What is a Clinical Vitamin A Deficiency? Understanding the Causes, Symptoms, and Impact

December 16, 2025 •

3 min read

Globally, vitamin A deficiency (VAD) is the leading cause of preventable childhood blindness, with an estimated 250,000 to 500,000 children becoming blind each year due to this condition. Clinical vitamin A deficiency occurs when the body's vitamin A reserves are critically low, leading to distinct, often severe, health problems. This critical nutrient is vital for vision, immune function, reproduction, and cell growth.

Quick Summary

Clinical vitamin A deficiency is a serious nutritional disorder resulting in inadequate vitamin A levels. It causes vision problems, skin issues, and weakened immune function, particularly in children and pregnant women.

Key Points

Ocular Symptoms: Night blindness is often the first symptom, followed by severe dry eyes (xerophthalmia), Bitot's spots, and potentially corneal destruction (keratomalacia).
Underlying Causes: Deficiency can stem from inadequate diet, fat malabsorption disorders (like cystic fibrosis), or liver disease affecting storage.
Diagnosis is Primarily Clinical: While blood tests exist, diagnosis relies heavily on observable signs and symptoms, especially in resource-limited settings.
Reversible but with Limits: Early symptoms like night blindness are reversible with management, but corneal scarring from advanced deficiency can cause permanent blindness.
Prevention is Key: Effective prevention involves a balanced diet rich in vitamin A, fortified foods, and targeted programs for high-risk populations.

What is clinical vitamin A deficiency?

Clinical vitamin A deficiency (VAD) is a severe condition characterized by low serum retinol levels and depleted body stores of vitamin A. The clinical stage manifests with observable symptoms, primarily affecting the eyes. Vitamin A is an essential nutrient that the body cannot produce and must be obtained from diet or supplements. Severe deficiency is indicated by serum retinol levels below 0.35 µmol/L.

Causes of clinical VAD

Clinical VAD stems from either insufficient dietary intake or problems with the body's handling of vitamin A.

Dietary insufficiency: A lack of vitamin A-rich foods in the diet is a major cause in many regions.
Fat malabsorption: Conditions like cystic fibrosis, chronic diarrhea, celiac disease, and certain surgeries hinder the absorption of fat-soluble vitamin A.
Liver disorders: Liver diseases, such as cirrhosis, impair the liver's ability to store vitamin A.
Increased demand: Groups like young children and pregnant or breastfeeding women have higher needs, increasing their risk.
Infections: Illnesses, particularly measles and diarrhea, can deplete vitamin A reserves.

Symptoms and clinical manifestations

Symptoms are categorized as ocular (eye-related) and non-ocular, with ocular signs known collectively as xerophthalmia.

Ocular signs (Xerophthalmia)

Night Blindness (Nyctalopia): Often the first symptom, causing difficulty seeing in low light.
Conjunctival Xerosis: The membrane covering the eye becomes dry and thickened.
Bitot's Spots: Foamy, whitish-gray patches appear on the conjunctiva.
Corneal Xerosis: The cornea becomes dry and hazy.
Keratomalacia: Severe dryness leads to corneal softening, ulceration, and potential irreversible blindness.

Non-ocular signs

Dry, scaly skin (Phrynoderma): Skin becomes dry and rough, with potential follicular hyperkeratosis.
Impaired immunity: Weakens the immune system, increasing susceptibility to infections.
Delayed growth: Can stunt growth in children.
Reproductive issues: Can contribute to infertility.

Diagnosis of clinical VAD

Diagnosis is primarily clinical, based on patient history and physical examination, especially of the eyes and skin. While serum retinol levels can be measured, they may only be low in advanced stages due to liver stores. An empirical trial with vitamin A supplements can also be diagnostic. Specialized tests for impaired dark adaptation may be used.

Comparison of ocular vitamin A deficiency stages


Stage	Key Clinical Sign	Characteristic Description	Reversibility	Public Health Significance
Night Blindness (XN)	Impaired dark adaptation	Difficulty seeing in low light; earliest sign.	Fully reversible.	Indicates a mild to moderate problem in populations.
Bitot's Spots (X1B)	Foamy patches on conjunctiva	Keratinized growths on the conjunctiva.	Reversible, though spots may persist.	Indicates a moderate to severe problem in populations.
Corneal Xerosis (X2)	Dry, hazy cornea	Drying and thickening of the cornea.	Partially or fully reversible.	Indicates a severe public health problem.
Keratomalacia (X3A/B)	Corneal ulcers/softening	Ulceration and softening of the cornea.	May lead to irreversible blindness.	Indicates a severe public health problem with high mortality.

Management and prevention

Management involves addressing the deficiency with appropriate strategies. These strategies can reverse night blindness and dry eyes, but may not restore vision if corneal scarring has occurred. Prevention involves dietary diversification, food fortification, and programs aimed at addressing deficiency in at-risk populations. The World Health Organization website offers more information on global efforts.

What are the key distinctions between subclinical and clinical vitamin A deficiency?

Subclinical VAD: Low serum retinol levels without visible clinical signs. Clinical VAD: Severe deficiency presenting with overt symptoms like night blindness and xerophthalmia.

Frequently Asked Questions

The earliest and most specific symptom is night blindness (nyctalopia), which is the difficulty seeing in dim light or adapting to darkness.

Yes, vitamin A deficiency can be subclinical, where blood levels are low but visible signs are absent, or clinical, where visible symptoms like xerophthalmia and other severe issues are present.

Management involves strategies to address the deficiency, often through nutritional approaches recommended by healthcare professionals, with dosages adjusted based on individual needs and severity.

Blindness can be prevented and early visual symptoms like night blindness can be reversed with management. However, blindness caused by corneal scarring from advanced keratomalacia is irreversible.

Foods rich in vitamin A include animal liver, dairy products, eggs, and oily fish. Plant-based sources containing beta-carotene include carrots, sweet potatoes, spinach, and other dark green or orange vegetables.

Young children, pregnant women, and lactating women, particularly those living in low-income countries or with fat malabsorption disorders, are most vulnerable.

Bitot's spots are pathognomonic signs of VAD appearing as foamy, whitish-gray patches of keratinized epithelial cells on the conjunctiva, indicating advanced deficiency.