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Vitamin C (Ascorbic Acid) in Serum or Plasma

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

This test measures the amount of vitamin C (ascorbic acid) in your blood, which helps support your immune system, skin health, and iron absorption.

Quick summary

["Vitamin C levels can indicate nutritional status and potential deficiencies or excesses."]

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

Key facts at a glance

LOINC
56779-2
Short code
Vit C Smn-sCnc
Synonyms
Vit C Smn-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 if you have symptoms of vitamin C deficiency (like fatigue, bruising, or slow wound healing), if you have certain medical conditions (like malabsorption or chronic illness), or if you’re planning a pregnancy to ensure adequate vitamin intake. It may also be used to monitor vitamin C levels in people taking supplements or with known deficiencies.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for a few hours before the blood draw, but always follow your provider’s instructions. Avoid taking vitamin C supplements 24 hours before testing if possible, as this could affect results.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The blood sample will be sent to a lab for analysis.

What Do the Results Mean?

Results are compared to a general reference range for vitamin C in blood. Low levels may suggest poor diet, malabsorption issues, or certain medical conditions. High levels could indicate excessive intake or rare metabolic disorders. Your provider will interpret results in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Serum or Plasma Vitamin C Level

Frequently asked questions

What causes low vitamin C levels?
Low vitamin C levels can result from dietary deficiencies (e.g., poor fruit/vegetable intake), malabsorption disorders (like celiac disease or Crohn’s), chronic illnesses (e.g., kidney disease), or excessive vitamin C loss (e.g., heavy sweating or diarrhea). Smoking and certain medications may also contribute.
What causes high vitamin C levels?
High vitamin C levels are less common but can occur with overconsumption of supplements, certain genetic disorders, or rare metabolic conditions. In most cases, elevated levels are harmless but warrant monitoring to avoid potential side effects (e.g., nausea, diarrhea).
How often should I get this test?
Your provider will determine the frequency based on your health status. Typically, routine vitamin C screening isn’t standard unless you have risk factors (e.g., pregnancy, chronic illness, or known deficiencies). Follow-up may be needed if results are outside expected ranges.
  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