if possible)
• Use within 28-56 days of reconstitution
• Inspect for particles before each use
• Always swab the stopper before drawing

✗ Never Do This

• Never freeze reconstituted semaglutide
• Don't leave at room temperature for extended periods
• Don't use if solution is cloudy or has particles
• Don't use past the expiration date
• Never share vials or needles

Stability note: Semaglutide is generally more stable than some other peptides. Many compounding pharmacies cite 56-day stability, but 28 days is the conservative recommendation. Potency may decrease over time.

Common Mistakes to Avoid

❌ Spraying water directly onto the powder

High-pressure streams can denature (damage) the peptide. Always aim for the vial wall and let the water run down gently.

❌ Shaking the vial

Vigorous shaking creates foam and can damage the peptide structure. Gentle swirling is all that's needed.

❌ Using sterile water instead of BAC water

Sterile water has no preservative, so bacteria can grow in multi-dose vials. BAC water's benzyl alcohol prevents contamination.

❌ Confusing Ozempic/Wegovy pre-fills with compounded vials

Brand-name semaglutide comes in ready-to-use pens. Only compounded lyophilized semaglutide requires reconstitution. Never try to add water to a pre-filled pen.

❌ Reusing needles

Reused needles become dull, cause more pain, and increase infection risk. Use a new sterile needle for each injection.

Frequently Asked Questions

How much bacteriostatic water should I use to reconstitute semaglutide?

For a 5mg semaglutide vial, 2-2.5mL of bacteriostatic water is standard. Using 2mL gives you 2.5mg/mL concentration (20 IU = 0.5mg), while 2.5mL gives 2mg/mL (25 IU = 0.5mg). The choice depends on your syringe size and dosing preferences. Use our reconstitution calculator to determine the exact insulin units for any concentration.

How long does reconstituted semaglutide last?

Reconstituted semaglutide typically remains stable for 28-56 days when stored properly in the refrigerator at 36-46°F (2-8°C). Semaglutide is known for good stability, but the conservative recommendation is 28 days. Always label your vial with the reconstitution date and discard if the solution becomes cloudy or develops particles.

Is compounded semaglutide the same as Ozempic or Wegovy?

Compounded semaglutide contains the same active molecule as Ozempic and Wegovy, with the same 7-day half-life and mechanism of action. However, compounded versions come as lyophilized powder requiring reconstitution, while brand-name products come in pre-filled pens. Compounded semaglutide is not FDA-approved and may vary in quality between suppliers.

Can I freeze reconstituted semaglutide?

No, you should never freeze reconstituted semaglutide. Freezing can damage the peptide structure and reduce potency. Unreconstituted (powder) semaglutide can be stored frozen for longer-term storage, but once mixed with BAC water, refrigeration only.

What's the difference between bacteriostatic water and sterile water?

Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which inhibits bacterial growth and allows for multiple uses from the same vial. Sterile water has no preservative and is intended for single-use only. For multi-dose peptide vials like semaglutide, always use bacteriostatic water to prevent contamination.

How do I calculate insulin units for my semaglutide dose?

The formula is: Insulin Units = (Desired Dose in mg ÷ Concentration in mg/mL) × 100. For example, if you have 2.5mg/mL concentration and want a 0.5mg dose: (0.5 ÷ 2.5) × 100 = 20 IU. Our reconstitution calculator does this math automatically. Just enter your vial size, water volume, and desired dose.

Ready to Calculate Your Dose?

Use our free calculator to get exact insulin units for your semaglutide concentration.

Reconstitution Plotter

Medical Disclaimer

This guide is for educational and informational purposes only. It does not constitute medical advice, professional diagnosis, or treatment recommendations. Compounded semaglutide is not FDA-approved and may vary in quality and purity. Brand-name semaglutide (Ozempic, Wegovy) is available by prescription for approved indications. Always consult with a qualified healthcare provider before using any medication. Self-administration of injectable medications carries risks including infection, incorrect dosing, and adverse reactions.