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Serum or plasma mass concentration of free active vitamin C (ascorbic acid)

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

This test measures the amount of free, biologically active vitamin C in your blood. Vitamin C is an essential antioxidant that helps protect cells from damage and supports immune function.

Quick summary

["Checks your body’s natural vitamin C levels for potential deficiencies or excesses."]

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

Key facts at a glance

LOINC
3217-7
Short code
Fact X PPP-aCnc
Synonyms
Fact X PPP-aCnc
Category
chemistry
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
coag
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 This Test Matters

Vitamin C is crucial for maintaining immune health, wound healing, and skin integrity. Low levels may indicate poor absorption, dietary deficiencies, or increased oxidative stress. High levels could suggest over-supplementation or certain medical conditions.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your lab requires it. Wear a comfortable shirt for easy access to your vein.

Common Causes of Results Outside Normal Range

Low levels might be linked to malnutrition, certain medications (like some antibiotics or blood thinners), or chronic illnesses. High levels could result from excessive vitamin C intake or rare genetic disorders.

How Results Are Used in Care

Doctors may use these results to diagnose or monitor conditions like scurvy (vitamin C deficiency), assess immune function, or guide treatment for oxidative stress-related diseases.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Vitamin C plays a key role in immune defense, collagen synthesis, and antioxidant protection. Abnormal levels may signal underlying health concerns that require medical attention.

Short name

Free Vitamin C Level

Frequently asked questions

What does a low vitamin C level mean for my health?
A low level may indicate a deficiency, which could weaken your immune system or slow wound healing. Your doctor may recommend dietary changes, supplements, or further testing to address the cause.
Can I take vitamin C supplements if my test is high?
High levels could be harmless, but they may also suggest over-supplementation. Always check with your doctor before adjusting supplements, as excess vitamin C can sometimes cause digestive issues or kidney strain.
Does stress or illness affect vitamin C levels?
Yes, stress, infections, or chronic illnesses can deplete vitamin C stores. If you’re feeling unwell or have a condition like Crohn’s disease, your levels might be lower than usual.
  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