How Much BAC Water to Add to Peptides — Reconstitution Guide & Reference Charts
Overview
The amount of bacteriostatic water you add to a lyophilized peptide determines the concentration of the resulting solution — and concentration directly affects the precision and reproducibility of your research. Add too little solvent and you get a highly concentrated solution that is difficult to measure accurately. Add too much and the solution becomes too dilute for practical use.
This guide explains how reconstitution volume works, provides reference charts for the most common peptide quantities, and walks through the math so you can calculate the right volume for any peptide at any target concentration. If you prefer to skip the math, use our Peptide Reconstitution Calculator.
How Reconstitution Volume Affects Concentration
The relationship is straightforward:
Concentration (mcg per unit) = Total peptide amount ÷ Total solvent volume
For example, if you reconstitute a 5 mg peptide vial with 2 mL of BAC water:
- 5 mg = 5,000 mcg
- 5,000 mcg ÷ 2 mL = 2,500 mcg per mL
- Since 1 mL = 100 units on a standard U-100 syringe: 25 mcg per unit marking
The same 5 mg peptide reconstituted with 1 mL would yield 5,000 mcg/mL (50 mcg per unit) — twice as concentrated. With 5 mL, it would be 1,000 mcg/mL (10 mcg per unit) — much more dilute but easier to measure small quantities precisely.
There is no single "correct" volume. The right amount depends on the concentration your research protocol requires and the precision of your measuring instruments.
Quick Reference: Common Reconstitution Volumes
The following tables show the resulting concentration for the most common peptide sizes available from Heritage Labs USA. All values assume reconstitution with bacteriostatic water.
5 mg Peptide Vial
Applies to: BPC-157, TB-500, Ipamorelin, TZ2 5mg, SM1 5mg, RT3 5mg, Sermorelin, Tesamorelin, Selank, Semax, DSIP, and other 5 mg peptides.
| BAC Water Added | Concentration (mcg/mL) | Per Unit on U-100 Syringe |
|---|---|---|
| 1 mL | 5,000 mcg/mL | 50 mcg |
| 2 mL (common) | 2,500 mcg/mL | 25 mcg |
| 2.5 mL | 2,000 mcg/mL | 20 mcg |
| 5 mL | 1,000 mcg/mL | 10 mcg |
10 mg Peptide Vial
Applies to: CJC-1295, MOTS-C, PT-141, Epithalon, TZ2 10mg, RT3 10mg, and other 10 mg peptides.
| BAC Water Added | Concentration (mcg/mL) | Per Unit on U-100 Syringe |
|---|---|---|
| 1 mL | 10,000 mcg/mL | 100 mcg |
| 2 mL | 5,000 mcg/mL | 50 mcg |
| 3 mL (common) | 3,333 mcg/mL | 33.3 mcg |
| 5 mL | 2,000 mcg/mL | 20 mcg |
30 mg Peptide Vial
Applies to: TZ2 30mg, RT3 30mg, and other higher-quantity vials.
| BAC Water Added | Concentration (mcg/mL) | Per Unit on U-100 Syringe |
|---|---|---|
| 2 mL | 15,000 mcg/mL | 150 mcg |
| 3 mL (common) | 10,000 mcg/mL | 100 mcg |
| 5 mL | 6,000 mcg/mL | 60 mcg |
| 6 mL | 5,000 mcg/mL | 50 mcg |
60 mg Peptide Vial
Applies to: TZ2 60mg and other high-quantity vials.
| BAC Water Added | Concentration (mcg/mL) | Per Unit on U-100 Syringe |
|---|---|---|
| 3 mL | 20,000 mcg/mL | 200 mcg |
| 6 mL (common) | 10,000 mcg/mL | 100 mcg |
| 10 mL | 6,000 mcg/mL | 60 mcg |
How to Calculate Any Reconstitution Volume
If your peptide quantity or target concentration is not in the tables above, the formula is simple:
BAC water to add (mL) = Peptide amount (mcg) ÷ Desired concentration (mcg/mL)
Example: You have a 10 mg vial and want a concentration of 2,000 mcg/mL.
- 10 mg = 10,000 mcg
- 10,000 mcg ÷ 2,000 mcg/mL = 5 mL of BAC water
Example: You have a 5 mg vial and want 250 mcg per 10 units on a U-100 syringe.
- 250 mcg per 10 units = 2,500 mcg per 100 units = 2,500 mcg/mL
- 5,000 mcg ÷ 2,500 mcg/mL = 2 mL of BAC water
For any calculation, our Peptide Reconstitution Calculator handles the math automatically — enter your peptide amount and desired concentration and it tells you exactly how much solvent to add.
Reconstitution Procedure
Once you have determined the correct volume of BAC water, the reconstitution process is straightforward:
- Prepare the BAC water vial. Wipe the rubber septum of the BAC water vial with an alcohol swab. Allow to air dry.
- Draw the calculated volume. Using a sterile syringe, draw the exact amount of BAC water you calculated from the tables or formula above.
- Add to the peptide vial. Insert the needle through the peptide vial's rubber septum. Direct the stream of water against the inside wall of the vial — not directly onto the lyophilized powder. Spraying directly onto the cake can cause foaming and may damage sensitive peptide bonds.
- Allow it to dissolve. Most peptides dissolve within 1–3 minutes. Do not shake or vortex aggressively. If the peptide has not fully dissolved after 3 minutes, gently roll the vial between your palms or set it in the refrigerator for 15–30 minutes and check again.
- Verify clarity. A properly reconstituted peptide solution should be clear and colorless. Cloudiness, visible particles, or a milky appearance may indicate an issue — see our guide on when to use acetic acid water instead.
- Store immediately. Refrigerate at 2–8°C. Use within 28 days. For detailed storage guidance, see our Peptide Storage Guide.
BAC Water vs. Other Solvents
Bacteriostatic water is the default reconstitution solvent for the vast majority of research peptides. However, some peptides require acetic acid water due to pH-dependent solubility. If you reconstitute a peptide with BAC water and it remains cloudy or fails to dissolve, the peptide likely requires an acidic solvent.
For a complete breakdown of which peptides require which solvent, read our guide: Acetic Acid Water vs. Bacteriostatic Water: Which Solvent for Peptide Research.
| Solvent | Use When | Shelf Life After Reconstitution |
|---|---|---|
| Bacteriostatic water | Default for most peptides | 21–30 days at 2–8°C |
| Acetic acid water (0.6%) | Peptides that won't dissolve in neutral pH (GHK-Cu, AOD-9604, IGF-1 LR3) | 21–30 days at 2–8°C |
| Sterile water (no preservative) | Single-use research only | 24–48 hours at 2–8°C |
Common Reconstitution Mistakes
| Mistake | Why It's a Problem | What to Do Instead |
|---|---|---|
| Spraying BAC water directly onto the powder | Causes foaming, can damage peptide bonds | Direct the stream against the vial wall and let it run down |
| Shaking the vial vigorously | Creates air bubbles, can denature the peptide | Gently swirl or roll between palms |
| Using too little solvent | Creates a highly concentrated solution that is hard to measure accurately with standard syringes | Use enough solvent that each unit marking represents a practical amount |
| Using too much solvent | Creates an overly dilute solution — large volumes needed for small quantities of peptide | Match solvent volume to your research protocol requirements |
| Using the wrong solvent | Some peptides require acidic conditions — BAC water will not dissolve them | Check the solvent guide before reconstituting |
| Using tap water or saline | Non-sterile water introduces contaminants; saline can interfere with peptide stability | Always use pharmaceutical-grade BAC water |
Frequently Asked Questions
Can I add more BAC water after initial reconstitution?
Yes. If you reconstituted with too little solvent and the concentration is too high for practical measurement, you can add more BAC water to dilute further. Just recalculate the new concentration based on the total volume added. The peptide will not be harmed by the addition of more solvent.
Does the BAC water volume affect the peptide's stability?
Slightly. More dilute solutions have a marginally higher surface-area-to-volume ratio, which can accelerate oxidation in some peptides. In practice, this difference is negligible within the normal 28-day use window. Use whatever volume your research protocol requires and store properly.[1]
What if my peptide doesn't fully dissolve?
First, give it more time — refrigerate the vial for 15–30 minutes and check again. Some peptides dissolve slowly. If it remains cloudy or particulate after 30 minutes, the peptide likely requires acetic acid water instead of BAC water. See our solvent comparison guide for a complete list of which peptides need which solvent.
How much BAC water do I need on hand?
A 10 mL BAC water vial is enough to reconstitute 3–5 peptide vials at typical volumes (2–3 mL each). For researchers working with multiple peptides simultaneously, keeping 2–3 BAC water vials in stock ensures you are never waiting on supplies. Heritage Labs also carries 3 mL vials for smaller-scale use.
Tools and Related Guides
- Peptide Reconstitution Calculator — enter your peptide amount and desired concentration, get the exact BAC water volume instantly
- Acetic Acid Water vs. BAC Water — which solvent for which peptide
- Peptide Storage Guide — temperature, shelf life, and degradation signs
References
- Manning, M.C., et al. "Stability of Protein Pharmaceuticals: An Update." Pharmaceutical Research, vol. 27, 2010, pp. 544–575.
- United States Pharmacopeia (USP). "Bacteriostatic Water for Injection." USP-NF General Chapter.
- Chi, E.Y., et al. "Physical Stability of Proteins in Aqueous Solution: Mechanism and Driving Forces." Pharmaceutical Research, vol. 20, no. 9, 2003, pp. 1325–1336.