A number of functions for vitamin A have been found, including defense mechanisms, maintenance of healthy epithelial tissues, and most importantly, a function in the visual system.  A deficiency may manifest itself by: 1.) A scale-like appearance in the skin and occasional acne, 2.) A failure of growth in young animals, including C. station of skeletal growth, and 3.) A failure of reproduction associated with atrophy of the epithelial cells of the testes and interruption of the female sexual cycle.  A deficiency may also represent a decreased visual acuity, and more specifically, night blindness. This was found in a patient who complained that they were unable to read a particular sign at night while driving, but was able to read it during the day

When a patient is diagnosed with a deficiency, the treatment will require aggressive oral supplementation. For cases in which vitamin A levels do not respond to “Dry” Vitamin A oral supplementation, intramuscular injections may be required. The usual injected dosage is between 25,000-50,000 international units. Repeated injections in a 3-month interval have been required in some patients to normalize their level, as well as resolving the symptom of night blindness.