Do You Need a Vitamin A Deficiency Test? Consider This First

Important Considerations Before a Vitamin A Deficiency Test

• Vitamin A Testing|
• Vitamin A and Its Sources|
• Vitamin A Deficiency Risk Factors|
• Vitamin A Deficiency Symptoms|
• Vitamin A Supplements|
• Vitamin A Toxicity|

Vitamin A deficiency is rare, but if you’re experiencing symptoms such as bumps on the back of your arms, dry eyes, night blindness, and getting sick often, an inexpensive blood test can reliably detect this vitamin deficiency. 

However, serum vitamin A levels remain normal on a test until a severe deficiency occurs, so a vitamin A deficiency test is generally unnecessary if you are healthy and don’t have any of the symptoms of vitamin A deficiency. 

In this article, we’ll break down what you need to know about vitamin A including what it is, possible signs and symptoms of a deficiency, available vitamin A deficiency test options, factors that can affect your vitamin A level, and supplementation.

Vitamin A Testing

A vitamin A deficiency test is unnecessary for most healthy adults and young children for a couple of reasons:

• Vitamin A deficiency is rare in developed countries.
• Unless you are already severely deficient, a serum vitamin A lab test probably won’t give an accurate picture of your vitamin A status because it tests levels in your blood, not your liver. 50%-85% of your vitamin A is stored in the liver. Serum vitamin A levels in healthy people remain pretty constant until liver reserves are severely depleted [1, 2].

However, a vitamin A deficiency test may be helpful  if:

• You are at high risk (I’ll talk about this later)
• You have deficiency symptoms
• Your physician suspects a deficiency

If you need to test your vitamin A levels, a serum (blood) retinol (vitamin A) test is the most reliable and practical test for vitamin A deficiency. This vitamin A deficiency test correlates closely with the prevalence and severity of xerophthalmia (dry eye) and may change with supplementation [3].  

Serum retinol can be assessed by using two different lab methods called  high-performance liquid chromatography (HPLC) and spectrophotometry. The latter is more simple and less expensive, but HPLC is still usually less than 40 dollars, is more accurate, and is the preferred method.

There is generally no need for any other kind of specialized testing, which can be expensive and less accessible. These other tests may include:

• A liver biopsy is the gold standard for vitamin A testing, but this is obviously not practical and not necessary for most people [2].
• Dried blood spot retinol testing, which has been shown to correlate well with serum retinol levels [3, 4].

A serum vitamin A level of 58.3 micrograms per deciliter (mcg/dL) may be optimal. If your level has fallen below 20 mcg/dL, your liver stores are already severely depleted and you will need to begin supplementation as soon as possible under the advice of your health care provider [5].

Vitamin A and Where You Can Find It

Vitamin A refers to a group of compounds. The forms of vitamin A include retinol, retinoic acid, retinal, and provitamin A carotenoids. Vitamin A is important for proper immune function, cell growth and repair, bone growth, reproduction, and normal embryonic and fetal development [6].

Since it can’t be created by the body, vitamin A is an essential nutrient. This means you need to get it through your diet or supplements. There are a variety of plant and animal sources. 

Preformed vitamin A (retinol or retinoic acid) can be found in [3]: 

• Breast milk
• Liver
• Cod liver oil
• Dairy products
•  Egg yolks 

Provitamin A carotenoids (beta-carotene) are found in plant foods [3]:

• Dark green leafy vegetables
• Deeply colored yellow and orange vegetables and fruit

Who Is at Risk of Vitamin A Deficiency?

Vitamin A deficiency is rare in developed countries, but researchers in one study of bariatric (weight loss) surgery patients reported this vitamin deficiency in up to 69% of the study group [7]. Weight loss surgery is designed to induce weight reduction, but in the process can create nutrient malabsorption.

 Other high-risk populations include:  

• Preterm infants
• Infants with vitamin A-deficient mothers
• Those with gastrointestinal malabsorption:
  • Celiac disease (an autoimmune disease where the body reacts strongly to gluten)
  • Short bowel syndrome (poor absorption of nutrients)
  • Exocrine pancreatic insufficiency (lack of adequate digestive enzymes from the pancreas)
  • Crohn’s disease (inflammation in the digestive tract)
• Alcoholics and those with non-alcoholic fatty liver disease
• Those consuming a diet that’s very low in fat 
• Those with malnutrition or inadequate nutrient intake

What Are the Signs and Symptoms of Vitamin A Deficiency?

Vitamin A deficiency is known to cause xerophthalmia, a form of dry eye affecting the retina and cornea causing low vision in dim light or blindness. But, low vitamin A can also impair your immune system function [3]. Common signs and symptoms include:

• Bumps on the back of the arms
• Recurrent infections and poor immune system function
• Dry eyes
• Night blindness
• Bitot’s spots (the buildup of protein on the eye) 

Lesser-known signs and symptoms may include:

• Poor sleep [8]
• Altered circadian entrainment
• Kidney stones
• Asthma
• Allergies
• Food intolerances
• Low sex hormones
• Autoimmune disease

A severe deficiency of vitamin A can lead to blindness, but this is extremely rare.

If you are experiencing the signs and symptoms of vitamin A deficiency and you are at high risk, it is generally safe to supplement with a modest dose of vitamin A without testing. 

While on the supplement, you should monitor your symptoms for improvement. But it really makes the most sense to test before adding a supplement. A vitamin A deficiency test is inexpensive and fairly accurate in cases of severe deficiency.

Other Deficiencies and Imbalances Can Affect Your Vitamin A Levels

So, why is your serum vitamin A level not responding to vitamin A-rich foods and vitamin A supplementation? Certain micronutrient deficiencies and health considerations may be at play:

• Zinc deficiency can affect the absorption, transport, and utilization of vitamin A [9].
• Iron deficiency may negatively impact serum retinol concentrations and decrease vitamin A mobilization from the liver [2].
• Low dietary protein intake can falsely lower serum retinol levels [10].
• Inflammation and infection can force serum retinol levels to decline due to a decrease in retinol binding protein [3].

If you have a low vitamin A level, it’s important to work with your practitioner to uncover and correct underlying factors.

When Are Vitamin A Supplements Helpful?

In cases of deficiency, vitamin A supplementation may be helpful for several conditions:

• Immune system function: In areas where vitamin A deficiency is a public health concern, high-dose vitamin A supplements decrease the risk of childhood measles in kids ages six months to five years [3].
• Post-infectious loss of smell: One study found 10,000 international units (IU) of intranasal vitamin A improved sense of smell after eight weeks when compared to controls [11]. However, the same dose of vitamin A in oral form did not improve olfactory function significantly compared to the control group [12].
• Dry eye disease: Oral supplementation of 1,500 milligrams (mg) of oral vitamin A for three consecutive days has been shown to improve tear quality test results in patients with dry eye disease [13].
• Skin disorders: Topical and systemic use of vitamin A and its derivatives may be beneficial for acne, psoriasis, keratosis pilaris (tiny bumps and dry rough patches), skin cancer, and ichthyosis (a genetic disorder causing dry, scaly skin) [14, 15].
• Hypothyroidism: In children with both iodine and vitamin A deficiency, vitamin A supplementation along with iodized salt improved thyroid markers and decreased the risk of hypothyroidism [16]. 
• Parkinson’s disease: PD patients who took a combination supplement that included vitamin A for 30 months experienced significantly delayed disease progression compared to controls [17].
• Multiple sclerosis: MS patients receiving 25,000 IU/day of retinyl palmitate for six months followed by 10,000 IU/day retinyl palmitate for another six months experienced significant reductions in depression and fatigue [18].

Vitamin A and beta carotene supplementation may not be helpful and may be harmful in these conditions:

• Cancer: People with higher intakes of vitamin A and beta carotene-rich foods have lower lung cancer risk. However, in one study of smokers and asbestos-exposed individuals, high doses of supplemental beta-carotene and vitamin A were associated with increased lung cancer risk when compared to controls who took no vitamins [19, 20]. Increased prostate cancer risk may exist in those with higher circulating levels of carotenoids and retinol [21, 22].
• Atherosclerosis (hardening of the arteries): In smokers and asbestos-exposed individuals, supplementation with 25,000 IU vitamin A plus 30 mg of beta carotene was associated with a slight increased risk of atherosclerosis. However, the result was not statistically significant [20].

Vitamin A Supplementation Guide and Considerations

The Ancient Egyptians and Greeks cured night blindness with vitamin A-rich roasted oxen liver as early as 460 to 325 BC [3]. Correcting a vitamin A deficiency today can also be accomplished by consuming vitamin A-rich foods, but supplemental beta-carotene and preformed retinol are available as well. 

The daily recommended dietary allowance (RDA) in retinol equivalents is 900 micrograms (mcg) per day or 3,000 IU for adult men and 700 mcg per day or 2,300 IU for adult women [6]. The daily tolerable upper intake level (UL) for adults is set at 3,000 mcg of preformed (animal-based) vitamin A [6].

Taking supplemental vitamin A with other fat-soluble vitamins like vitamins D, E, and K is probably the best practice. Large doses of vitamin A may negatively affect the status of other nutrients. One study found breast-feeding mothers who received 200,000 IU of retinyl palmitate after the first colostrum collection had decreased bioavailability of vitamin E in their breast milk [23].

Those with the following conditions may require higher doses of these fat-soluble vitamins:

• Exocrine pancreatic insufficiency (lack of adequate digestive enzymes leads to the inability to digest food properly)
• Cholestasis (a liver disease where the flow of bile is reduced or blocked)
• Weight loss surgery
• Crohn’s disease 
• Celiac disease
• Other malabsorption disorders of the intestine

Caution with supplemental vitamin A during pregnancy is recommended due to the potential for birth defects. Even though most related birth defects have been linked to women taking greater than 25,000 IU vitamin A per day, pregnant women should not exceed 10,000 IU vitamin A per day [24]. 

If your test results indicate you are vitamin A deficient, work with your healthcare provider to determine your specific supplementation needs. 

Can Supplementation Lead to Vitamin A Toxicity? (Hypervitaminosis A)

A standard supplemental dose of vitamin A is not at all likely to lead to toxicity, especially if you have a suspected or confirmed deficiency. 

Vitamin A is a fat-soluble vitamin meaning it can be stored in the body for long periods, so theoretically, it can become toxic. However, toxicity from over-supplementing with vitamin A is unlikely and is usually the result of extremely high doses (greater than 10 times the RDA) of this vitamin over the course of months to years. 

Vitamin A toxicity symptoms and concerns include:  

• Changes to bone health
• Birth defects
• Fatigue
• Hair loss
• Headache
• Loss of appetite
• Liver disorders
• Upset stomach
• Dry/Itchy/Peeling skin
• Brittle finger nails
• Cracked lips [6, 24, 25]

Serum retinol testing is not accurate for detecting vitamin A toxicity. Since most of your vitamin A is stored in the liver, serum levels can appear normal or even low despite very high liver levels.

If you suspect or are concerned about a toxicity, seek medical attention. But again, vitamin A toxicity is not common and if you’re taking supplemental vitamin A under the care of your healthcare provider, there is generally no need for concern. 

Vitamin A Deficiency May Indicate a Larger Issue

Vitamin A deficiency is rare, but if you are in the high-risk category or have vitamin A deficiency symptoms, you may want to test your serum vitamin A level.

If you’re below the recommended level, improving your vitamin A status is generally easily accomplished by increasing your intake of vitamin A food sources. However, modest supplementation is also safe and effective. 

Continued low serum vitamin A levels despite supplementation may be indicative of a larger issue. For more guidance, schedule an appointment with the Ruscio Institute of Functional Medicine.