How to Reconstitute Peptides: Dosage Calculator, Unit Conversion Chart and Step-by-Step Guide
Complete peptide reconstitution guide — how much BAC water to add, how to convert mg to units on a U-100 syringe, worked dosage examples and a quick-draw conversion chart.
Reconstitution is where most peptide mistakes happen. Not in the injection, not in the storage — in the two minutes where someone adds water to a vial and then has to work out how many units on a syringe equals the dose they actually want.
The good news is that the entire thing reduces to one formula. Learn it once and it applies to every compound you will ever handle, from BPC-157 to retatrutide.
This guide covers the maths, the procedure, a full conversion chart, and worked examples for the most commonly used peptides.
Important: This guide is for educational purposes and is intended to support use under practitioner supervision. It does not constitute medical advice. All protocols should be overseen by a qualified healthcare practitioner.
What is reconstitution?
Peptides are supplied as a lyophilised — freeze-dried — powder in a sterile, sealed vial. Reconstitution is the process of dissolving that powder in a suitable solvent to produce an injectable solution of a known concentration.
The solvent is almost always bacteriostatic water (BAC water), which contains 0.9% benzyl alcohol as a preservative. That preservative is what allows a reconstituted vial to remain stable for up to 30 days at 2–8 °C.
Sterile water for injection (SWFI) contains no preservative. A vial reconstituted with sterile water should be used within 24 hours. For any multi-dose vial, BAC water is the correct choice.
Equipment you need
| Item | Notes |
|---|---|
| Bacteriostatic water | 0.9% benzyl alcohol; the preferred solvent for multi-use vials |
| Insulin syringe (U-100) | 1 mL, 29–31 gauge; standard for subcutaneous injection |
| Larger draw syringe | Optional; 3–5 mL for drawing BAC water into the peptide vial |
| Alcohol swabs (70% IPA) | Wipe vial tops before every single needle insertion |
| Refrigerator (2–8 °C) | For storage after reconstitution; never freeze reconstituted solution |
| Sharps container | Biohazard sharps bin — never recap needles |
The master formula
Everything in peptide dosing comes down to this:
Concentration (mg/mL) = Peptide mass (mg) ÷ BAC water added (mL)
From that, two derived forms cover every calculation you'll do:
Volume to inject (mL) = Desired dose (mg) ÷ Concentration (mg/mL)
Units on a U-100 syringe = Volume to inject (mL) × 100
Understanding the U-100 syringe
A U-100 insulin syringe holds 1 mL in total. The barrel is graduated into 100 equal units, so each unit equals 0.01 mL. This is the universal reference point for peptide dosing, and once it clicks, the conversions stop being confusing.
| Syringe mark | Volume | Fraction of 1 mL |
|---|---|---|
| 10 units | 0.10 mL | One tenth |
| 20 units | 0.20 mL | One fifth |
| 25 units | 0.25 mL | One quarter |
| 50 units | 0.50 mL | One half |
| 100 units | 1.00 mL | Full syringe |
Concentration reference chart
This table shows the resulting concentration for common vial sizes and BAC water volumes. Choose your water volume based on your target dose and how comfortable the resulting number is to draw.
| Vial size | BAC water added | Concentration | Per unit on U-100 |
|---|---|---|---|
| 1 mg | 1.0 mL | 1.0 mg/mL | 10 mcg |
| 1 mg | 2.0 mL | 0.5 mg/mL | 5 mcg |
| 2 mg | 1.0 mL | 2.0 mg/mL | 20 mcg |
| 2 mg | 2.0 mL | 1.0 mg/mL | 10 mcg |
| 5 mg | 1.0 mL | 5.0 mg/mL | 50 mcg |
| 5 mg | 2.0 mL | 2.5 mg/mL | 25 mcg |
| 5 mg | 5.0 mL | 1.0 mg/mL | 10 mcg |
| 10 mg | 1.0 mL | 10.0 mg/mL | 100 mcg |
| 10 mg | 2.0 mL | 5.0 mg/mL | 50 mcg |
| 10 mg | 5.0 mL | 2.0 mg/mL | 20 mcg |
| 10 mg | 10.0 mL | 1.0 mg/mL | 10 mcg |
Practical tip: if a dose works out to an awkward number like 12.5 units, add more BAC water to lower the concentration. Drawing 25 units is far easier to do accurately than finding the halfway point between the 12 and 13 marks.
Quick-draw conversion chart
Find your concentration across the top and your desired dose down the side to read off the units to draw.
| Dose ↓ / Conc → | 0.5 mg/mL | 1.0 mg/mL | 2.0 mg/mL | 2.5 mg/mL | 5.0 mg/mL | 10.0 mg/mL |
|---|---|---|---|---|---|---|
| 50 mcg | 10 U | 5 U | 2.5 U | 2 U | 1 U | 0.5 U |
| 100 mcg | 20 U | 10 U | 5 U | 4 U | 2 U | 1 U |
| 200 mcg | 40 U | 20 U | 10 U | 8 U | 4 U | 2 U |
| 250 mcg | 50 U | 25 U | 12.5 U | 10 U | 5 U | 2.5 U |
| 500 mcg | 100 U | 50 U | 25 U | 20 U | 10 U | 5 U |
| 1 mg | — | 100 U | 50 U | 40 U | 20 U | 10 U |
| 2 mg | — | — | 100 U | 80 U | 40 U | 20 U |
| 5 mg | — | — | — | — | 100 U | 50 U |
A dash means the volume exceeds a 1 mL syringe. Increase your BAC water volume to lower the concentration.
Step-by-step reconstitution procedure
1. Wash your hands thoroughly and work on a clean, flat surface.
2. Remove both vials from refrigeration and allow the peptide vial and the BAC water to reach room temperature — around 5–10 minutes. This reduces the risk of thermal shock to the peptide.
3. Swab the rubber septum of both vials with a fresh 70% IPA swab. Allow 10 seconds to air-dry before inserting any needle.
4. Draw your required volume of BAC water into the syringe. For example, 1 mL for a 1 mg/mL concentration from a 1 mg vial, or 2 mL for a 5 mg/mL concentration from a 10 mg vial.
5. Insert the needle into the peptide vial at an angle so that the stream of water runs down the inside wall of the vial rather than landing directly on the powder cake. This prevents foaming and protects the peptide from degradation.
6. Do not shake. Gently roll the vial between your palms or swirl it slowly until the powder is fully dissolved. Most peptides dissolve within 30–60 seconds; some, notably TB-500, take one to two minutes.
7. Inspect the solution visually. It should be clear and colourless, or very faintly yellow for some compounds. Discard if cloudy, particulate or discoloured.
8. Label the vial immediately with the compound name, concentration in mg/mL, the date reconstituted, and your initials. Store at 2–8 °C.
Never use ultrasonic baths, vortex mixers, or vigorous shaking. Peptide bonds are fragile and mechanical stress degrades potency. Gentle swirling only.
Worked dosage examples
Example A — BPC-157, 250 mcg dose
Vial: 5 mg. BAC water added: 2.0 mL.
- Concentration = 5 mg ÷ 2.0 mL = 2.5 mg/mL
- Desired dose = 250 mcg = 0.25 mg
- Volume = 0.25 mg ÷ 2.5 mg/mL = 0.10 mL
- Units = 0.10 × 100 = 10 units
Draw to 10 units. This delivers exactly 250 mcg.
Example B — BPC-157, 500 mcg dose (same vial)
Vial: 5 mg. BAC water added: 2.0 mL → concentration 2.5 mg/mL.
- Desired dose = 500 mcg = 0.50 mg
- Volume = 0.50 ÷ 2.5 = 0.20 mL
- Units = 20 units
Draw to 20 units.
Example C — GHK-Cu, 1 mg dose
Vial: 5 mg. BAC water added: 5.0 mL.
- Concentration = 5 ÷ 5.0 = 1.0 mg/mL
- Desired dose = 1 mg
- Volume = 1 ÷ 1.0 = 1.0 mL
- Units = 100 units — a full syringe
A full 1 mL syringe delivers 1 mg GHK-Cu, a typical subcutaneous dose.
Example D — Ipamorelin, 200 mcg dose
Vial: 2 mg. BAC water added: 2.0 mL.
- Concentration = 2 ÷ 2.0 = 1.0 mg/mL
- Desired dose = 200 mcg = 0.20 mg
- Volume = 0.20 ÷ 1.0 = 0.20 mL
- Units = 20 units
Example E — Semaglutide, 0.25 mg starting dose
Vial: 2 mg. BAC water added: 1.0 mL.
- Concentration = 2 ÷ 1.0 = 2.0 mg/mL
- Desired dose = 0.25 mg
- Volume = 0.25 ÷ 2.0 = 0.125 mL
- Units = 12.5 units — awkward, sitting between the 12 and 13 marks
Better approach: reconstitute in 2 mL instead, giving 1 mg/mL, and draw 25 units. Same dose, far easier to measure accurately. This is exactly the situation where adding more water solves the problem.
Example F — TB-500, 2.5 mg dose
Vial: 5 mg. BAC water added: 1.0 mL.
- Concentration = 5 ÷ 1.0 = 5.0 mg/mL
- Desired dose = 2.5 mg
- Volume = 2.5 ÷ 5.0 = 0.50 mL
- Units = 50 units
Note that TB-500 needs a longer dissolution time — one to two minutes of gentle swirling.
Compound-specific reconstitution notes
| Compound | Vial | BAC water | Concentration | Notes |
|---|---|---|---|---|
| BPC-157 | 5 mg | 2 mL | 2.5 mg/mL | Dissolves readily, clear solution. Light-sensitive — store in an amber vial or wrap in foil. |
| TB-500 | 5 mg | 1–2 mL | 2.5–5 mg/mL | Slow to dissolve; allow 2–3 minutes of gentle swirling. May look slightly viscous initially. |
| GHK-Cu | 5 mg | 5 mL | 1 mg/mL | A blue-green tint is normal — it's a copper chelate. Avoid contact with vitamin C or citric acid, which causes copper displacement. |
| CJC-1295 No-DAC | 2 mg | 2 mL | 1 mg/mL | Stable in BAC water, use within 28 days. Compatible with ipamorelin in the same syringe. |
| Ipamorelin | 2 mg | 2 mL | 1 mg/mL | Clear solution. Can be combined with CJC-1295 No-DAC in the same syringe. |
| Semaglutide | 2 mg | 1–2 mL | 1–2 mg/mL | 2 mL gives 1 mg/mL, where 25 units = 0.25 mg. Weekly subcutaneous injection. |
| Tirzepatide | 5 mg | 1–2 mL | 2.5–5 mg/mL | Dissolves readily. A 2.5 mg starting dose is 50 units at 5 mg/mL. |
| Retatrutide | 5 mg | 2 mL | 2.5 mg/mL | Handle as for tirzepatide. Long-term stability data is limited — use within 21 days. |
| KPV | 50 mg | 10 mL | 5 mg/mL | Very water-soluble and extremely stable once reconstituted. |
Storage and stability after reconstitution
| State | Storage temperature | Shelf life | Notes |
|---|---|---|---|
| Lyophilised powder, sealed | Room temperature (15–25 °C) | To expiry date, typically 24+ months | Keep away from direct light and moisture |
| Lyophilised powder, unsealed | 2–8 °C refrigerated | Within 6 months | Do not freeze |
| Reconstituted in BAC water | 2–8 °C refrigerated | 28–30 days | Do not freeze; discard if cloudy |
| Reconstituted in sterile water | 2–8 °C refrigerated | Within 24 hours | Prepare only what you need immediately |
| Reconstituted, frozen in aliquots | −20 °C | Up to 3 months | Single freeze only; never refreeze after thawing |
Never boil, autoclave, or expose reconstituted peptide solutions to temperatures above 37 °C. Heat permanently denatures peptide structure and cannot be undone.
Store reconstituted vials at the back of the fridge, not in the door. The door experiences a temperature spike every time the fridge is opened, and for GLP-1 class peptides in particular, that cycling meaningfully shortens usable life.
Subcutaneous injection technique
Most peptides are administered subcutaneously — into the fat layer just beneath the skin. Common sites are the abdomen (2–3 cm from the navel), outer thigh, or lower back.
- Swab the injection site with an IPA swab and allow 10 seconds to dry.
- Pinch a fold of skin between thumb and forefinger, roughly 1–2 cm.
- Insert a 29–31 gauge needle at a 45° angle, or 90° if you're pinching a generous fold.
- Inject slowly, over 5–10 seconds. Rapid injection increases local discomfort.
- Withdraw at the same angle and apply light pressure with a dry swab. Do not rub.
- Dispose of the needle in a sharps container immediately. Never recap.
Rotation protocol: picture a clock face around the navel and advance one position with each injection, keeping a minimum of 3–4 cm from the previous site. This prevents skin thickening and keeps absorption consistent.
Troubleshooting
| Issue | What to do |
|---|---|
| Powder won't dissolve | Allow more time and gently swirl or roll the vial. Some peptides, particularly TB-500, need 2–3 minutes. Never shake. |
| Cloudy solution | Do not use. May indicate contamination, precipitation, or degraded peptide. Discard. |
| Floating particles | Discard. Could be peptide aggregates or particulate contamination — neither can be filtered out. |
| Blue or green tint | Normal for GHK-Cu due to the copper content. Other peptides should be clear to faintly yellow. |
| Pain at injection site | Check your needle gauge (use 30–31 G), slow the injection speed, and make sure the IPA is fully dry before injecting. |
| Foamy solution | Caused by injecting BAC water directly onto the powder. Discard if severely foamed; otherwise wait about 10 minutes for bubbles to settle. |
| Unsure of concentration | Discard and reconstitute fresh. Never estimate — always recalculate from the formula. |
| Air bubble in syringe | Tap the barrel gently and expel the bubble upward before injecting. Small bubbles in a subcutaneous injection are not dangerous but are best removed. |
Frequently asked questions
How much BAC water should I add to my peptide vial?
There is no single correct answer — it depends on the dose you want and how easy that dose is to draw. Work backwards: pick a concentration where your typical dose lands on a round number of units. For a 5 mg vial with a 250 mcg dose, 2 mL gives you a clean 10 units. Adding more water is never wrong from a stability standpoint; it simply means drawing a larger volume.
Can I use sterile water instead of bacteriostatic water?
Only if you're using the entire vial within 24 hours. Sterile water has no preservative, so any multi-dose vial reconstituted with it becomes a contamination risk. For anything you'll draw from more than once, use BAC water.
What happens if I shake the vial?
Shaking triggers fibrillar aggregation — the peptide chains clump together and the compound loses activity. This is irreversible. Once a peptide has aggregated, no amount of mixing, warming or filtering will restore it. Gentle swirling only.
How long does a reconstituted peptide last?
Generally 28–30 days refrigerated in BAC water, though this varies by compound. GLP-1 class peptides such as tirzepatide and semaglutide sit at the shorter end of that window, and retatrutide should be used within 21 days given limited stability data. More robust compounds like BPC-157 and TB-500 tolerate longer. Label every vial with its reconstitution date so you're never guessing.
Can I freeze a reconstituted vial?
Not in a normal fridge-freezer for routine use. Ice crystal formation disrupts peptide structure. Pre-aliquoted solution stored at −20 °C can hold for up to three months, but only as a single freeze — never refreeze after thawing.
How do I convert mg to units on an insulin syringe?
Divide your desired dose in mg by the concentration in mg/mL to get the volume in mL, then multiply by 100. A 0.5 mg dose from a 2.5 mg/mL vial is 0.2 mL, which is 20 units. The quick-draw chart above covers the most common combinations.
My vial has gone cloudy before the expiry window. What now?
Discard it and do not inject. Then consider the cause: cloudiness well inside the shelf life, with correct storage, may indicate a product quality issue rather than user error. If you bought from Striata, get in touch — describe what you're seeing and when you reconstituted it, and we'll work out what happened.
Questions about a specific compound?
If you're unsure about a reconstitution volume, a dose calculation, or whether a vial is still good to use, message us. We'd rather answer a question than have someone guess.
Website: striatalabs.co.za
Email: info@striatalabs.co.za
WhatsApp: +27 78 213 7905
This guide is produced by Striata Research Peptides for educational purposes. It does not constitute medical advice. All products supplied by Striata Labs are research-grade compounds intended for use under qualified practitioner supervision, in compliance with SAHPRA guidelines and applicable regulations. Striata Labs accepts no liability for misuse arising from inadequate practitioner supervision.
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