21 CFR § 520.1248 - Levothyroxine.

---
identifier: "/us/cfr/t21/s520.1248"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 520.1248 - Levothyroxine."
title_number: 21
title_name: "Food and Drugs"
section_number: "520.1248"
section_name: "Levothyroxine."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "E"
subchapter_name: "ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS"
part_number: "520"
part_name: "ORAL DOSAGE FORM NEW ANIMAL DRUGS"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "21 U.S.C. 360b."
regulatory_source: "40 FR 13838, Mar. 27, 1975, unless otherwise noted."
cfr_part: "520"
---


# 520.1248 Levothyroxine.

(a) *Specifications.* Each tablet contains 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 1.0 milligrams (mg) levothyroxine sodium.

(b) *Sponsors.* See Nos. 059051 and 061690 in § 510.600(c) of this chapter.

(c) *Conditions of use*—(1) *Amount.* Administer by mouth as follows:

(i) No. 061690: 0.1 mg/10 pounds (lb) body weight (0.022 mg/kilogram (kg)) as a single dose every 24 hours or as a divided dose every 12 hours.

(ii) No. 059051: 0.1 mg/10 lb (0.01 mg/lb, 0.022 mg/kg) body weight twice daily.

(2) *Indications for use.* For replacement therapy for diminished thyroid function in dogs.

(3) *Limitations.* Federal law restricts this drug to use by or on the order of a licensed veterinarian.

[81 FR 22523, Apr. 18, 2016, as amended at 86 FR 57996, Oct. 20, 2021]