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HCG · Reconstitution math

Last updated: June 2026 · Reviewed June 2026 · Built by the InjectBuddy team

How do you reconstitute a 5000 IU HCG vial? BAC water to units chart

To reconstitute a 5000 IU HCG vial, inject bacteriostatic water into the vial — 1, 2, 3 or 5 mL are the common volumes — giving 50 IU per syringe unit with 1 mL, 25 IU with 2 mL, about 16.7 IU with 3 mL, and 10 IU with 5 mL on a U-100 insulin syringe. The bacteriostatic water never changes the 5000 IU total; it only sets the concentration, so a fixed dose lands on a different number of syringe units at each dilution. This guide explains the maths behind the chart, walks through eight worked examples, and answers the questions people ask most about reconstituting HCG.

Key takeaways

  • The vial holds 5000 IU regardless of water added; water sets concentration, not dose.
  • IU per unit = 5000 ÷ (BAC water mL × 100). So 1 mL → 50, 2 mL → 25, 3 mL → 16.67, 5 mL → 10 IU per unit.
  • Units for any dose = target IU × BAC water mL ÷ 50.
  • Skip the arithmetic with the HCG dose calculator — enter vial IU, water volume and target IU.

What the chart actually fixes

HCG (human chorionic gonadotropin) ships as a freeze-dried powder, and the FDA-approved labels express its strength in USP units — 5000 or 10,000 units per vial. That number is the total activity sealed in the vial, and reconstitution does not add or remove any of it. What the bacteriostatic water (BAC water) sets is the concentration: how many IU end up in each milliliter, and therefore in each mark on your syringe.

Every figure on this page assumes a U-100 insulin syringe, where 100 units = 1 mL, so one syringe unit is 0.01 mL. That single fact is what links IU to units. If you draw with a different syringe scale, the unit numbers below will not match — the underlying volume still will. For the per-unit conversion in isolation, see HCG IU to syringe units explained.

How this is calculated

Building a 5000 IU HCG reconstitution chart needs only two divisions, in order:

  1. Concentration = 5000 IU ÷ BAC water (mL) → IU per mL.
  2. IU per syringe unit = concentration ÷ 100, because 1 mL holds 100 U-100 units.

Those two steps collapse into one shortcut. Since 5000 ÷ 100 = 50, the units you draw for any dose are simply:

Syringe units = target IU × BAC water (mL) ÷ 50.

The "50" is specific to a 5000 IU vial. A 10,000 IU vial uses 100 in place of 50, which is why its IU-per-unit figures are exactly double at the same water volume — the basis of the 5000 IU vs 10,000 IU vials comparison.

The chart: 1, 2, 3 and 5 mL of BAC water

The table covers the four volumes people actually draw into a 5000 IU vial. The IU-per-unit column is the number you work from at the syringe; the last two columns convert two common doses straight to units.

BAC water addedConcentration (IU/mL)IU per unit (U-100)Units for 250 IUUnits for 500 IUUnits for 1000 IU
1 mL5000 IU/mL50 IU5 units10 units20 units
2 mL2500 IU/mL25 IU10 units20 units40 units
3 mL1666.7 IU/mL16.67 IU15 units30 units60 units
5 mL1000 IU/mL10 IU25 units50 units100 units

Reading down the IU-per-unit column: more water means fewer IU per unit, so the same dose lands on more syringe units and a larger volume. The total IU delivered never changes — only the readability and the volume do, the principle behind why water amount changes syringe units.

5000 IU HCG reconstitution: IU per syringe unit by BAC water volume Four horizontal bars showing that a 5000 IU vial gives 50 IU per unit at 1 mL, 25 at 2 mL, 16.7 at 3 mL and 10 at 5 mL of bacteriostatic water. 5000 IU vial — IU per U-100 unit 1 mL 50 IU 2 mL 25 IU 3 mL 16.67 IU 5 mL 10 IU More water → fewer IU per unit → more units drawn for the same dose
Bar length is IU per U-100 unit. Adding water shrinks the IU each mark carries, never the 5000 IU total.

Worked examples

Each block below is the full arithmetic for one combination, so you can audit the chart rather than trust it.

250 IU at 1 mL

Concentration = 5000 ÷ 1 = 5000 IU/mL. IU per unit = 5000 ÷ 100 = 50. Units = 250 ÷ 50 = 5 units (0.05 mL).

250 IU at 2 mL

Concentration = 5000 ÷ 2 = 2500 IU/mL. IU per unit = 2500 ÷ 100 = 25. Units = 250 ÷ 25 = 10 units (0.10 mL).

250 IU at 3 mL

Concentration = 5000 ÷ 3 = 1666.7 IU/mL. IU per unit = 1666.7 ÷ 100 = 16.67. Units = 250 ÷ 16.67 = 15 units (0.15 mL).

500 IU at 2 mL

At 2 mL each unit is 25 IU. Units = 500 ÷ 25 = 20 units (0.20 mL). Or by the shortcut: 500 × 2 ÷ 50 = 20.

500 IU at 5 mL

Concentration = 5000 ÷ 5 = 1000 IU/mL → 10 IU per unit. Units = 500 ÷ 10 = 50 units (0.50 mL) — half a U-100 syringe for one dose.

350 IU at 2 mL (off-chart dose)

Shortcut: 350 × 2 ÷ 50 = 14 units (0.14 mL). Check: at 25 IU/unit, 350 ÷ 25 = 14. The two methods agree.

1000 IU at 1 mL

At 1 mL each unit is 50 IU. Units = 1000 ÷ 50 = 20 units (0.20 mL). The same 1000 IU at 3 mL needs 60 units — same dose, triple the marks.

Doses left in the vial

A 5000 IU vial reconstituted for 250 IU doses yields 5000 ÷ 250 = 20 doses. At 500 IU doses it is 5000 ÷ 500 = 10 doses, independent of the water volume.

Choosing how much water to add

No volume is "correct" — all four deliver the identical dose. The trade-off is measurement precision versus syringe readability:

  • 1 mL — most concentrated; small doses land on very few units, so a one-unit slip is proportionally large.
  • 2 mL — a common middle ground; 250 IU lands cleanly on 10 units, 500 IU on 20.
  • 3 mL — more dilute and easier to read, but 16.67 IU per unit is not a round number.
  • 5 mL — most dilute; doses spread across many easy-to-read units but a 500 IU draw fills half the barrel.

For picking a dilution and matching syringe, see how much BAC water should I add and concentration explained simply. The mixing step itself is covered in the HCG reconstitution guide, and a typical fertility-clinic regimen in the 500 IU twice-weekly draw.

After mixing: storage and safety

Reconstituted HCG is a liquid that degrades at room temperature. The FDA-approved Pregnyl label states the reconstituted solution is stable for 60 days when refrigerated and must not be frozen; the bacteriostatic water that preserves it contains benzyl alcohol and is "not for use in neonates." Always follow the storage and discard window on your specific product's label — see HCG storage and expiry.

This page is a measurement and arithmetic reference, not a dosing recommendation. HCG is a prescription medication; the dose, the dilution, and whether it is appropriate at all are clinical decisions for a prescriber. Use the chart to convert a dose your clinician has set into syringe units — not to choose the dose itself.

So, how do you reconstitute a 5000 IU HCG vial?

Draw bacteriostatic water into a syringe and inject it slowly down the side of the HCG vial — 2 mL is the most common choice, giving a clean 25 IU per syringe unit. The total is always 5000 IU; the water volume only sets the concentration, which determines how many marks you draw for a given dose, using the formula: syringe units = target IU × BAC water (mL) ÷ 50. Enter your actual vial and dose into the HCG dose calculator to get your exact units instantly.

FAQs

How do you reconstitute a 5000 IU HCG vial?
Draw bacteriostatic water into a syringe and inject it slowly into the HCG vial. Common volumes are 1, 2, 3 or 5 mL — the total stays 5000 IU, but more water means fewer IU per syringe unit, so a fixed dose lands on more unit marks.
How many units is 250 IU of HCG from a 5000 IU vial?
On a U-100 syringe it depends on the water added: 1 mL gives 5 units, 2 mL gives 10 units, 3 mL gives 15 units and 5 mL gives 25 units — all delivering the same 250 IU.
Does adding more BAC water reduce the HCG dose?
No. The vial holds a fixed 5000 IU regardless of how much water you add. More water lowers the concentration, so the same dose spreads over more syringe units and a larger volume, but the total IU delivered is unchanged.
Why is the 3 mL row not a round number?
5000 ÷ 3 = 1666.7 IU/mL, or 16.67 IU per unit, which does not divide evenly. That is fine arithmetically, but it is why many people choose 1, 2 or 5 mL, where the IU-per-unit figures (50, 25, 10) are round.
Which syringe does this chart assume?
A U-100 insulin syringe, where 100 units equal 1 mL and each unit is 0.01 mL. On a different syringe scale the unit numbers change, though the underlying volume stays the same.

Related guides

Sources

  • U.S. Food & Drug Administration / DailyMed. Pregnyl (chorionic gonadotropin) for injection — prescribing information: 10,000 USP units per vial, reconstitution, and 60-day refrigerated in-use stability. National Library of Medicine. dailymed.nlm.nih.gov.
  • DailyMed. Chorionic Gonadotropin for injection kit (10,000 USP units, lyophilized powder with bacteriostatic water diluent) — FDA label, Fresenius Kabi USA. National Library of Medicine. dailymed.nlm.nih.gov.
  • DailyMed. Bacteriostatic Water for Injection, USP — label: benzyl-alcohol-preserved diluent for reconstitution; not for use in neonates. National Library of Medicine. dailymed.nlm.nih.gov.
  • Madhusoodanan V, Patel P, Lima TFN, et al. Human Chorionic Gonadotropin monotherapy for the treatment of hypogonadal symptoms in men with total testosterone > 300 ng/dL. Int Braz J Urol. 2019;45(5):1008-1012. pmc.ncbi.nlm.nih.gov/articles/PMC6844348.

This guide is for general educational purposes only and does not constitute medical advice. Always follow your prescriber's specific instructions.

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