Prescribing medication is an important part of veterinary care, but prescription rules differ by state. Every prescription must meet legal requirements to ensure medications are used safely and correctly. In Illinois, veterinarians must follow both state and federal rules for writing, recording, and dispensing prescriptions. If state and federal laws differ, the stricter rule applies. Often, Illinois law is stricter.
Familiarity with these regulations helps veterinarians and pharmacists collaborate to deliver safe, legal, and effective animal care. This article summarizes the main prescription requirements in Illinois. For full legal information, consult the original statutes. Regulations differ in other states.
DVMs and NPIs
National Provider Identifier (NPI) numbers are given only to those who bill for human medical services. As a result, veterinarians do not have or need an NPI number to prescribe or dispense medications.
If a pharmacy requests an NPI number on a veterinary prescription, the veterinarian should provide their state veterinary license number and, if necessary, their DEA registration number for controlled substances. Pharmacists should be aware that veterinarians are licensed differently and do not have NPIs. If pharmacy staff refuse to process a prescription, the American Veterinary Medical Association advises veterinarians to email the staff member’s name, the pharmacy’s name, store number, and location to NPI@avma.org. and provide the. For more information, refer to avma.org/resources-tools/animal-health-and-welfare/animal-health/pharmacy.
Prescription Requirements
A valid prescription for a non-controlled substance in Illinois must include:
- Name and address of the patient and owner
- Species of the patient
- Date of issue (the date the prescription is prescribed on)
- Name, strength, and quantity of drug or description of the medical device
- Appropriate directions for use
- Prescriber’s name, address, and signature
- Optional:
- Illness, disease, or condition of patient
- Weight
- Intended mg/kg dose
A valid controlled substance prescription must include all the above, plus:
- If written prescription, physical signature in pen or non-editable pencil
- Prescriber’s DEA number (not required on inpatient drug orders)
- For CIIs only: Quantity must be written in both numeric and written form
- Optional: Intended fill date
E.g., to manage refill timing or issue multiple CII prescriptions (e.g., “Do not fill until ___”)
Prescription Changes and Restrictions
After a prescription has been issued, certain elements cannot be altered, even after consultation with a pharmacist.
CIII–CV: The following cannot be changed:
- Patient name
- Medication name
- Prescriber signature
CII: The following cannot be changed:
- Patient name
- Drug identity or formulation (e.g., IR to XR, chewable to non-chewable)
- Prescriber name or addition of signature
- Date of issue or addition of a date
Please note, although changes to non-controlled and CIII–V prescriptions may be called in, the proper procedure is to void the incorrect prescription and rewrite a new, corrected version for accuracy and compliance.
Comparing Prescription Classes
| Class | How long is it good for? | Number of refills allowed | Can it be transferred? | How can the prescription be sent? |
|---|---|---|---|---|
| Legend (non-controlled) | 15 months | Unlimited | Yes, as many times as the patient requires | Written, verbal, faxed†, and electronic |
| CIII-V | 6 months | 5 refills | Once* | Written, verbal, faxed†, and electronic |
| CII | 3 months | None | Once# | Electronic‡ |
| * = If both participating pharmacies share a real-time, online computerized system, the prescription may be transferred up to the maximum number of authorized refills | † = Prescription must still be written, manually signed, and faxed by the prescribers office; this cannot be done by the patient | # = This is effective in Illinois as of June 28, 2024, some institutions may impose stricter internal policies. | ‡ = If a prescriber issues fewer than 150 controlled substance prescriptions per 12-month period (or fewer than 50 beginning January 1, 2029), an electronic prescription is not required and the prescription may be written instead. | |
Emergency Fill
Under Illinois law, veterinarians may prescribe and dispense emergency refills under limited conditions in the absence of a traditional veterinarian-client-patient relationship:
- Up to a 5-day supply of a non-controlled substance medication
- Up to a 3-day supply of a controlled substance medication
Criteria for emergency dispensing (one must apply):
- The patient has a condition that could worsen if treatment is interrupted
- The original prescriber is unavailable to authorize a refill in a timely manner
- The client can show a legitimate need through medical records, a current prescription vial, or contact information for the prescriber
Please note, per Illinois law, the prescribing veterinarian must notify the original prescriber of the emergency fill and can only provide one emergency fill per year. Information regarding the University of Illinois after-hours and weekend medication refill policy is available here.
Compliance with prescription regulations is essential for maintaining safe and ethical veterinary practice. Adhering to Illinois pharmacy laws promotes the appropriate use of medication, protects animal welfare, and preserves the integrity of the veterinary profession. Effective collaboration between pharmacists and veterinarians enhances patient safety, reduces the risk of medication errors, and fosters client trust. As regulations evolve, ongoing education and awareness are necessary to ensure high-quality, legally compliant care across Illinois.
By Denise Colbrook, a fourth-year pharmacy student at the University of Illinois-Chicago.
References
- Illinois Pharmacy Practice Act. 225 ILCS § 85. Accessed November 1, 2025.
- Illinois Pharmacy Practice Act. Transfer of Prescription § 1330.720. Accessed November 1, 2025.
- Illinois Veterinary Medicine and Surgery Practice Act of 2004. 225 ILCS § 115. Accessed November 1, 2025.
- Illinois Controlled Substance Act. 720 ILCS § 570. Accessed November 1, 2025.
- Illinois Controlled Substances Act. 77 ILCS § 3100. Accessed November 1, 2025.
- Pharmacy and prescription issues. American Veterinary Medical Association. Accessed November 1, 2025.
