Carl read the papersWhat it actually is
Human chorionic gonadotropin is a hormone produced in pregnancy. Structurally it closely resembles luteinising hormone (LH) — the pituitary signal that tells the testes to produce testosterone.
That resemblance is the entire point. When exogenous testosterone suppresses the body's own LH, the testes lose their signal and shut down — with testicular atrophy and loss of fertility following. HCG substitutes for the missing signal directly at the testes.
It is a genuinely approved prescription drug for hypogonadism and fertility, sold in international units rather than milligrams.
How it’s thought to work
- LH receptor agonism — Binds LH receptors on the Leydig cells of the testes, driving testosterone production directly.
- Bypasses the pituitary — Works downstream of the suppressed signal, which is why it functions while the HPTA axis is shut down.
- Maintains testicular volume — Keeps the tissue active, which is what prevents the atrophy that follows unopposed testosterone use.
- Preserves spermatogenesis — The fertility argument — intratesticular testosterone is what sperm production requires, and exogenous testosterone does not supply it.
What the research says
Unusually for this directory, this is established medicine rather than research chemistry. HCG is approved for hypogonadotropic hypogonadism and for fertility use, with decades of clinical use behind it. Its use alongside testosterone therapy to preserve testicular function and fertility is well documented in the andrology literature.
- Approved prescription drug — hypogonadotropic hypogonadism and fertility indications.
- Well documented for preserving testicular volume and spermatogenesis during testosterone therapy.
- Also used in post-cycle restart protocols to restore the suppressed axis.
- Dosed in international units (IU), not milligrams — a 5,000 IU vial is the common presentation.
Watch: HCG explained
Video by Balance My Hormones on YouTube. Not affiliated with Peptide Carl and not an endorsement — included because a second explanation of the same mechanism is often what makes it click.
Reported protocols
These are the doses the peptide community actually reports running (Reddit & forums), alongside published research — logged for education, not as a recommendation to use.
| Parameter | Commonly reported range |
|---|---|
| Alongside TRT | Commonly reported at 250–500 IU two to three times weekly, to maintain testicular function |
| Restart protocols | Higher and shorter — often 1,000–2,500 IU every other day for a limited run, then tapered |
| Reconstitution | A 5,000 IU vial in 5 mL BAC water gives 1,000 IU/mL, so 25 units on a U-100 syringe is 250 IU |
| Route | Subcutaneous or intramuscular — subcutaneous is the more commonly reported |
| Frequency | Split, frequent, small doses are consistently preferred over large infrequent ones |
| Community tip | The dominant reported error is dosing too high. Excessive HCG desensitises the Leydig cells and can raise oestradiol sharply — the small-and-frequent pattern exists because people learned this the hard way. |
Common use cases
| Goal | Community protocol notes |
|---|---|
| Alongside testosterone therapy | 250–500 IU 2–3×/week to maintain testicular function and fertility |
| Post-cycle restart | higher, shorter, tapered — restoring a suppressed axis |
| Fertility preservation | maintaining intratesticular testosterone, which exogenous testosterone does not supply |
Mixing it (reconstitution)
Freeze-dried peptides must be reconstituted with bacteriostatic water before they can be measured. Carl’s calculator turns “mg in the vial + ml of water + target dose” into “units on the syringe” — and tells you how long the vial lasts.
→ Open the Reconstitution Calculator
Injection & handling
Subcutaneous is the more commonly reported route, though intramuscular is also used. A 5,000 IU vial reconstituted with 5 mL BAC water gives 1,000 IU/mL — so 25 units on a U-100 insulin syringe is 250 IU. Reported use alongside testosterone therapy sits around 250–500 IU two to three times weekly; restart protocols run higher and shorter. Reconstituted HCG needs refrigeration and is generally used within about 30 days. The consistent message is that more is not better — too much desensitises the receptors it is meant to be stimulating.
Stacks it appears in
- With testosterone therapy — The standard pairing — HCG supplies the testicular signal that exogenous testosterone removes.
- With gonadorelin — A different approach to the same problem: gonadorelin acts on the pituitary, HCG acts at the testes directly.
