What Is HCG? Dosage, Half-Life & How to Track It
Also known as: Human Chorionic Gonadotropin · Pregnyl · Novarel · hCG
HCG (human chorionic gonadotropin) mimics luteinizing hormone (LH), binding the same receptors in the testes to keep them producing testosterone and sperm even while exogenous testosterone suppresses your pituitary. A common maintenance protocol on TRT is 500 IU subcutaneously, three times a week (about 1,500 IU/week total). Its half-life is long for a peptide hormone — roughly 36 hours — which is why a few shots a week is enough to keep it working. Educational only; hCG dosing on or off TRT should be set with a prescriber.
What HCG is and how it works
HCG is a glycoprotein hormone structurally similar enough to luteinizing hormone (LH) that it binds the same LH receptors in the testes (and ovaries). In men, that means it drives the Leydig cells to keep producing testosterone — and to keep the testes their normal size and function — through a pathway that does not depend on the pituitary at all.
That last point is the whole reason hCG shows up in TRT protocols. Exogenous testosterone raises blood levels enough that the pituitary’s negative-feedback loop shuts down its own LH and FSH output, which is what causes testicular atrophy and fertility loss on TRT. Because hCG acts directly on the testes rather than through the pituitary, it bypasses that shutdown and keeps the testes running even while natural LH is suppressed.
At higher doses, the same mechanism is used for fertility restoration and post-cycle recovery, sometimes paired with an FSH source like HMG — LH activity alone maintains testosterone and size, but full spermatogenesis needs FSH too.
Typical dosing & reconstitution
The standard TRT-maintenance approach is 500 IU subcutaneously three times a week (e.g., Monday/Wednesday/Friday), for a weekly total around 1,500 IU. Higher-dose protocols exist for post-cycle recovery or more significant suppression, but that’s a different use case with different monitoring.
HCG comes as a lyophilized powder reconstituted with bacteriostatic water:
| Vial | BAC water | Concentration | 1 unit ≈ |
|---|---|---|---|
| 5,000 IU | 2 mL | 2,500 IU/mL | 25 IU |
At 2,500 IU/mL, a 500 IU dose is 20 units on a U-100 insulin syringe — 250 IU works out to 10 units. Reconstituted hCG holds up well refrigerated, commonly cited for up to 60 days.
Half-life & what it means for frequency
HCG’s half-life — roughly 36 hours — is unusually long for a peptide hormone, and longer than LH’s own half-life of about 30 minutes. That difference is deliberate: it’s what lets a few injections a week sustain LH-receptor stimulation instead of requiring something closer to LH’s natural pulsatile release.
It also means hCG doesn’t need to chase a tight schedule the way a short-half-life peptide does — a dose landing a few hours early or late barely moves the exposure curve across the week.
What to track & common side effects
Reported side effects are generally mild and dose-related: water retention, injection-site irritation, mood changes, and — at higher or prolonged doses — a rise in estradiol, since more testosterone substrate means more aromatization. That’s one reason estradiol is often tracked alongside testosterone on protocols that include hCG.
What’s worth logging is straightforward: each injection with its dose, and the labs your prescriber is watching — testosterone, estradiol, and, if fertility is the goal, semen parameters over time. hCG is usually one piece of a larger TRT or fertility protocol, so it’s most useful tracked next to the rest of it rather than in isolation.
How to track HCG in Stackeddd
Log each hCG injection alongside your testosterone shots so the two-drug protocol lives in one place instead of two mental notes. The 3×/week rhythm is easy to lose track of on its own — a logged streak makes the pattern visible, and the reconstitution math is a one-time setup.
Model it yourself · free, no account
Reconstitution Calculator
Model it yourself: enter your vial size (IU) and BAC water, and the Peptides tab returns concentration and exact insulin-syringe units for any dose — the same math built into the Stackeddd app.
Related compounds
Related reading: TRT Math: what mg/mL actually means · Peptide reconstitution math: how much BAC water to add
Frequently asked questions
What does hCG do on TRT?
It mimics LH, directly stimulating the testes to keep producing testosterone and maintaining testicular size and function — a job the pituitary would normally do, but can’t while exogenous testosterone has it suppressed.
What is the half-life of hCG?
Roughly 36 hours — long enough that a few injections a week (commonly 500 IU three times weekly) sustain LH-receptor stimulation, unlike natural LH, which the body releases in short pulses with a half-life of about 30 minutes.
How do you reconstitute hCG?
Add bacteriostatic water to the lyophilized vial — a common setup is 2 mL into a 5,000 IU vial, giving 2,500 IU/mL, so a 500 IU dose is 20 units on a U-100 insulin syringe. The reconstitution calculator handles any vial-and-water combination.
Is hCG the same as testosterone?
No — hCG doesn’t contain testosterone. It’s a signaling hormone that tells the testes to make their own, which is why it’s used to prevent testicular shutdown during TRT rather than as a testosterone source itself.
This is educational information, not medical advice. Doses and protocols above reflect published references and community practice — protocol decisions belong with your prescribing physician. Generic names used throughout. How this reference is built & how the AI is tested →
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