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Blood Test Tracker

Vitamin A (Retinol)

Measures retinol, the main blood form of vitamin A, which supports vision, immune defenses and skin and is mostly stored in the liver.

AI-verified against cited sources. Awaiting expert reviewAlso called Vit ALOINC 2923-1

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What it is

Vitamin A comes ready-made as retinol in liver, fish, eggs and dairy, and as carotenoids from orange, yellow and leafy green plants that the body converts. Most of it is stored in the liver, and the liver releases it into the blood as needed. Because the liver keeps blood retinol within a narrow range, this test is a rough guide to your stores rather than an exact measure.

Why it matters

Vitamin A is needed for vision in dim light, for immune defenses and for healthy skin and growth. Deficiency is uncommon in the US but is a leading cause of preventable blindness in some parts of the world. Too much ready-made vitamin A over time can harm the liver and bones, and it can cause birth defects in pregnancy.

If it’s low

A low result means your blood is carrying less vitamin A than usual. Because the liver holds large reserves, a low blood level often means stores are running down, or that something is blocking absorption or transport. Early signs of a shortage are poor vision in dim light and dry eyes.

Common causes

  • A diet low in vitamin A-rich foods
  • Infection or inflammation, which can lower blood levels for a while
  • Conditions that reduce fat absorption, such as celiac disease, Crohn's disease, cystic fibrosis or other pancreas problems
  • Liver disease, which affects both storage and transport
  • Low protein intake or low zinc, which can reduce the carrier protein

What can help

  • Talk with a clinician about the likely cause and whether a supplement is right for you
  • Eat vitamin A-rich foods such as eggs, dairy, fish and orange, yellow and leafy green vegetables
  • Ask whether and when to recheck the level

If it’s high

A high result most often comes from vitamin A supplements, or from a sample taken without fasting. Modest rises do not by themselves show toxicity, and there is no widely accepted blood level that defines it. Long-term excess intake can cause dry skin, hair loss, headaches, bone and joint pain and liver problems.

Common causes

  • High-dose vitamin A supplements, including some multivitamins
  • Not fasting before the test, or alcohol in the 24 hours before the draw
  • Reduced kidney function, which can raise retinol

What can help

  • Review all your supplements and their vitamin A content with a clinician
  • Ask whether a repeat test after a proper fast would help
  • Tell your clinician about any retinoid medicine, such as one used for acne or psoriasis

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on age. Choose an age to see the one that applies.

Children and teens 3 ranges

See Vitamin A by age and sex, with the U.S. survey numbers where they exist.

NIH Office of Dietary Supplements deficiency cutoffs (serum or plasma retinol)

  • Severe deficiencybelow 10 µg/dL
  • Moderate deficiency10 to under 20 µg/dL
  • Above the deficiency cutoffs20 and above µg/dL

If this applies to you

Vitamin A means a little more for some people. Open the one that fits you.

Had weight-loss surgery

Vitamin A is one of the fat-soluble vitamins, and low levels are most common after duodenal switch and gastric bypass. ASMBS suggests checking it in the first year after surgery, especially after duodenal switch.

Blood tests after weight-loss surgery

How common is your level?

NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.

How Vitamin A varies with age in the U.S.Shaded: middle 90% and middle 50% of people. Line: the median. µg/dL. Point at any age, or focus the chart and use the arrow keys, to read both sexes in words.

Use the left and right arrow keys to read each age. Shift moves five years.

Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2017-2018. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.

Explore Vitamin A by age and sex: every percentile as a table, with a download.

What can affect your result

  • Fasting: a meal can raise the result, so labs ask for a 12-hour fast
  • Alcohol in the 24 hours before the draw
  • Vitamin A supplements and multivitamins
  • Infection or inflammation, which can lower blood retinol
  • Kidney and liver function
  • Age: children have lower usual ranges than adults
  • Not fasting, recent vitamin A supplements, or alcohol in the 24 hours before the draw can raise the result; labs ask for a 12-hour fast and no alcohol for 24 hours.
  • Infections and inflammation can lower blood retinol without any change in your stores.
  • Reduced kidney function can raise retinol and its transport protein.

Blood retinol is tightly controlled, so it changes slowly. It may not move until liver stores are nearly used up or heavily loaded.

When to talk to a clinician

See a clinician soon if your level is at or below 10 µg/dL (0.35 µmol/L), which the NIH calls severe deficiency, or if you have trouble seeing in dim light or very dry, irritated eyes. If you take vitamin A supplements and have a severe headache, blurred vision, nausea or bone and joint pain, or you are pregnant or planning pregnancy, tell your clinician about the supplement.

Questions you could ask

  • Does my vitamin A level matter for my other conditions, medicines or any plans for pregnancy?
  • Could my supplements, or not fasting, explain this result?
  • Should we repeat the test after a proper fast?
  • Could my diet or a digestive or liver condition explain this level?
  • Do I have any signs of a shortage, such as trouble seeing in dim light?
  • When should we recheck it?

Questions people ask

Why can my vitamin A be normal if I eat very little of it?

Your liver stores a large reserve and keeps the blood level steady. The level in your blood usually stays in range until those reserves are nearly used up, so a normal result does not rule out a low store.

Why was I told to fast and skip alcohol?

Eating, supplements and alcohol can raise the measured level. Mayo Clinic Laboratories sets its reference range using fasting samples, so a fasting draw gives the fairest comparison.

How do I convert µg/dL to µmol/L?

Multiply µg/dL by 0.0349, so 30 µg/dL is about 1.05 µmol/L. If your report is in mg/L (as ARUP prints it), multiply by 100 to get µg/dL.

Show the science and sources

Units

  • 1 µg/dL = 1 µg/dL
  • 1 µg/dL = 0.0349 µmol/L
  • 1 µg/dL = 0.01 mg/L
  • 1 µg/dL = 10 µg/L

Open the Vitamin A unit converter

Is a change real?

Vitamin A naturally varies about 13.6% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 42% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Desirable Biological Variation Database specifications, 2014 update (Minchinela J, Ricos C, et al.; the 'Ricos database', a compilation of median published CVI/CVG).

For clinicians and researchers

Retinol circulates bound to retinol-binding protein and is homeostatically controlled, so serum retinol falls only when liver stores are nearly depleted and can be lowered by acute or chronic infection without a true deficit (NIH ODS); liver reserves are the best measure of adequacy. NIH ODS gives 20 µg/dL (0.70 µmol/L) or less as frequently reflecting moderate deficiency and 10 µg/dL (0.35 µmol/L) or less as severe, and notes under 1% of the US population is below 20 µg/dL. Mayo Clinic Laboratories' adult interval is 32.5 to 78.0 µg/dL by LC-MS/MS on fasting samples, and its report cites 20 µg/dL as the WHO level below which supplementation is recommended and under 10 µg/dL as severe deficiency. ARUP prints 0.30 to 1.20 mg/L for adults, calls levels above 0.30 mg/L generally consistent with adequate stores and below 0.10 mg/L severe deficiency, and also reports retinyl palmitate (0 to 0.10 mg/L). ARUP notes modest rises may follow recent supplementation or impaired renal function, that retinyl palmitate does not reliably track supplement dose, and that no universal serum retinol level defines toxicity.

LOINC 2923-1 (primary), 14905-4. Specimen: serum-or-plasma.

Sources

  1. Vitamin A, Serum (test VITA), Mayo Clinic Laboratories
  2. Vitamin A (Retinol), Serum or Plasma (test 0080525), ARUP Laboratories
  3. Vitamin A and Carotenoids: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements
  4. Retinol (compound summary, molecular weight), PubChem, National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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