What HCG is
Human chorionic gonadotropin is an LH-mimicking hormone, FDA approved for fertility indications and prescribed off-label alongside testosterone therapy to maintain testicular function and fertility. It is one of the few compounds here with a long clinical history and real prescribing conventions to anchor on.
Vials are dosed in international units and come large (5,000 and 10,000 IU are standard), so a single reconstitution covers many small doses. The PTDS dataset includes repeated freeze-thaw and storage tests on HCG specifically because users stretch one vial across weeks.
Reconstitution math
Concentration is everything: the same 5,000 IU vial gives a different draw for every amount of bacteriostatic water you add. The table uses the common 2 mL setup for each vial size, which puts every unit on a U-100 insulin syringe at 25 IU for the default vial. Dashes mark draws too small to measure or larger than the syringe.
| Vial | BAC water | Concentration | 250 IU | 500 IU | 1,000 IU |
|---|---|---|---|---|---|
| 5,000 IU | 2 mL | 2,500 IU/mL | 10 u | 20 u | 40 u |
| 10,000 IU | 2 mL | 5,000 IU/mL | 5 u | 10 u | 20 u |
Dosing and protocol
Common adjunct protocol: 250 to 500 IU two to three times weekly; fertility and monotherapy protocols run higher under clinical supervision.
The common adjunct protocol is 250 to 500 IU two to three times weekly. With a 5,000 IU vial in 2 mL of bacteriostatic water, 250 IU is a clean 10-unit draw. Its 33-hour terminal half-life is long for a peptide hormone but short enough that every-other-day or twice-weekly injections produce meaningful peaks and troughs rather than a flat level.
Pharmacokinetics
HCG has published human pharmacokinetics: biphasic elimination with a terminal half-life around 33 hours; peak roughly 12 to 24 hours after a subcutaneous dose. The curves below are normalized one-compartment models built from the cited half-life, the same math the Planner uses. They show shape and timing, not absolute blood levels.
Storage and handling
Lyophilized vials keep best cold, dark, and dry; refrigeration is the community default and freezing lyophilized powder is common for long holds. After reconstitution, refrigerate at 2 to 8 C, do not freeze the solution, and date the vial. Bacteriostatic water's preservative keeps multi-dose use practical for about 28 days by USP convention, though our 120-day stability study found the preservative itself outlasts that window.
Labeled guidance for reconstituted HCG is refrigeration with use windows of 30 to 60 days depending on the product. PTDS freeze-thaw testing on HCG found the hormone tolerant of careful handling, but the refrigerate-and-date rule remains the default.
Got a certificate of analysis with your vial? Run it through our COA Reader: it reads the report in plain English, checks purity and mass against the label claim, and links the testing lab’s own verification page. Our guide to reading a COA explains what the numbers do and do not tell you.
Sources
- Pregnyl prescribing information (Organon)
- Saal et al., Pharmacokinetics of hCG after intramuscular and subcutaneous administration, Fertil Steril 1991
- Hsieh et al., Concomitant hCG preserves spermatogenesis during testosterone therapy, J Urol 2013