# Human Chorionic Gonadotrophin (hCG): veterinary dose and monograph

> Human Chorionic Gonadotrophin (hCG) is a veterinary drug. Reproductive hormone — direct LH-like action. Indications include improvement of conception rate at AI in cattle / buffalo (luteal support); enhancement of luteal function 4–6 days post-AI; treatment of cystic ovarian disease (anoestrus / nymphomania / prolonged oestrus). This monograph lists 5 reference doses for cattle, horses and buffalo, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

Source: https://vetmasterji.com/drugs/hcg · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Veterinary drug
- **Also known as:** Chorulon, Pregnyl, Profasi
- **Species with doses:** Cattle, Horses and Buffalo
- **Routes:** IM, IV
- **Last reviewed:** 1 October 2026

## Indications

- Improvement of conception rate at AI in cattle / buffalo (luteal support)
- Enhancement of luteal function 4–6 days post-AI
- Treatment of cystic ovarian disease (anoestrus / nymphomania / prolonged oestrus)
- Induction of ovulation in mares 24 h before AI

## Human Chorionic Gonadotrophin (hCG) dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Cattle

*Human Chorionic Gonadotrophin (hCG) doses for cattle*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| At AI — luteal support | 1500 IU/cow | IM | single, at insemination | — | Withdrawal NOT established — treat as extra-label |
| Luteal function support 4–6 d post-AI | 1500 IU/cow | IM | single, 4–6 days after AI | — | Withdrawal NOT established — treat as extra-label |
| Cystic ovarian disease | 2500–5000 IU/cow | IV | single; may repeat in 14 days | — | Withdrawal NOT established — treat as extra-label |

- At AI — luteal support: Product label (Chorulon 1500 IU vial reconstituted to 5 mL): 1500 IU IM at the time of insemination. Label withdrawal: milk 0 days, meat 0 days.
- Luteal function support 4–6 d post-AI: Product label (Chorulon): 1500 IU IM 4–6 days after insemination.
- Cystic ovarian disease: Plumb’s p.268 (Follutein label): 2500–5000 U IV or 10,000 U deep IM; may repeat in 14 days if behaviour or examination indicates. Chorulon label: 3000 IU IV. Alternatively 500–2500 U injected directly into the follicle.

### Horses

*Human Chorionic Gonadotrophin (hCG) doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Induction of ovulation | 1500–3300 IU/mare | IV | single | — |

- Induction of ovulation: Plumb’s p.268: 2000–3000 U IV, preferably 6 h before mating, when a single dominant follicle over 35 mm is present (Hopkins 1987); 1500–3300 U 5–6 days after the second prostaglandin injection or on day 1–2 of oestrus (Bristol 1986). Chorulon label: 1500–3000 IU IV or IM 24 h before service.

### Buffalo

*Human Chorionic Gonadotrophin (hCG) doses for buffalo*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Ovulation induction / cystic ovaries / luteal support | 1500 IU IM at AI; 3000 IU IV for cystic ovarian degeneration | IM | single | — | Withdrawal NOT established — treat as extra-label |

- Ovulation induction / cystic ovaries / luteal support: Chorulon labels buffalo with cattle: 1500 IU IM at AI (luteal support), or 3000 IU IV for follicular/cystic ovarian degeneration. Commonly used in buffalo Ovsynch/repeat-breeder protocols.

## Contraindications

Hypersensitivity. Not for treating pregnancy diagnosis (use trans-rectal palpation or ultrasound). Repeated use can induce neutralising antibodies in some cattle — alternate with GnRH analogues for chronic / repeat-breeder cases. Pregnancy is not a contraindication per se but giving hCG to confirm pregnancy serves no clinical purpose.

## Species-specific warnings

> **Caution:** Cattle: Standard for cystic ovarian disease (3000 IU IV) and luteal support at AI (1500 IU IM). Zero milk / meat withdrawal.

> **Caution:** Horses: 1500–3000 IU IM in mares 24–36 h pre-AI for ovulation timing.

## Adverse effects

- Mild systemic reactions are rare; injection-site reactions are uncommon
- Neutralising antibodies on repeated use can blunt response over time

## Drug interactions

- GnRH analogues (buserelin, gonadorelin): both stimulate ovulation but via different mechanisms — usually NOT combined in the same protocol; alternate between cycles in repeat-breeder cases
- PGF2-alpha analogues (cloprostenol): used at different points in OvSynch / co-synch — not antagonistic, complementary
- Progesterone-releasing intravaginal devices (PRIDs / CIDRs): hCG can support luteal function after PRID withdrawal

## Pregnancy and lactation

Safe in pregnant cattle, buffalo and mares — hCG does not cross the placenta in clinically significant amounts. Zero milk / meat withdrawal per catalogue label.

## Monitoring

- Trans-rectal palpation or ultrasound 7–14 days post-injection to confirm ovulation / luteal response
- Repeat oestrus check at expected interval; treat with another option if no response
- In cystic cows, palpate ovary at 14 days post-treatment to assess cyst regression

## Clinical pearls

- OvSynch in cattle uses GnRH (buserelin / gonadorelin) rather than hCG — but hCG remains the standard "rescue" option for refractory anoestrus and post-AI luteal support
- Equine ovulation induction: 1500–3000 IU IM in the mare 24–36 h before AI to time ovulation within the breeding window
- Cystic ovarian disease in cows: 3000 IU IV is more reliable than IM for induced luteinisation
- Reconstitute only the vial you will use that day — reconstituted hCG loses potency after 24 h
- Zero milk and meat withdrawal makes hCG ideal for high-producing dairy cows

## Mechanism of action

Glycoprotein hormone with predominantly luteinising-hormone (LH)-like activity. Binds LH/CG receptors on theca and granulosa cells of the ovary — triggers final follicular maturation, ovulation, and corpus luteum formation / luteinisation. Slower onset and longer duration than endogenous LH; clinically usable to "mimic" the LH surge when natural ovulation is failing or timing needs precision (mares before AI; cystic cows for luteinisation).

## Formulations and products

- Chorulon 1500 IU lyophilized vial (MSD) — reconstitute to 5 mL = 300 IU/mL
- Chorulon (MSD Animal Health) — 1500 IU per vial (lyophilized), Lyophilized injection — reconstitute with 5 mL solvent → 300 IU/mL

## Storage

Lyophilized vials: 2–8 °C, protected from light. Reconstituted solution: refrigerate, use within 24 h; do not freeze.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Human Chorionic Gonadotrophin (hCG) for cattle?

Reference doses for Human Chorionic Gonadotrophin (hCG) in cattle: 1500 IU/cow IM single, at insemination (At AI — luteal support); 1500 IU/cow IM single, 4–6 days after AI (Luteal function support 4–6 d post-AI); 2500–5000 IU/cow IV single; may repeat in 14 days (Cystic ovarian disease). Confirm against the label and the patient before use.

### What is the dose of Human Chorionic Gonadotrophin (hCG) for horses?

Reference doses for Human Chorionic Gonadotrophin (hCG) in horses: 1500–3300 IU/mare IV single (Induction of ovulation). Confirm against the label and the patient before use.

### What is the dose of Human Chorionic Gonadotrophin (hCG) for buffalo?

Reference doses for Human Chorionic Gonadotrophin (hCG) in buffalo: 1500 IU IM at AI; 3000 IU IV for cystic ovarian degeneration IM single (Ovulation induction / cystic ovaries / luteal support). Confirm against the label and the patient before use.

### What is the withdrawal period for Human Chorionic Gonadotrophin (hCG)?

Cattle, IM (At AI — luteal support): Withdrawal NOT established — treat as extra-label; Cattle, IM (Luteal function support 4–6 d post-AI): Withdrawal NOT established — treat as extra-label; Cattle, IV (Cystic ovarian disease): Withdrawal NOT established — treat as extra-label; Buffalo, IM (Ovulation induction / cystic ovaries / luteal support): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Human Chorionic Gonadotrophin (hCG) not be used?

Hypersensitivity. Not for treating pregnancy diagnosis (use trans-rectal palpation or ultrasound). Repeated use can induce neutralising antibodies in some cattle — alternate with GnRH analogues for chronic / repeat-breeder cases. Pregnancy is not a contraindication per se but giving hCG to confirm pregnancy serves no clinical purpose.

### What are the side effects of Human Chorionic Gonadotrophin (hCG) in animals?

Mild systemic reactions are rare; injection-site reactions are uncommon; Neutralising antibodies on repeated use can blunt response over time.

## Sources

- MSD Animal Health Blue Cross Book 31/2015 — Chorulon, p. 115
- Plumb's Veterinary Drug Handbook

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.