The questions below are the ones researchers ask most about storing, mixing and handling HCG. Each answer reflects what HCG is, a two-subunit glycoprotein hormone measured in international units, and links to the fuller page where there is one.
How long does HCG last in the fridge after mixing?
Mixed with bacteriostatic water and kept at 2 to 8 °C in the dark, HCG lasts 8 to 12 weeks under Vistara Labs’ handling guidance, with quality slowly fading from around week 6 to 8. No published study gives a refrigerated window for hCG in bacteriostatic water, so the window is general guidance. One supplier gives 2 to 7 days at 4 °C for its additive-free hCG in pure water, a cautious figure for an unpreserved solution. The full table is on how long HCG lasts.
How long does unmixed HCG powder last?
The WHO reference standard is stored at minus 20 °C and has no expiry date assigned, and it showed no significant loss in accelerated heat testing. One supplier rates its lyophilised hCG as stable at room temperature for 3 weeks, stored desiccated below minus 18 °C for the long term. The powder is hygroscopic, so it is kept sealed and dry, and it ships without an ice pack.
Why is HCG measured in IU instead of milligrams?
Because its sugar chains vary from molecule to molecule, so weight does not track activity closely. HCG is calibrated in international units against a WHO International Standard; the 5th standard, NIBSC 07/364, carries 179 IU per ampoule for immunoassays and 162 IU for bioassays.
What makes HCG lose activity in solution?
Mainly its two subunits coming apart. They are held together without a covalent bond, and warmth separates them: over 72 hours, separation was undetectable at 3 °C and measurable at 20 °C (Sancken and Bahner, Prenatal Diagnosis, 1995). Acid, foam, freezing and enzymes from contamination add to it. The details are on the HCG stability page.
What do you mix HCG with?
Bacteriostatic water, which is sterile water with 0.9% benzyl alcohol so a refrigerated vial can be accessed more than once. HCG is a hydrophilic glycoprotein and dissolves fully in it with gentle swirling, without acid or other solvents. The reasons are on the HCG solubility guide.
How much bacteriostatic water goes in a 5000 IU HCG vial?
There is no single correct volume. With 2 mL a 5000 IU vial gives 2500 IU/mL; with 1 mL it gives 5000 IU/mL. More water spreads the same amount of hormone through a larger volume, so write the chosen concentration on the vial. The tables are on the HCG reconstitution page.
Should HCG be dissolved in acetic acid?
No. Dilute acetic acid is used in labs for hydrophobic or basic peptides that resist water, but HCG dissolves readily without it. Low pH also separates hCG into its subunits, which then take many hours to recombine, so acid works directly against the hormone.
Why is my HCG cloudy after mixing?
Brief cloudiness that clears within 10 to 15 minutes is usually trapped air from adding water too fast or shaking. Foam matters more for a protein than for a short peptide, because proteins unfold at air and liquid surfaces. Haze that persists, strands, particles or a tint that appear later point to warm storage, freezing or contamination, and the solution is discarded. More in why peptides gel or go cloudy.
Can you freeze mixed HCG?
Not a vial that will be opened again. One supplier asks users to prevent freeze-thaw cycles, repeated freezing and thawing promotes aggregation in protein solutions, and each thaw warms the solution through the range where the subunits separate. Laboratories that need frozen solution divide it into single-use aliquots and thaw each one once. Sealed powder can be frozen at minus 20 °C without concern.
Does HCG need to be kept out of the light?
HCG has no tryptophan, the residue that absorbs ultraviolet light most strongly, so it is less light-sensitive than many proteins, though its methionines can oxidise. Keeping the vial boxed in the dark is still standard practice. It also keeps the vial away from warmth, which matters more for this hormone.
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
