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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. Low levels may indicate poor absorption, dietary deficiencies, or health conditions affecting vitamin metabolism.

Quick summary

["Vitamin C helps protect cells and supports immune function; low levels may signal underlying health concerns."]

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

Key facts at a glance

LOINC
35156-9
Short code
Deprecated VLCFA C24:0 SerPl-sCnc
Synonyms
Deprecated VLCFA C24:0 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, assess immune function, evaluate chronic illnesses (like cancer or liver disease), or monitor certain medications that affect vitamin levels. It can also help diagnose or manage scurvy or other conditions linked to low vitamin C.

What to Expect Before the Test

No special preparation is needed unless instructed. You may have blood drawn from a vein in your arm. If you’re on certain medications (e.g., some antibiotics or diuretics), let your provider know, as they could influence results.

What the Results Mean

Results are compared to general reference ranges for healthy adults. Very low levels may require further testing or dietary adjustments, while very high levels could signal conditions like hemochromatosis or certain medications.

Common Causes of Low or High Levels

Low vitamin C can stem from poor diet, smoking, certain medications, or health conditions like Crohn’s disease or malabsorption. High levels may be due to genetic disorders, excessive vitamin supplements, or rare metabolic issues.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin C Level

Frequently asked questions

How often should I get this test?
This test is typically ordered as needed—either for diagnostic purposes (e.g., suspected deficiency) or monitoring (e.g., during chemotherapy or liver disease). Your provider will determine frequency based on your health status and symptoms.
Can I take vitamin C supplements before the test?
Yes, but avoid taking large doses (e.g., megadoses) unless instructed by your provider. Small amounts (e.g., dietary sources or standard supplements) are usually fine, as they won’t significantly alter results.
Does diet affect this test?
Yes, vitamin C is found in fruits and vegetables. While you don’t need to avoid them, avoid excessive intake (e.g., high-dose supplements) or sudden large dietary changes that could skew results. Eat a balanced diet for overall health.
  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