Reconstituting a 5000 IU HCG Vial: BAC Water to Units Chart

How a 5000 IU HCG reconstitution chart works

HCG (human chorionic gonadotropin) ships as a freeze-dried powder. The 5000 IU number is the total activity in the vial — it does not change when you add water. What the bacteriostatic water (BAC water) sets is the concentration: how many international units (IU) end up in each millilitre, and therefore in each mark on your syringe.

A standard U-100 insulin syringe is the reference for every number on this page. On a U-100 syringe, 100 units = 1 mL, so each syringe unit is 0.01 mL. To build a 5000 IU HCG reconstitution chart you only need two steps:

1. Concentration = 5000 IU ÷ volume of BAC water added (gives IU per mL).
2. IU per syringe unit = concentration ÷ 100 (because 1 mL = 100 units).

For the maths behind syringe units in general, see HCG IU to syringe units explained and what are syringe units.

The chart: 1 ml vs 2 ml vs 3 ml of BAC water

The table below shows what 1 mL, 2 mL, and 3 mL of BAC water do to a single 5000 IU vial. The last column is the figure you actually use at the syringe: IU per unit.

Reading down the IU-per-unit column: more water means fewer IU per unit, which means you draw more syringe units for the same dose. The total dose delivered is identical — only the volume and the number of marks change. This is the same principle covered in why water amount changes syringe units.

Worked examples for a 250 IU dose

250 IU is a common HCG amount. Here is the full arithmetic at each dilution so you can see why the syringe units differ.

Same 250 IU delivered every time. The 1 mL mix gives the smallest, hardest-to-measure draw (5 units); the 3 mL mix spreads it over 15 units, which is easier to read on the barrel but uses the vial faster in volume terms.

The general formula for any dose

You are not limited to the doses in the table. For any target dose and any volume of BAC water:

Syringe units = (target IU × BAC water mL) ÷ (5000 ÷ 100), which simplifies to units = target IU × BAC water mL ÷ 50 for a 5000 IU vial.

If you would rather not do this by hand, the HCG dose calculator takes vial IU, BAC water volume, and target dose and returns the exact syringe units. Background on the mixing step is in the HCG reconstitution guide.

Choosing how much water to add

There is no single correct volume — all three give the same dose. The trade-off is measurement precision versus syringe readability:

• 1 mL — most concentrated, smallest volume, but small doses land on very few units, so a one-unit error is proportionally large.
• 2 mL — a common middle ground; 250 IU lands cleanly on 10 units and 500 IU on 20 units.
• 3 mL — most dilute, spreads doses over more units for easier reading, but the IU-per-unit figure (16.67) is not a round number.

For more on picking a dilution and the syringe size that suits it, see how much BAC water should I add and concentration explained simply. If you are weighing the 5000 IU vial against a larger one, the 5000 IU vs 10000 IU vials comparison covers that separately.

After mixing: storage and a safety note

Once reconstituted, HCG is a liquid that degrades at room temperature. Manufacturer labelling for chorionic gonadotropin products specifies that the reconstituted solution should be refrigerated and used within a limited in-use period — the FDA-approved Pregnyl label, for example, states the reconstituted solution is stable for 60 days when refrigerated and should not be frozen. Always follow the storage and discard window on your specific product's label. See HCG storage and expiry for the detail.

This page is a measurement and arithmetic reference, not a dosing recommendation. HCG is a prescription medication, and the dose, 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.

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