How much solvent do I add to an HCG vial?

The Pregnyl label is unusually explicit about this: “Remove 1 to 10 mL of solvent and add to vial with lyophilized powder.” A ten-fold range, all of it on-label, because the solvent sets concentration rather than dose. In a 10,000 unit vial, 1 mL gives 10,000 units/mL and 10 mL gives 1,000 units/mL — the same dose, ten times the volume to draw. Pregnyl supplies its own solvent (water for injection with 0.56% sodium chloride and 0.9% benzyl alcohol as preservative); Novarel and the Fresenius Kabi generic use bacteriostatic water. Also note the labels say intramuscular use only.

How many units per mL after reconstituting 10,000 IU of HCG?

Divide the units by the millilitres, exactly as you would with milligrams. 10,000 units in 10 mL is 1,000 units/mL; in 5 mL it is 2,000 units/mL; in 1 mL it is 10,000 units/mL. The Pregnyl label explicitly allows anywhere from 1 to 10 mL of solvent. Note that USP units here are a potency measure specific to the substance — they are not interchangeable with milligrams and not the same thing as the volume units printed on a syringe barrel.

How much bacteriostatic water to reconstitute 5,000 IU of HCG?

Anywhere the label allows — the Pregnyl label permits 1 to 10 mL of solvent. The water only sets the concentration: 5,000 units in 1 mL is 5,000 units/mL, in 2 mL it is 2,500 units/mL, and in 5 mL it is 1,000 units/mL. At 1,000 units/mL a 500 unit dose is 0.5 mL, the 50 mark on a U-100 syringe; at 5,000 units/mL the same dose is 0.1 mL, the 10 mark. More water means a larger, easier-to-read draw for the same dose.

How long does reconstituted HCG last?

It depends which brand you have, which is unusual and worth checking. Pregnyl and the Fresenius Kabi generic state 60 days refrigerated at 2–8°C. Novarel states 30 days refrigerated. Same molecule, different labels, different answers.

HCG Reconstitution Calculator — 5,000 and 10,000 IU Vials

Chorionic gonadotropin, dosed in USP units rather than milligrams. Approved, reconstituted, and with a discard window that differs by brand.

Written by Kashif Khan, who builds and maintains this site and is not a clinician. Every figure links to its primary source.

Approved

FDA-approved (intramuscular use only)

Marketed as Pregnyl, Novarel and a Fresenius Kabi generic. All are lyophilised powder reconstituted before use, and all US labels specify intramuscular administration. Pregnyl supplies its own solvent containing 0.9% benzyl alcohol; Novarel and the generic use bacteriostatic water. The labels also carry, in capitals, the statement that HCG has not been demonstrated to be effective adjunctive therapy in the treatment of obesity and that there is no substantial evidence it increases weight loss beyond that from caloric restriction.

Calculator inputs

Set up your vial

Enter the label, dilution and dose. The result updates as you type.

Syringe volume

HCG in the vial

Vials are 5,000 or 10,000 USP units

Bacteriostatic water to add

Dose per injection

More optionsReverse calculation, schedule and cost

Enter the bacteriostatic water you added and get the volume to draw.

Injections per week

Discard afterdays

Vial priceoptional

Draw to

50units(0.5 mL)

Concentration: 1000 iu/mL
Water added: 10 mL
Doses in vial: 20

How the concentration is calculated

This divides the peptide by the water you add. The powder occupies a little volume of its own, which is negligible on a typical vial but not on one with a heavy bulking agent. When a product label states a concentration, use the label’s number.

10 mL may exceed the capacity of a typical 3 mL vial. Check the vial before adding this much.

Key facts

Half-life: Not published. No accessible human pharmacokinetic study reports one, so any specific figure quoted elsewhere has no primary source behind it.
Also sold as: chorionic gonadotropin, Pregnyl, Novarel

How good is the evidence?

Approved with documented dosing by indication. One genuinely useful conflict to know about: the post-reconstitution discard window for the same molecule is 60 days refrigerated on the Pregnyl and Fresenius generic labels, but 30 days on Novarel. The drug's own label governs — not the diluent, and not a general rule of thumb.

USP units are not syringe units, and the label says intramuscular

HCG is the one product here dosed in USP units rather than milligrams, which collides badly with a syringe whose marks are also called units. They are unrelated quantities. A USP unit is a measure of biological activity defined against a reference standard; a syringe unit is one hundredth of a millilitre of liquid. Reconstitute 10,000 USP units in 10 mL and you have 1,000 USP units per millilitre, so a 500 unit dose is 0.5 mL — which is 50 syringe units. Two numbers, both called units, differing by a factor of ten in that example and by a different factor in every other.

The other instruction worth reading twice is the route. All US HCG labels specify intramuscular administration. That is not the subcutaneous route most of the other compounds on this site are given by, and it is not a detail a calculator can enforce — the arithmetic for the draw is the same either way, which is precisely why it needs stating in words.

The discard window disagrees between brands

Post-reconstitution storage for chorionic gonadotropin is published, and the three US labels do not agree with one another. Pregnyl and the Fresenius Kabi generic give 60 days refrigerated. Novarel gives 30. Same molecule, same reconstitution step, half the window.

The difference is a property of the formulation and its stability programme, not of the drug. It is also the clearest argument on this site against the habit of applying one remembered number to every vial: whichever figure you were told, there is a US label for the same molecule that says something else. The drug's own label governs — not the diluent, and not a rule of thumb.

Why the labels shout about weight loss

All US HCG labels carry, in capitals, the statement that HCG has not been demonstrated to be effective adjunctive therapy in the treatment of obesity, that there is no substantial evidence it increases weight loss beyond that resulting from caloric restriction, that it does not cause a more attractive or normal distribution of fat, and that it does not decrease the hunger and discomfort associated with calorie-restricted diets.

That paragraph is not a caution, it is a finding, and it is unusual for appearing on the label itself rather than in a separate warning. It has been there for decades and the compounded HCG diet market has continued regardless — which is worth knowing if the reason you are reconstituting a vial is weight loss.

Common questions

Sources

Every number on this page comes from one of the documents below. Where no reliable source exists, the page says so instead of filling the gap.

FDA labelFDA / DailyMed· 2023
PREGNYL (chorionic gonadotropin for injection, USP) — FDA prescribing information
FDA labelFDA / DailyMed
NOVAREL (chorionic gonadotropin for injection, USP) — FDA prescribing information
FDA labelFDA / DailyMed
Bacteriostatic Water for Injection, USP — FDA prescribing information (NDA 018802)
GuidelineInternational Organization for Standardization· 2016-03
ISO 8537:2016 — Sterile single-use syringes, with or without needle, for insulin (scope and requirements; full text not public)