HCG is the hormone your body uses to keep the corpus luteum alive during pregnancy. It is also what keeps your testes from shrinking on testosterone therapy, what some fertility protocols use to trigger ovulation, and what the controversial Simeons diet claimed could reset weight. The science is real. Some of the marketing around it is not.
🔑 Key Takeaways
- HCG (human chorionic gonadotropin) is a 237-amino-acid glycoprotein hormone naturally produced by the placenta during pregnancy. It is made of alpha and beta subunits, with the beta subunit unique to HCG
- HCG activates the LH (luteinizing hormone) receptor because it shares the same alpha subunit as LH, FSH, and TSH. This is why HCG stimulates the same testicular and ovarian responses that LH does
- FDA-approved uses: induction of ovulation in female fertility treatment, hypogonadism in men (stimulates testicular testosterone production), and undescended testicles in prepubertal males
- Most common off-label use in 2026: testicular preservation during testosterone replacement therapy (TRT), typically 250 to 500 IU subcutaneously 2 to 3 times weekly
- The Simeons weight-loss protocol (HCG plus very-low-calorie diet) is not supported by evidence. Controlled trials show the weight loss comes from the caloric restriction alone. The FDA has issued warnings against HCG weight-loss products
- Side effects are generally mild at TRT-adjunct doses: injection site reactions, mild water retention, occasional acne or increased libido. Higher doses can produce more pronounced androgenic effects
- Not for use in patients with hormone-sensitive cancers (prostate, breast), women with PCOS without physician supervision, or those with undiagnosed abnormal vaginal bleeding
- Prescription-only. Sold under brand names like Pregnyl, Novarel, and Ovidrel, with generic HCG also available
This page covers HCG peptide comprehensively: what it is, the natural pregnancy biology, every FDA-approved and off-label use, TRT protocols, side effects, contraindications, the Simeons diet controversy, and how it compares to other fertility and hormone peptides.
What Is HCG?
A pregnancy hormone with wide medical applications.
HCG stands for human chorionic gonadotropin. It is a glycoprotein hormone made up of two subunits: an alpha subunit (identical to the alpha subunit of LH, FSH, and TSH) and a beta subunit that is unique to HCG and gives it its specific activity. The full HCG molecule is 237 amino acids across both subunits combined, which makes it much larger than typical peptides.
HCG at a Glance
- Full name: Human chorionic gonadotropin
- Structure: Glycoprotein with alpha and beta subunits (237 amino acids total)
- Produced by: Placental syncytiotrophoblast cells during pregnancy
- Natural role: Maintains the corpus luteum in early pregnancy, signals the uterus to support implantation
- Receptor activated: LH (luteinizing hormone) receptor
- Brand names: Pregnyl, Novarel, Ovidrel, Profasi (some discontinued)
- FDA status: Approved for fertility treatment, hypogonadism, cryptorchidism
- Administration: Subcutaneous or intramuscular injection
HCG is used in medicine and athletic/biohacking contexts for one core reason: it mimics LH. Because HCG and LH activate the same receptor, HCG can drive testicular testosterone production in men, trigger ovulation in women, and maintain the same downstream signaling that natural LH would. But HCG has a much longer half-life in the bloodstream than LH, which makes it clinically practical where pulsatile LH dosing would not be.
How HCG Works
Via the LH receptor, with a longer half-life than native LH.
The mechanism is straightforward despite HCG's clinical versatility:
- LH receptor binding: The beta subunit of HCG provides specificity for the LH receptor, while the shared alpha subunit allows signal transduction. HCG binds and activates the same LH receptor that native LH binds.
- In men (testes): LH receptor activation on Leydig cells stimulates testosterone production. HCG doses in the hundreds of IU range produce measurable testosterone increases and preserve testicular volume during exogenous testosterone therapy.
- In women (ovaries): LH receptor activation triggers final ovulation when administered at the right point in the menstrual cycle, which is why HCG is used as an "ovulation trigger" in IVF protocols.
- Long half-life: HCG has a plasma half-life of about 24 to 36 hours, dramatically longer than LH's approximately 20 minutes. This allows weekly or bi-weekly dosing schedules.
- No direct anabolic or caloric effect: HCG does not directly burn fat, build muscle beyond what its testosterone-supporting action does, or reset metabolism.
HCG Benefits and FDA-Approved Uses
Female fertility treatment (ovulation induction)
One of HCG's original and primary approved uses. In fertility protocols, HCG is given as an ovulation trigger after ovarian stimulation with clomiphene, letrozole, or injectable gonadotropins. A typical ovulation trigger dose is 5,000 to 10,000 IU administered 36 hours before planned insemination or egg retrieval. This is an acute, single-dose use.
Male hypogonadism
For men with secondary hypogonadism (low testosterone due to insufficient pituitary LH signaling), HCG can restore testicular testosterone production. Standard protocols use 500 to 4,000 IU 2 to 3 times weekly depending on the clinical goal and starting testosterone level.
Testicular preservation during TRT (off-label, widely used)
This is the most common HCG use in 2026. Men on testosterone replacement therapy lose endogenous testicular testosterone production because exogenous testosterone suppresses LH via the HPG axis feedback loop. This causes testicular atrophy and loss of fertility. Adding HCG to a TRT protocol mimics LH signaling directly at the testes, preserving testicular volume, maintaining some endogenous testosterone production, and preserving fertility.
Typical TRT-adjunct dose: 250 to 500 IU subcutaneously 2 to 3 times weekly. Higher doses (up to 1,000 IU) are occasionally used for men who want stronger fertility preservation.
Post-cycle therapy (PCT) in performance-enhancing drug use
For men coming off anabolic steroid cycles, HCG is used to restart testicular function before or during a PCT protocol that includes SERMs (selective estrogen receptor modulators) like clomiphene or enclomiphene. This is off-label use and occurs in bodybuilding communities. Protocols vary widely.
Cryptorchidism (undescended testicles) in boys
A less common but FDA-approved pediatric use. HCG has been used to stimulate testicular descent in prepubertal boys with cryptorchidism, though surgical correction has largely replaced hormonal treatment for most cases.
What HCG is NOT used for legitimately: Simeons weight-loss protocol
The Simeons diet, developed by Dr. A.T.W. Simeons in the 1950s, pairs low-dose HCG injections with a very-low-calorie diet (500 kcal/day) and claims dramatic weight loss. Controlled clinical trials have repeatedly shown that the weight loss in this protocol is entirely attributable to the severe caloric restriction, not to HCG. The FDA has issued multiple warnings about HCG weight-loss products, which often contain little or no active HCG and are sold illegally as dietary supplements.
In short: yes, people lose weight on the Simeons protocol, because they are eating 500 calories a day. HCG provides no additional metabolic benefit. Weight loss of the same magnitude can be achieved through caloric restriction alone, without the hormonal side effects.
HCG Dosage
HCG Dosing Protocols
- TRT testicular preservation: 250 to 500 IU subcutaneously, 2 to 3 times weekly
- Male hypogonadism: 500 to 4,000 IU 2 to 3 times weekly (physician-directed)
- Ovulation trigger (IVF): 5,000 to 10,000 IU single dose, timed 36 hours before retrieval
- Post-cycle therapy: 500 to 1,000 IU every 3 to 4 days for 2 to 4 weeks (off-label, highly variable)
- Cryptorchidism: 1,000 to 4,000 IU twice weekly for 5 to 10 doses (pediatric, physician-directed)
Reconstitution
HCG is sold as a lyophilized powder with accompanying bacteriostatic water or sodium chloride diluent. A common format is 5,000 IU per vial. Reconstituted with 5 mL gives 1,000 IU/mL. A 500 IU dose is 0.5 mL (50 units on a U-100 insulin syringe). Always follow the specific manufacturer's reconstitution instructions.
Administration
- Route: Subcutaneous (most common for TRT use) or intramuscular (traditional for fertility use)
- Injection sites: Abdomen, thigh, or upper arm for subcutaneous. Glutes or deltoids for intramuscular
- Rotation: Rotate sites to prevent local irritation
- Timing: Morning or evening, consistent day-of-week scheduling
Storage
- Lyophilized vial: Refrigerate at 2 to 8°C. Do not freeze
- Reconstituted: Refrigerate. Use within 30 to 60 days depending on manufacturer (shorter windows for bacteriostatic water, longer for sodium chloride)
- Protect from light
HCG Side Effects
| Side effect | Frequency | Notes |
|---|---|---|
| Injection site reaction | Common | Mild redness or soreness, resolves within hours |
| Mild water retention | Common | Mild aromatization of the testosterone HCG produces |
| Increased libido | Common | Therapeutic effect for many patients, may be unwelcome for some |
| Acne | Occasional | More common at higher doses due to increased testosterone |
| Mood changes | Occasional | Typically positive but variable |
| Mild headache | Uncommon | Usually first week, resolves |
| Gynecomastia (male) | Rare at low doses | Higher doses increase aromatization to estrogen. Monitor and consider aromatase inhibitor if needed |
| Ovarian hyperstimulation syndrome (OHSS) | Specific to fertility use | Risk in women undergoing ovarian stimulation. Monitored by fertility specialists |
| Multiple pregnancy (female) | Fertility use | Increased risk of twins/triplets in ovulation induction protocols |
Long-term use at TRT-adjunct doses is generally well-tolerated. High-dose use (post-cycle therapy, fertility treatment) carries more pronounced side effects but is typically short-duration.
Who Should Not Use HCG
Do NOT Use HCG If You Have:
- Hormone-sensitive cancer: Prostate cancer, androgen-sensitive cancers in men; breast, ovarian, uterine cancers in women
- Undiagnosed abnormal vaginal bleeding (women): HCG is contraindicated until the bleeding is evaluated
- Precocious puberty (children)
- Pituitary tumor or prior pituitary surgery: Use requires endocrinologist consultation
- Thyroid or adrenal dysfunction: Must be stabilized first
- Known hypersensitivity to HCG or any component of the formulation
HCG vs Other Fertility and Hormone Peptides
| Peptide / Hormone | Mechanism | Best for |
|---|---|---|
| HCG | LH receptor agonist | Testicular support on TRT, fertility (ovulation trigger), PCT |
| Gonadorelin (GnRH) | Stimulates pituitary to release LH and FSH | Upstream TRT adjunct, alternative to HCG |
| Clomiphene (Clomid) | SERM, increases natural LH via HPG feedback | Post-cycle therapy, secondary hypogonadism |
| Enclomiphene | Cleaner SERM isomer, similar to clomiphene | TRT alternative in secondary hypogonadism |
| FSH (follicle-stimulating hormone) | Direct FSH receptor agonist | Fertility treatment (female stimulation) |
| Kisspeptin | GnRH-stimulating upstream hormone | Research / emerging fertility applications |
HCG and gonadorelin are the two common TRT adjuncts for testicular preservation. They work at different levels of the HPG axis: HCG at the testes directly, gonadorelin at the pituitary. Physicians choose between them based on cost, pharmacokinetics, and patient response. See our kisspeptin page and gonadorelin guide for more on alternatives.
HCG Stacks
- HCG + Testosterone (TRT): Standard men's health stack. Testosterone provides systemic androgenic effect; HCG preserves testicular function and fertility.
- HCG + Enclomiphene: Alternative PCT approach for men coming off TRT or steroid cycles. Enclomiphene restores natural HPG signaling while HCG maintains testicular responsiveness.
- HCG + Anastrozole (aromatase inhibitor): Used when higher HCG doses produce unwanted aromatization and estrogen elevation. Physician-directed.
- HCG + FSH: Fertility treatment combination for men with both LH and FSH deficiency. Physician-directed.
All HCG stacks should be physician-supervised. HCG is a prescription hormone and the stacks interact with endocrine function in ways that benefit from lab monitoring.
Regulatory Status and Where to Buy
HCG is prescription-only in the US. It is available as brand-name products (Pregnyl, Novarel, Ovidrel) and as generic HCG through licensed compounding pharmacies. Standard acquisition path is a physician prescription filled at a retail or mail-order pharmacy.
Avoid unregulated "HCG drops" or "homeopathic HCG" sold as dietary supplements. These often contain no active HCG. The FDA has issued multiple enforcement actions against such products.