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Vitamin C (Ascorbic Acid) in Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of vitamin C, a powerful antioxidant, in your blood serum. Vitamin C helps protect cells from damage and supports immune function.

Quick summary

["Vitamin C levels can help assess immune health and detect deficiencies."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
35159-3
Short code
Deprecated VLCFA C22:0 SerPl-sCnc
Synonyms
Deprecated VLCFA C22:0 SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for vitamin C deficiency, monitor immune function, or evaluate conditions like scurvy, certain infections, or malabsorption disorders. It can also be part of routine health checks or before surgery to prevent complications.

What Does a Low or High Level Mean?

Low levels may indicate vitamin C deficiency, which can weaken immunity, cause fatigue, or lead to skin problems. High levels might suggest over-supplementation or certain liver conditions, though this is less common.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The serum portion is separated and tested for vitamin C using a specialized lab method.

What Are Common Causes of Abnormal Results?

Deficiency can result from poor diet, certain medications (like some antibiotics or diuretics), or conditions affecting absorption. Overconsumption of vitamin C supplements can also raise levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Vitamin C

Frequently asked questions

Can vitamin C levels change with diet?
Yes, diet plays a major role. Foods rich in vitamin C (like citrus fruits, bell peppers, and leafy greens) can influence results. Avoiding supplements for a few days before testing may help get a more accurate baseline.
How soon after eating do I need to fast for this test?
Typically, fasting is not required for this test, but follow your lab’s instructions—some may recommend avoiding high-vitamin C foods for 24 hours before testing to avoid interference.
Does this test detect vitamin C deficiency in children?
Yes, this test can be used in children to check for vitamin C deficiency, especially in cases of poor diet, illness, or certain genetic conditions that affect nutrient absorption.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy