✓ Medically reviewed by · Last reviewed: May 2026
Pharmacy Researcher · 8 years experience
Pharmacy researcher with 8 years reviewing clinical drug information, generic formulation equivalence, and international pharmaceutical standards. Focuses on patient-facing accuracy in medication education.
HCG Reconstitution: BAC Water Math, Syringe Markings & Storage Protocol
Quick Answer: HCG ships as a lyophilised (freeze-dried) powder in a sealed vial. To use it, you reconstitute with bacteriostatic water (BAC water) — the amount you add determines the concentration of every subsequent dose. For a 5,000 IU vial reconstituted with 5 mL of BAC water, you get 1,000 IU/mL — meaning 25 units on a U-100 insulin syringe = 250 IU. Reconstituted hCG is stable refrigerated for 30–60 days. This guide gives the exact math for every common vial size (1,500 / 5,000 / 10,000 IU), worked examples on a U-100 syringe, and the sterile-technique protocol.
What You Need Before You Start
- Lyophilised hCG vial — HUCOG 5000IU, HUCOG 10000IU, Eutrig HP, ZyHCG HP, or Puretrig 5000IU
- Bacteriostatic water — BAC Water (0.9% benzyl alcohol), 10 mL multi-dose vial; the benzyl alcohol preserves sterility across multiple draws over 28+ days
- OR Sterile Water for Injection — Sterile Water 10 mL; suitable for single-dose use only because it lacks preservative
- U-100 insulin syringe(s) — typically 1 mL / 100 unit barrel with 29–31 g, 8–13 mm needle
- 3 or 5 mL reconstitution syringe with longer needle for transferring BAC water (the insulin syringe needle is too short and the barrel too small)
- Alcohol swabs, sharps container, gloves (optional but recommended for clinical practice)
The Core Math: Concentration After Reconstitution
The fundamental equation is:
Concentration (IU/mL) = Total IU in vial ÷ mL of BAC water added
Once you know the IU/mL, every dose is calculated as:
Dose volume (mL) = Desired dose (IU) ÷ Concentration (IU/mL)
And on a U-100 insulin syringe (where 100 units = 1 mL):
Syringe units = Dose volume (mL) × 100
That’s the entire mathematical framework. Every reconstitution decision is just plugging numbers into these three lines.
Reconstitution Tables by Vial Size
5,000 IU Vial (Most Common)
| BAC water added | Concentration | 250 IU dose | 500 IU dose | 1,000 IU dose | Vial lasts |
|---|---|---|---|---|---|
| 1 mL | 5,000 IU/mL | 5 units (0.05 mL) | 10 units (0.1 mL) | 20 units (0.2 mL) | 20 × 250 IU doses |
| 2 mL | 2,500 IU/mL | 10 units (0.1 mL) | 20 units (0.2 mL) | 40 units (0.4 mL) | 20 × 250 IU doses |
| 3 mL | 1,667 IU/mL | 15 units (0.15 mL) | 30 units (0.3 mL) | 60 units (0.6 mL) | 20 × 250 IU doses |
| 5 mL | 1,000 IU/mL | 25 units (0.25 mL) | 50 units (0.5 mL) | N/A (exceeds 1 mL syringe) | 20 × 250 IU doses |
| 10 mL | 500 IU/mL | 50 units (0.5 mL) | N/A (exceeds 1 mL syringe) | N/A | 20 × 250 IU doses |
Recommended: 3 mL reconstitution for a 5,000 IU vial. The resulting 1,667 IU/mL concentration means a 250 IU dose lands at exactly 15 units on a U-100 syringe — easy to read, easy to draw, no awkward decimals.
10,000 IU Vial
| BAC water added | Concentration | 250 IU dose | 500 IU dose | 1,000 IU dose |
|---|---|---|---|---|
| 2 mL | 5,000 IU/mL | 5 units (0.05 mL) | 10 units (0.1 mL) | 20 units (0.2 mL) |
| 5 mL | 2,000 IU/mL | 12.5 units (0.125 mL) | 25 units (0.25 mL) | 50 units (0.5 mL) |
| 10 mL | 1,000 IU/mL | 25 units (0.25 mL) | 50 units (0.5 mL) | 100 units (1 mL — full syringe) |
Recommended: 5 mL reconstitution. 500 IU dose = 25 units (clean number); 250 IU = 12.5 units (still readable on most syringes).
1,500 IU Vial (Common in PCT Kits)
| BAC water added | Concentration | 250 IU dose | 500 IU dose | 1,500 IU dose |
|---|---|---|---|---|
| 1 mL | 1,500 IU/mL | 17 units (0.17 mL) | 33 units (0.33 mL) | 100 units (1 mL) |
| 1.5 mL | 1,000 IU/mL | 25 units (0.25 mL) | 50 units (0.5 mL) | N/A (exceeds 1 mL) |
| 3 mL | 500 IU/mL | 50 units (0.5 mL) | 100 units (1 mL) | N/A |
Reading the U-100 Insulin Syringe
U-100 means “units per 100” — the syringe is calibrated so 100 units = 1 mL. Each major line is typically 5 or 10 units; each minor line is 1 or 2 units depending on syringe model.
Key conversions:
- 10 units = 0.1 mL
- 25 units = 0.25 mL
- 50 units = 0.5 mL
- 100 units = 1.0 mL (full barrel)
Practical tip: Always read the plunger position at the rubber-stopper line nearest the needle tip, not the top of the rubber. This reduces dose error by ~3–5%, which matters when you’re drawing 5–15 unit volumes.
Step-by-Step Reconstitution Protocol
- Wash hands with soap and water for 20+ seconds. Dry on clean towel.
- Lay out supplies on a clean, flat surface: hCG vial, BAC water, reconstitution syringe (3 mL), alcohol swabs, sharps container.
- Inspect the hCG vial. The lyophilised powder should be intact (no liquid, no discolouration). If the powder is partially dissolved or looks abnormal, do not use.
- Wipe the hCG vial septum with an alcohol swab. Let it air-dry 30 seconds.
- Wipe the BAC water vial septum with a fresh alcohol swab. Let air-dry.
- Draw BAC water into the 3 mL reconstitution syringe. Pull back the desired volume (e.g. 3 mL for a 5,000 IU vial). Invert the BAC water vial; the syringe should fill smoothly. Tap out any air bubbles.
- Inject BAC water into the hCG vial slowly, aiming the needle at the inside wall of the vial above the powder, not directly at the powder. Direct impact can damage the protein structure.
- Roll, don’t shake. Gently roll the vial between your palms for 30–60 seconds until the powder fully dissolves. Vigorous shaking can denature hCG and reduce potency.
- Confirm complete dissolution. The solution should be clear, colourless, with no visible particles. If anything looks off, do not use.
- Label the vial with reconstitution date and concentration in IU/mL. Use a small label or marker.
- Refrigerate immediately at 2–8 °C. Do not freeze.
Drawing a Dose for Injection
- Take the reconstituted hCG vial from the refrigerator. Let it warm to room temperature for 10–15 minutes (warm liquid injects more comfortably than cold).
- Wipe the vial septum with a fresh alcohol swab.
- Calculate the dose volume from the table above. Cross-check the math once before drawing.
- Draw the dose into a U-100 insulin syringe. Tap out air bubbles at the top of the syringe.
- Verify the volume against the calculated number of units on the syringe barrel.
- Wipe the injection site (abdomen, lateral thigh, or back of upper arm) with an alcohol swab. Let it air-dry.
- Pinch the subcutaneous tissue and insert the needle at 45–90°. Inject slowly. Remove and apply gentle pressure with the swab.
- Dispose of the syringe in a sharps container.
Storage and Stability
Lyophilised (Unreconstituted) Vials
- Store at room temperature (15–25 °C) or refrigerated (2–8 °C) per manufacturer label
- Most WHO-GMP hCG products are stable at room temperature for the 24-month shelf life when sealed
- Protect from light — keep in the original carton
- Do not freeze
Reconstituted hCG
| Diluent used | Refrigerated stability | Room temp stability |
|---|---|---|
| Bacteriostatic water (0.9% benzyl alcohol) | 30–60 days at 2–8 °C | ≤7 days (not recommended) |
| Sterile water for injection (no preservative) | Single-dose only; discard within 24 hours | Single-dose only |
Storage red flags — do not use the vial if:
- Solution is cloudy, discoloured, or contains visible particles
- Vial has been at room temperature for >48 hours
- Vial has been frozen (freeze-thaw damages glycoprotein structure)
- You used sterile (non-bacteriostatic) water and more than 24 hours has passed
- The labelled reconstitution date is more than 60 days ago
- You can’t remember when you reconstituted it (no label) — discard rather than guess
Common Reconstitution Mistakes
Mistake 1: Adding Too Much or Too Little BAC Water
Easy to do under pressure. Solution: pre-calculate concentration before starting, and write the BAC water volume on the hCG vial label before drawing.
Mistake 2: Shaking the Vial
hCG is a glycoprotein with a delicate quaternary structure. Vigorous shaking creates micro-air bubbles and shear forces that can denature the protein and reduce biological activity. Always roll, never shake.
Mistake 3: Mixing Sterile Water and Treating It Like BAC Water
Sterile water lacks the benzyl alcohol preservative. Reconstituted with sterile water, hCG is single-dose-only. Many users accidentally treat sterile-water-reconstituted vials as multi-dose for weeks — bacterial contamination risk is real.
Mistake 4: Drawing Air Without Equilibrating Pressure
Before drawing a dose, inject an equal volume of air into the vial first. This prevents negative pressure that makes drawing harder and creates micro-bubbles.
Mistake 5: Reusing Syringes Across Doses
Insulin syringes are single-use. Reusing them risks contamination of the vial and needle dulling. Use a fresh syringe every injection.
Mistake 6: Not Labelling the Vial
You’ll forget the reconstitution date. Always label with: date reconstituted, BAC water volume added, calculated concentration (IU/mL), use-by date (30–60 days out).
How Long Does One Vial Last?
Math: total IU ÷ dose IU = number of doses.
- 5,000 IU vial, 250 IU dose = 20 doses; at 2x/week = 10 weeks
- 5,000 IU vial, 500 IU dose = 10 doses; at 2x/week = 5 weeks
- 10,000 IU vial, 250 IU dose = 40 doses; at 2x/week = 20 weeks (but use within 60 days refrigerated)
- 10,000 IU vial, 500 IU dose = 20 doses; at 2x/week = 10 weeks (use within 60 days)
If your dosing schedule means a vial won’t be finished within 60 days, choose a smaller vial size for fresh reconstitution.
Frequently Asked Questions
What’s the difference between bacteriostatic water and sterile water?
Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits bacterial growth and allows multi-dose use for 28+ days. Sterile water has no preservative and is single-dose-only. For reconstituting multi-dose hCG vials, always use BAC water.
Can I reconstitute with saline?
Not recommended. The sodium chloride in saline can interact with hCG’s glycoprotein structure and reduce stability. Stick with BAC water or, for single-dose use, sterile water.
How do I dispose of an unused reconstituted vial?
Mix the remaining contents with absorbent material (used coffee grounds, cat litter) in a sealed container before discarding. Sharps go in a sharps container. Don’t pour pharmaceutical liquids down the drain.
What if I drop the reconstituted vial?
If the vial is intact and the contents look unchanged, it’s still usable. If there are visible cracks, glass particles, or contamination, discard it.
Can I freeze hCG to extend stability?
No. Freezing and thawing damages the glycoprotein structure and reduces biological activity. Stick to refrigeration at 2–8 °C.
How much BAC water do I need for multiple reconstitutions?
A 10 mL BAC water vial reconstitutes 2–3 hCG vials depending on size. The BAC water itself is good for 28 days after first puncture, so plan reconstitution timing so the BAC water is used before it expires.
Is the math any different for branded vs generic hCG?
No. WHO-GMP brands (HUCOG, Eutrig HP, ZyHCG HP, Puretrig) and originator brands (Pregnyl, Ovidrel) all use the same IU labelling. The mathematics is identical.
Why order HCG + BAC water from MedsBase
- WHO-GMP certified manufacturers — Bharat Serums, Zydus, Cadila
- Multi-dose vials — 5,000 IU and 10,000 IU sizes for cost-effective dosing
- BAC water bundled — order BAC Water (Bacteriostatic Water) alongside your hCG for ready-to-reconstitute kits
- Worldwide shipping with discreet plain-envelope packaging
- Reshipment Assurance covers any parcel not delivered in 20 business days
- Full range: HUCOG 5000IU · HUCOG 10000IU · Eutrig HP · ZyHCG HP · Puretrig 5000IU
Medical Disclaimer: Reconstitution and self-injection of hormone-replacement medications carries inherent risks including sterility loss, dose error, and injection complications. This guide is informational; always work with a qualified healthcare provider for protocol design, dose selection, and ongoing monitoring (testosterone, estradiol, haematocrit for men; ovulation tracking for women).
Written by
Sophie ChenPharmaceutical Content Researcher · 8 years experience
Sophie Chen is a pharmaceutical content researcher with 8 years covering generic medication access and clinical pharmacology. She specialises in international regulatory frameworks, bioequivalence standards, and patient-facing education on therapeutic drug classes. She is not a clinician.