Vitamin A
Vitaminas y mineralesÚltima revisión: 7 de abril de 2026. Enfoque de fuentes: contexto estándar de interpretación de laboratorio, material médico de referencia y orientación clínica o de salud pública cuando corresponde.
¿Qué es Vitamin A?
Vitamin A is a fat-soluble vitamin essential for vision, immune function, reproduction, and cellular communication. It exists in two principal forms: preformed vitamin A (retinol and retinyl esters), found in animal products such as liver, dairy, and fish, and provitamin A carotenoids (most notably beta-carotene), found in colorful fruits and vegetables. Retinol is the most biologically active form and is the primary circulating form measured in blood tests.
After absorption in the small intestine, vitamin A is stored primarily in the liver as retinyl esters—the liver stores approximately 80–90% of the body's total vitamin A. Serum retinol levels are tightly regulated by the liver and remain stable until stores are significantly depleted or excessively accumulated. This homeostatic control means that blood levels may not reflect total body stores until deficiency or toxicity is advanced. Vitamin A is critical for maintaining the integrity of epithelial tissues, supporting the differentiation of immune cells, and enabling the retinal pigment rhodopsin to function in low-light vision.
Por qué importa
Vitamin A deficiency is the leading cause of preventable blindness in children worldwide and significantly impairs immune function, increasing susceptibility to infections and mortality from measles and diarrheal diseases. Conversely, because vitamin A is fat-soluble and stored in the liver, excessive intake—particularly from supplements or liver consumption—can cause hypervitaminosis A, leading to liver damage, bone loss, birth defects, and neurological symptoms. Maintaining appropriate vitamin A levels supports healthy vision, robust immunity, and normal fetal development.
Rangos de referencia normales
| Grupo | Rango | Unidad |
|---|---|---|
| Adults | 30–65 | mcg/dL |
| Children (1–6 years) | 20–43 | mcg/dL |
| Children (7–12 years) | 26–49 | mcg/dL |
Los rangos de referencia pueden variar entre laboratorios. Compara siempre tus resultados con los rangos proporcionados por tu laboratorio.
Qué significan los niveles altos de Vit A
Causas comunes
- Excessive vitamin A supplementation
- Chronic consumption of liver or liver products
- Accutane (isotretinoin) or other retinoid medications
- Kidney disease (impaired excretion)
- Hyperlipidemia (increased carrier proteins)
Posibles síntomas
- Nausea, vomiting, and abdominal pain
- Headaches and blurred vision
- Dry, peeling skin and lip cracking
- Bone and joint pain
- Hair loss
- Liver enlargement and damage
- Birth defects if taken during pregnancy
Qué hacer: Stop all vitamin A supplements and limit dietary sources of preformed vitamin A. Seek medical evaluation for liver function testing. Acute toxicity from a single massive dose is a medical emergency. Chronic toxicity typically resolves within weeks to months after discontinuation but may require monitoring for liver damage. Women who are pregnant or planning pregnancy should avoid retinoid medications and high-dose vitamin A supplements.
Qué significan los niveles bajos de Vit A
Causas comunes
- Inadequate dietary intake
- Fat malabsorption (celiac disease, Crohn's disease, cystic fibrosis)
- Liver disease (impaired storage and release)
- Zinc deficiency (zinc is needed to transport vitamin A)
- Chronic alcoholism
- Pancreatic insufficiency
Posibles síntomas
- Night blindness (nyctalopia)—earliest symptom
- Dry eyes (xerophthalmia) and corneal damage
- Dry, rough skin and poor wound healing
- Increased susceptibility to infections
- Growth retardation in children
- Bitot's spots (white patches on the conjunctiva)
Qué hacer: Mild deficiency is treated with dietary improvement—increasing intake of liver, eggs, dairy, sweet potatoes, carrots, and dark leafy greens. Moderate to severe deficiency requires supplementation under medical supervision, typically with retinyl palmitate. Underlying malabsorption issues should be addressed. In developing countries, high-dose vitamin A supplementation programs have significantly reduced childhood mortality.
¿Cuándo se recomienda la prueba de Vit A?
- When night blindness or vision changes are reported
- In patients with fat malabsorption syndromes
- When liver disease is present
- If vitamin A toxicity is suspected from over-supplementation
- In malnourished populations or children with growth failure
- When taking retinoid medications
Preguntas frecuentes
Biomarcadores relacionados
Referencias y enfoque de revisión
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Subir resultados de laboratorio →Aviso médico: Esta información es solo educativa y no sustituye el consejo, diagnóstico ni tratamiento médico profesional. Los rangos de referencia pueden variar entre laboratorios. Consulta siempre a tu profesional sanitario para interpretar tus resultados concretos.