Hypervitaminosis A in Cats (Felis) | Vetlexicon
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Hypervitaminosis A

ISSN 2398-2950


  • Vitamin A toxicity.
  • Cause: diet high in vitamin A, due to feeding high proportion of diet as liver or excessive supplementation.
  • Signs: anorexia, weight loss, lethargy, neck stiffness, lameness, progressive ankylosis   →   characteristic 'kangaroo' stance.
  • Diagnosis: radiology demonstrating cervical ankylosis and subperiosteal new bone; serology.
  • Treatment: provide diet balanced in vitamin A; supportive.
  • Prognosis: depends on degree of exostosis and ankylosis.
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Presenting signs

  • Anorexia, temperament change.
  • Cervical spondylosis.
  • Neck stiffness.
  • Lameness.
  • Poor grooming.
  • Kittens may have loose or lost teeth.

Age predisposition

  • Naturally occurring - 2-9 years (experimentally induced in kittens).



  • Diet exclusive, or high in, liver.
  • Supplementation with vitamin A.
  • Dietary intake exceeding 60,000 IU/kg bodyweight/day (normal dietary allowance 300 IU/ kg bodyweight).


  • Liver diet.
  • Vitamin A supplementation.


  • Excess dietary vitamin A   →   formation of bony exostoses around joints.
  • Cervical vertebrae (particularly), elbow, hip and stifle joints affected.


  • Months.


Presenting problems

  • Lameness.
  • Anorexia.

Client history

  • Diet.
  • Progressive lameness and stiffness in neck.
  • Weight loss.
  • Crouching gait.

Clinical signs

  • Forelimb lameness.
  • Inability to flex neck.
  • Palpable exostoses in cervical vertebrae.
  • Enlargement of long bones, sternebrae and ribs.
  • Cutaneous hyperesthesia.
  • Shortening of long bones in kittens.

Diagnostic investigation


  • Cervical ankylosis  Bone: hypervitaminosis A - spine  and spondylosis.
  • Subperiosteal new bone deposition.
  • Joint enlargement and remodelling.
  • Limb joint exostoses, especially shoulder and elbow.


  • ?Vitamin A 451-1281 ucg/dl.

Confirmation of diagnosis

Discriminatory diagnostic features

  • Signs.
  • History.

Definitive diagnostic features

  • Radiology.


Standard treatment

  • Restore balanced diet - remove source of excessive vitamin A.
  • Provide supportive therapy - elevate feed bowls so cat can eat more easily.
  • Musculoskeletal anti-inflammatories Therapeutics: musculoskeletal system.



  • Feed diet balanced in vitamin A.



  • Fair - if early in disease, restoration of balanced diet will halt progress.
  • Guarded - if ankylosis advanced.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Polizopoulou Z S, Kazakos G, Patsikas M N et al (2005) Hypervitaminosis A in the cat: a case report and review of the literature. J Feline Med Surg (6), 363-368 PubMed.
  • Coates J W (1998) Measuring vitamin A in blood plasma and serum. Can Vet J 39 (5), 261 PubMed.

Other sources of information

  • Holzworth J (1987) Diseases of the Cat. In: Medicine and Surgery. W B Saunders.