Chorionic Gonadotropin (HCG)
Human Chorionic Gonadotropin
Also known as: Chorulon · Chorionad · P.G. 600 · Profasi · Choron 10 · Gonic · Novarel · Pregnyl · human chorionic gonadotropin · hCG · LH 500 · chorionic gonadotrophin · dynatropin · pregnancy-urine hormone · PU
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Cryptorchidism | 500 Units injected twice weekly | IM/SC | twice weekly | 4-6 weeks | 🌎 NA |
| HCG Challenge test (Male dogs or females with suspected sexual differentiation disorder) | 44 micrograms/kg | IM | once | — | 🌎 NA |
| HCG Challenge test (Female dogs to diagnose functional ovarian tissue) | 100-1000 Units | IM | once | — | 🌎 NA |
| To produce luteinization of a persistent follicular cyst | 500 Units | IM | repeat in 48 hours | — | 🌎 NA |
| Infertile bitches cycling normally with low progesterone due to lack of corpus luteum formation | 500 Units | SC | once | — | 🌎 NA |
| Male infertility secondary to low testosterone, LH and FSH | 500 Units | SC | twice weekly | 4 weeks | 🌎 NA |
- HCG Challenge test (Male dogs or females with suspected sexual differentiation disorder): Take sample for resting testosterone level. Administer HCG and take a 4 hour post sample.
- HCG Challenge test (Female dogs to diagnose functional ovarian tissue): Give during apparent estrous episode. Measure progesterone level in 5-7 days. >1 ng/mL indicates functional tissue.
- To produce luteinization of a persistent follicular cyst: If effective, will convert from proestrus to estrus in 1-2 days and sexual behavior should stop within 2 weeks.
- Infertile bitches cycling normally with low progesterone due to lack of corpus luteum formation: Give on days 10-11 of heat cycle or when vaginal smear indicates breeding readiness. Breed 2 days after administration.
- Male infertility secondary to low testosterone, LH and FSH: Add PMSG 20 Units/kg SC 3 times weekly. Continue for 3 months. Once spermatogenesis ensues, may continue with HCG only.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| HCG Challenge test (Male cats or females with suspected sexual differentiation disorder) | 250 micrograms | IM | once | — | 🌎 NA |
| HCG Challenge test (Queens to diagnose functional ovarian tissue) | 50-100 Units | IM | once | — | 🌎 NA |
| Infertility, reduced libido, testis descent in male cats | 50-100 Units | IM/SC | repeated if necessary | — | 🌎 NA |
| Infertility in queens due to confirmed ovulation failure | 100-500 Units | IM | once | — | 🌎 NA |
| To induce ovulation in anestrus queens | 250 micrograms | IM | once daily for 2 days | 2 days | 🌎 NA |
| After artificial insemination | 50-75 Units | IM | immediately after insemination; repeat in 24 hours | 24 hours | 🌎 NA |
- HCG Challenge test (Male cats or females with suspected sexual differentiation disorder): Take sample for resting testosterone level. Administer HCG and take a 4 hour post sample.
- HCG Challenge test (Queens to diagnose functional ovarian tissue): Give during apparent estrous episode. Measure progesterone level in 5-7 days. >1 ng/mL indicates functional tissue.
- To induce ovulation in anestrus queens: Give FSH-P 2 mg IM daily until estrus is observed. Give HCG on first and second day of estrus.
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Cystic ovaries (Guinea pigs) | 1000 Units/animal | IM | repeat in 7-10 days | — | 🌎 NA |
Ferrets
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Estrus management | 100 Units | IM | repeat in 1 week as necessary | — | 🌎 NA |
- Estrus management: Most effective 14 days after onset of estrus.
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| To reduce feather plucking (especially in female birds) | 500-1,000 Units/kg | IM | once | — | 🌎 NA |
- To reduce feather plucking (especially in female birds): Dosage is empirical. If no response in 3 days, repeat. If reduces feather plucking, will need to repeat after 4-6 weeks. Repeated usage reduces time between treatments.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Cryptorchidism (Foals) | 1000 Units | IM/SC | twice weekly | 4-6 weeks | 🌎 NA |
| To induce ovulation in early estrus (dominant follicle >35 mm) | 2000-3000 Units | IV | once | — | 🌎 NA |
| Treatment of persistent follicles during the early transition period | 1000-5000 Units | IM/IV | once | — | 🌎 NA |
| To hasten ovulation and reduce variability of estrus after prostaglandin synchronization | 1500-3300 Units | IM/IV | once | — | 🌎 NA |
- Cryptorchidism (Foals): Note: Many clinicians believe that medical treatment is unwarranted and that surgery should be performed.
- To induce ovulation in early estrus (dominant follicle >35 mm): Preferable to treat mare 6 hours before mating.
- Treatment of persistent follicles during the early transition period: Results are variable.
- To hasten ovulation and reduce variability of estrus after prostaglandin synchronization: Give 5-6 days after the second prostaglandin treatment or on the first or second day of estrus.
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Treatment of ovarian cysts | 10,000 Units deep IM or 2500-5000 Units IV. Alternatively, 500-2500 Units injected directly into the follicle. | IM/IV/Intrafollicular | once | — | 🌎 NA |
- Treatment of ovarian cysts: May repeat in 14 days if animal's behavior or physical exam indicates a need for retreatment.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Chorionic Gonadotropin (HCG) is a gonad-stimulating polypeptide hormone obtained from the urine of pregnant women. It is widely used in veterinary theriogenology across multiple species.
Key Clinical Uses:
- Cattle: Treatment of nymphomania due to cystic ovaries.
- Dogs & Cats: HCG challenge testing to diagnose retained testicular tissue (cryptorchidism) or functional ovarian tissue (ovarian remnant syndrome).
- Horses: Induction of ovulation and management of persistent follicles.
- Exotics: Management of estrus in ferrets, cystic ovaries in guinea pigs, and empirical treatment for feather plucking in birds.
Clinical Pearl: Because HCG is a large, foreign human protein, repeated administration in veterinary patients can lead to the formation of neutralizing antibodies, which may progressively diminish its clinical efficacy over time.
Mechanism of action
HCG is a glycoprotein that primarily mimics the action of luteinizing hormone (LH), with minor follicle-stimulating hormone (FSH)-like activity.
- In Males: Binds to LH receptors on testicular interstitial (Leydig) cells → stimulates differentiation and androgen (testosterone) production → promotes testicular descent and spermatogenesis.
- In Females: Binds to LH receptors on the ovary → stimulates the corpus luteum to produce progesterone → triggers ovulation of mature follicles. In bitches, it also induces estrogen secretion.
Safety & warnings
Contraindications
- Androgen-dependent neoplasias (e.g., prostatic carcinoma)
- Precocious puberty
- Known hypersensitivity to HCG
- Pregnancy (FDA Category X in humans, unless specifically indicated for reproductive management)
Adverse effects
- Hypersensitivity reactions / Anaphylaxis
- Pain at the injection site
- Antibody production leading to diminished efficacy (with repeated use)
- Abortion in mares if given prior to the 35th day of pregnancy
- Gynecomastia, headache, depression, irritability, and edema (reported in humans)
Precautions
Warning: Antibody production to this hormone has been reported after repetitive use, resulting in diminished effect.
- Pregnancy: FDA Category X in humans (risk of use clearly outweighs any possible benefit). May cause abortion in mares prior to the 35th day of pregnancy due to increased estrogen levels.
- Administration: Must be given parenterally; it is destroyed in the GI tract if given orally.
Monitoring
- Testosterone levels (for HCG challenge test in males)
- Progesterone levels (for HCG challenge test in females)
- Resolution of clinical signs (e.g., cessation of estrus behavior, resolution of cystic ovaries)
- Signs of hypersensitivity or anaphylaxis post-injection
Pharmacokinetics
Absorption
Destroyed in the GI tract after oral administration; must be given parenterally. After IM injection, peak plasma levels occur in about 6 hours.
Distribution
Distributed primarily to the ovaries in females and to the testes in males. Some may also be distributed to the proximal tubules in the renal cortex.
Elimination
Eliminated from the blood in a biphasic manner. The initial elimination half-life is about 11 hours and the terminal half-life is approximately 23 hours.
Overdose
No overdosage cases have been reported with HCG in veterinary medicine.
Available products
Formulations
- Powder for injection (lyophilized)
Veterinary
- Chorionic Gonadotropin (HCG) Injection: 10,000 Units per vial (Chorulon, Chorionad)
- Chorionic Gonadotropin freeze-dried powder: P.G. 600 (contains PMSG 400 Units + hCG 200 Units, or PMSG 2,000 Units + hCG 1,000 Units)
Human-labeled
- Chorionic Gonadotropin Powder for Injection: 5,000 Units/vial, 10,000 Units/vial, 20,000 Units/vial (Profasi, Choron 10, Gonic, Novarel, Pregnyl, generic)
Regulatory status
Withdrawal times: cattle meat 0 days · cattle milk 0 days
POM-V classification.
Withdrawal times: cattle meat 0 days · cattle milk 0 days
POM-V (Prescription Only Medicine - Veterinarian).
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store powder at room temperature (15-30°C) and protect from light. After reconstitution, the solution is stable for 30-90 days when stored at 2-15°C (refrigerated). However, veterinary labels (Chorulon, P.G. 600) state to use the vial immediately after reconstituting.
Client information
- Administration: This medication must be given by injection. It is not effective if given by mouth.
- Side Effects: Your pet may experience mild pain or swelling at the injection site.
- Allergic Reactions: Watch closely for signs of an allergic reaction, such as facial swelling, hives, or difficulty breathing, and contact your veterinarian immediately if these occur.
- Long-term Use: If this medication is used repeatedly over a long period, your pet's body may develop antibodies against it, making it less effective over time.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.