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Levothyroxine

Detailed information about Levothyroxine

Official label facts Owner quick guide first Marketing clearly labeled
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Reviewed / Updated / Sources

Reviewed: Not available

Updated: February 12, 2026, 10:44 PM UTC

Sources:

Pet Owner Quick Guide

Start here first for the simple next-step summary.

Used for:

For replacement therapy for diminished thyroid function in dogs.

What to watch for:

  • For oral use in dogs only
  • Stroke (1 reports)
  • Proteinuria (1 reports)
  • Partial lack of efficacy (1 reports)

When to call the vet:

  • Repeated vomiting or diarrhea.
  • Severe lethargy (hard to wake, very low energy).
  • Collapse or fainting.
  • Trouble breathing.
  • Facial swelling or hives.
  • Blood in vomit or stool.

Regulatory restrictions are shown in Vet View.

What to ask your vet today:

  • Is this medicine the right fit for my pet’s current symptoms?
  • Which warning signs mean I should call back right away?
  • How should I handle missed doses or refusal to take the medicine?
Safety & side effects

What to watch:

  • For oral use in dogs only
  • Stroke
  • Proteinuria
  • Partial lack of efficacy

Most reported reactions:

  • Stroke (1 reports)
  • Proteinuria (1 reports)
  • Partial lack of efficacy (1 reports)

When to call your vet:

  • Repeated vomiting or diarrhea.
  • Severe lethargy (hard to wake, very low energy).
  • Collapse or fainting.
  • Trouble breathing.
Talk to a Vet / Find a Vet Near You Start Symptom Intake

Data freshness: source data appears current.

Latest refresh: Mar 21, 2026, 10:01 a.m.

Data freshness
  • Medication catalog: Source Roxee | Refreshed Feb 12, 2026, 10:44 PM UTC
  • Animal Drugs @ FDA: Source FDA | Refreshed Mar 21, 2026, 10:00 AM UTC
    Applications/products are imported from FDA export data.
  • Animal Drugs @ FDA previews: Source FDA | Refreshed Feb 9, 2026, 3:05 AM UTC
    Label highlights/doc links are fetched from FDA preview endpoints.
  • Animal Drug Product Listing Directory (NDC): Source FDA | Refreshed Mar 21, 2026, 10:01 AM UTC
    Package/product NDCs from FDA’s electronic listing directory (XLS).
  • openFDA reaction terms: Source FDA openFDA | Refreshed Mar 15, 2026, 10:04 AM UTC
  • openFDA case summaries: Source FDA openFDA | Refreshed Feb 9, 2026, 3:21 AM UTC
Image coming soon
Levothyroxine

Levothyroxine

Drug type: Generic ingredient • Branded profile • FDA branded products available

Species: Both

Manufacturer: Not available (source)

Quick Facts

Official label facts first, then secondary summaries. Marketing content is separated below.

Species: Both
Manufacturer: Not available
Form: Tablet
Identifiers:
NADA: 141448 NADA: 141539 NDC Package: 11695-6957-1 NDC Package: 11695-6957-2 NDC Package: 11695-6958-1 NDC Package: 11695-6958-2 NDC Package: 11695-6959-1 NDC Package: 11695-6959-2 NDC Package: 11695-6960-1 NDC Package: 11695-6960-2 NDC Package: 11695-6961-1 NDC Package: 11695-6961-2 NDC Package: 11695-6962-1 NDC Package: 11695-6962-2 NDC Package: 11695-6963-1 NDC Package: 11695-6963-2 NDC Package: 11695-6964-1 NDC Package: 11695-6964-2 NDC Package: 11695-6965-1 NDC Package: 11695-6965-2
Source metadata:

Warnings / Contraindications

For oral use in dogs only. Federal law restricts this drug to use by or on the order of a licensed veterinarian.

  • High: For oral use in dogs only. Federal law restricts this drug to use by or on the order of a licensed veterinarian.
Source metadata:

Adverse Reactions

Snapshot first, detailed rows second. This section summarizes signal data and is not a diagnosis.

Tap or hover a reaction to see what it means in plain language.

Tracked signals
32
Reported cases
32
Serious reports
19
Species represented
2
Grouped by Body System
Digestive (3) · Loss of appetite, Diarrhea, Bloody diarrhoea Neurologic (1) · Tiredness (lethargy) Effectiveness (2) · Partial lack of efficacy, Lack of efficacy - NOS Other (26) · Stroke, Shaking, Regenerative anaemia
Most Reported Reactions
Reaction Body system Cases Species Serious cases
Other 1 Cat 1
Other 1 Cat 1
Effectiveness 1 Cat 1
Other 1 Dog 1
Digestive 1 Dog 1
Other 1 Dog 1
Other 1 Cat 1
Other 1 Cat 1

Species coverage: Dog (18) Cat (14)

View detailed reaction table
Reaction Body system Species Seriousness Frequency Reports
Neurologic Dog Non-serious - 1
Other Cat Serious - 1
Other Dog Non-serious - 1
Other Dog Non-serious - 1
Other Cat Serious - 1
Other Cat Non-serious - 1
Effectiveness Cat Serious - 1
Other Dog Serious - 1
Other Cat Non-serious - 1
Other Dog Non-serious - 1
Digestive Dog Serious - 1
Other Dog Non-serious - 1
Other Dog Non-serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Effectiveness Dog Non-serious - 1
Other Dog Non-serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Other Cat Serious - 1
Digestive Dog Non-serious - 1
Other Cat Serious - 1
Other Dog Non-serious - 1
Digestive Dog Non-serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Other Dog Serious - 1
Other Cat Serious - 1
Source metadata:

Documents

Owner handouts and official technical documents are grouped for faster access.

Owner handouts (0)
  • No owner handouts linked yet.
Official label / PI (0)
  • No official label or package insert links yet.
SPL (2)
  • ThyroKare™ · SPL
    https://animaldrugsatfda.fda.gov/adafda/app/search/public/spl/file/10370/ThyroKare%E2%84%A2
  • Thyro-Tabs® Canine · SPL
    https://animaldrugsatfda.fda.gov/adafda/app/search/public/spl/file/2392/Thyro-Tabs%C2%AE%20Canine
FOI (2)
Source metadata:
Veterinary reference (advanced)

Canonical medication sections are above. This legacy block remains available for deeper cross-reference without cluttering the primary workflow.

At a Glance

Quick facts and links to official labeling and safety signals.

Data freshness
  • Medication catalog: Source Roxee | Refreshed Feb 12, 2026, 10:44 PM UTC
  • Animal Drugs @ FDA: Source FDA | Refreshed Mar 21, 2026, 10:00 AM UTC
    Applications/products are imported from FDA export data.
  • Animal Drugs @ FDA previews: Source FDA | Refreshed Feb 9, 2026, 3:05 AM UTC
    Label highlights/doc links are fetched from FDA preview endpoints.
  • Animal Drug Product Listing Directory (NDC): Source FDA | Refreshed Mar 21, 2026, 10:01 AM UTC
    Package/product NDCs from FDA’s electronic listing directory (XLS).
  • openFDA reaction terms: Source FDA openFDA | Refreshed Mar 15, 2026, 10:04 AM UTC
  • openFDA case summaries: Source FDA openFDA | Refreshed Feb 9, 2026, 3:21 AM UTC
Official (FDA)
Identity: Generic ingredient • FDA branded products available
Official FDA brands: Thyro-Tabs® Canine ThyroKare™
Case-reported brands (openFDA): MSK
Catalog species: Both • FDA-labeled species: Dog
Rx/OTC: RX
Form/route: Tablet • Oral
Applications: NADA 141-539 • NADA 141-448
Documents: 2 (FOI: 2) • SPL: 2 • Label highlights • Official documents
Safety (openFDA)
Top reactions: Dog 25 • Cat 8 • View
Case summaries: 10 (showing 8) • View
openFDA reports are unverified and do not prove causation.
Diagnosis Codes

Diagnosis-code mappings are not available for this medication yet.

Counseling and Monitoring Highlights

Global Pet owner/Vet mode is controlled in the header. This section avoids duplicate in-page persona tabs.

Owner-facing counseling points
  • For oral use in dogs only. Federal law restricts this drug to use by or on the order of a licensed veterinarian. (Contraindication, High)
Top reaction signals
Stroke (1) Proteinuria (1) Partial lack of efficacy (1) Pancytopenia (1) Loss of appetite (1) Leucopenia NOS (1) Lameness (1) Hyperphosphataemia (1)

Identifiers & Packages

Normalized identifiers (NDC/NADA/ANADA) and package metadata from regulator listings.

Identifiers
NADA: 141448 NADA: 141539 NDC Package: 11695-6957-1 NDC Package: 11695-6957-2 NDC Package: 11695-6958-1 NDC Package: 11695-6958-2 NDC Package: 11695-6959-1 NDC Package: 11695-6959-2 NDC Package: 11695-6960-1 NDC Package: 11695-6960-2 NDC Package: 11695-6961-1 NDC Package: 11695-6961-2 NDC Package: 11695-6962-1 NDC Package: 11695-6962-2 NDC Package: 11695-6963-1 NDC Package: 11695-6963-2 NDC Package: 11695-6964-1 NDC Package: 11695-6964-2 NDC Package: 11695-6965-1 NDC Package: 11695-6965-2 NDC Package: 11695-7014-1 NDC Package: 11695-7014-2 NDC Package: 11789-048-10 NDC Package: 11789-048-20
Package NDC Product NDC Form / Route Status
11695-6957-1 11695 -
11695-6957-2 11695 -
11695-6958-1 11695 -
11695-6958-2 11695 -
11695-6959-1 11695 -
11695-6959-2 11695 -
11695-6960-1 11695 -
11695-6960-2 11695 -
11695-6961-1 11695 -
11695-6961-2 11695 -
11695-6962-1 11695 -
11695-6962-2 11695 -
11695-6963-1 11695 -
11695-6963-2 11695 -
11695-6964-1 11695 -
11695-6964-2 11695 -
11695-6965-1 11695 -
11695-6965-2 11695 -
11695-7014-1 11695 -
11695-7014-2 11695 -

Enriched Documents

Documents are tiered by source trust: Official, Clinical, Manufacturer, Marketing.

Data Sources & Change Log

Every non-trivial field is expected to include provenance and update timestamps.

Official 5 Clinical 0 Manufacturer 0 Marketing 0
Current Field Facts
  • contraindications: For oral use in dogs only. Federal law restricts this drug to use by or on the order of a licensed veterinarian. (Official, 2026-02-12)
  • side_effects: Top reported reactions (openFDA): Vomiting, Diarrhoea, Lethargy (see also Central nervous system depression in 'Neurological'), Death by euthanasia, Lack of ef… (Official, 2026-02-12)
  • usage: For replacement therapy for diminished thyroid function in dogs. (Official, 2026-02-12)
Recent Revisions
  • side_effects updated 2026-02-12 22:44 by etl_backfill • Backfilled from existing medication fields
  • contraindications updated 2026-02-12 22:44 by etl_backfill • Backfilled from existing medication fields
  • usage updated 2026-02-12 22:44 by etl_backfill • Backfilled from existing medication fields

FDA Products & Applications (Animal Drugs @ FDA)

Official sponsor/proprietary-name/application-status records linked by active ingredient.

Product Sponsor Application Status Published
ThyroKare™
RX
Levothyroxine sodium
Tablet • Oral
Label highlights
Official documents
Neogen Corp. NADA 141-539 Approved Feb 1, 2021
Thyro-Tabs® Canine
RX
Levothyroxine sodium
Tablet • Oral
Label highlights
Official documents
Lloyd, Inc. NADA 141-448 Approved Jun 1, 2016

Data source: FDA Animal Drugs @ FDA (public search export).

What It's For (FDA Label Highlights)

Extracted from FDA Animal Drugs @ FDA product labeling. Always confirm details with your veterinarian.

Species: Dog, No Use Class Stated Or Implied
Composition / specifications
0.1 mg, 0.2 mg, 0.3 mg, 0.4 mg, 0.5 mg, 0.6 mg, 0.7 mg, 0.8 mg, or 1.0 mg of levothyroxine sodium per tablet
Dogs
Indication

For replacement therapy for diminished thyroid function in dogs.

Dosage

The initial dose is 0.1 mg/10 lb (0.01 mg/lb, 0.022 mg/kg) body weight twice daily.

Limitations

FDA page: Open in Animal Drugs @ FDA

Species: Dog, No Use Class Stated Or Implied
Composition / specifications
0.1 mg, 0.2 mg, 0.3 mg, 0.4 mg, 0.5 mg, 0.6 mg, 0.7 mg, 0.8 mg, or 1.0 mg of levothyroxine sodium per tablet
Dogs
Indication
For replacement therapy for diminished thyroid function in dogs.
Dosage
Administer by mouth 0.1 mg/10 pounds of body weight (0.022 mg/kilogram) as a single dose every 24 hours or as a divided dose every 12 hours.
Limitations
For oral use in dogs only. Federal law restricts this drug to use by or on the order of a licensed veterinarian.

FDA page: Open in Animal Drugs @ FDA

Official Documents (FDA)

Direct links to FDA-hosted PDFs and SPL packages (when available).

Documents
SPL Packages

FDA page: Open in Animal Drugs @ FDA

Documents
  • Summary
    For replacement therapy for diminished thyroid function in dogs.
SPL Packages

FDA page: Open in Animal Drugs @ FDA

Usage

For replacement therapy for diminished thyroid function in dogs.

Source: FDA Animal Drugs @ FDA • Reference

Contraindications

For oral use in dogs only. Federal law restricts this drug to use by or on the order of a licensed veterinarian.

Top Reported Reactions (openFDA)

De-duplicated reaction terms grouped by body system from FDA openFDA reports (not verified; does not prove causation).

Digestive
Loss of appetite (1) • Dog Diarrhea (1) • Dog Bloody diarrhoea (1) • Dog

Showing top 5 for Digestive.

Neurologic
Tiredness (1) • Dog

Showing top 5 for Neurologic.

Effectiveness
Partial lack of efficacy (1) • Cat Lack of efficacy - NOS (1) • Dog

Showing top 5 for Effectiveness.

Other
Stroke (1) • Cat Shaking (1) • Dog Regenerative anaemia (1) • Dog Proteinuria (1) • Cat Product compounding error (1) • Cat
Show more (21)
Pancytopenia (1) • Dog No sign (1) • Cat Low thyroxine (1) • Dog Localised oedema (1) • Dog Lick granuloma (1) • Dog Leucopenia NOS (1) • Dog Lameness (1) • Cat Hypothyroidism (1) • Dog Hyperphosphataemia (1) • Cat Hepatomegaly (1) • Dog Gastric ulcer (1) • Dog Gait abnormality (1) • Cat Elevated symmetrical dimethylarginine (1) • Cat Elevated creatinine (1) • Cat Decreased urine concentration (1) • Cat Cellulitis (1) • Dog Blood in urine (1) • Cat Blood in faeces (1) • Dog Blindness (1) • Cat Anaemia NOS (1) • Dog Acute renal failure (1) • Cat

Showing top 5 for Other.

Data source: FDA openFDA Animal & Veterinary adverse event reports.

Adverse Event Case Summaries (openFDA)

These are individual FDA adverse event reports. They are unverified and do not prove the medication caused the reaction.

Dog, Mastiff (unspecified), Male, 5.5 year, 90.26 kilogram • Drug: MSK, Unknown • Reactions: Regenerative anaemia, Tiredness (lethargy), Localised oedema, Uncomfortable, Lack of efficacy - NOS… • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2025-US-054417
  • Serious AE: No
  • Treated For AE: Yes
  • Sex: Male
  • Age: 5.50 Year
  • Weight: 90.260 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
Reactions Reported:
Regenerative anaemia Tiredness (lethargy) Localised oedema Uncomfortable Lack of efficacy - NOS Cellulitis Low thyroxine Swelling NOS Hypothyroidism Lick granuloma
Outcomes: Ongoing

Dog, Chihuahua, Female, 12 year, 8.16 kilogram • Drug: MSK, Unknown • Reactions: Tarry or black stool • Outcome: Recovered/Normal

  • Report ID: USA-USFDACVM-2025-US-054372
  • Serious AE: No
  • Treated For AE: No
  • Sex: Female
  • Age: 12.00 Year
  • Weight: 8.160 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
Reactions Reported:
Tarry or black stool
Outcomes: Recovered/Normal

Dog, Terrier - Jack Russell, Male, 12 year, 8.5 kilogram • Drug: MSK, Tablet, Oral • Reactions: Leucopenia NOS, Loss of appetite, Anaemia NOS, Pancytopenia, Hepatomegaly… • Outcome: Outcome Unknown

  • Report ID: USA-USFDACVM-2025-US-055620
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Male
  • Age: 12.00 Year
  • Weight: 8.500 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Oral
  • Form: Tablet
Reactions Reported:
Leucopenia NOS Loss of appetite Anaemia NOS Pancytopenia Hepatomegaly Blood in faeces Gastric ulcer Weight loss Unwell White blood cell disorder NOS
Outcomes: Outcome Unknown

Dog, ['Retriever - Labrador', 'Poodle (unspecified)'], Male, 4 year, 27.44 kilogram • Drug: MSK, Unknown • Reactions: Wobbliness, Shaking • Outcome: Outcome Unknown

  • Report ID: USA-USFDACVM-2025-US-054472
  • Serious AE: No
  • Treated For AE: No
  • Sex: Male
  • Age: 4.00 Year
  • Weight: 27.440 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
Reactions Reported:
Wobbliness Shaking
Outcomes: Outcome Unknown

Dog, Terrier - American Staffordshire, Male, 12 year, 33.11 kilogram • Drug: MSK, Unknown • Reactions: Diarrhea, Bloody diarrhoea • Outcome: Recovered/Normal

  • Report ID: USA-USFDACVM-2025-US-053304
  • Serious AE: No
  • Treated For AE: Yes
  • Sex: Male
  • Age: 12.00 Year
  • Weight: 33.110 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
Reactions Reported:
Diarrhea Bloody diarrhoea
Outcomes: Recovered/Normal

Cat, Cat (unknown), Female, 15 year, 3.57 kilogram • Drug: MSK, Tablet, Oral • Reactions: Vomiting, Acute renal failure, Elevated symmetrical dimethylarginine, Elevated creatinine, Decreased urine concentration… • Outcome: Outcome Unknown

  • Report ID: USA-USFDACVM-2025-US-034962
  • Serious AE: Yes
  • Treated For AE: No
  • Sex: Female
  • Age: 15.00 Year
  • Weight: 3.570 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Oral
  • Form: Tablet
Reactions Reported:
Vomiting Acute renal failure Elevated symmetrical dimethylarginine Elevated creatinine Decreased urine concentration Blood in urine Proteinuria Hyperphosphataemia
Outcomes: Outcome Unknown

Cat, Domestic Longhair, Female, 15 year, 3.57 kilogram • Drug: MSK, Unassigned, Unknown • Reactions: Vomiting, Acute renal failure, Elevated symmetrical dimethylarginine, Elevated creatinine, Decreased urine concentration… • Outcome: Ongoing

  • Report ID: USA-USFDACVM-2025-US-026652
  • Serious AE: Yes
  • Treated For AE: Yes
  • Sex: Female
  • Age: 15.00 Year
  • Weight: 3.570 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
  • Form: Unassigned
Reactions Reported:
Vomiting Acute renal failure Elevated symmetrical dimethylarginine Elevated creatinine Decreased urine concentration Blood in urine Proteinuria Hyperphosphataemia
Outcomes: Ongoing

Cat, Domestic Shorthair, Male, 16 year, 4.62 kilogram • Drug: MSK, Unknown • Reactions: No sign, Product compounding error

  • Report ID: USA-USFDACVM-2025-US-025802
  • Serious AE: No
  • Treated For AE: No
  • Sex: Male
  • Age: 16.00 Year
  • Weight: 4.620 Kilogram
  • Case-reported brand: MSK
  • Case-reported manufacturer: MSK
  • Route: Unknown
Reactions Reported:
No sign Product compounding error

Data source: FDA openFDA Animal & Veterinary adverse event reports.

Overdose Information

No approved overdose-management text is linked yet. If overdose is suspected, contact a veterinarian or emergency clinic immediately.

Storage & Handling

No approved storage guidance is linked yet for this ingredient. Use manufacturer packaging and veterinary guidance for handling/storage.

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