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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, an essential antioxidant, in your blood. Low levels may indicate poor absorption, certain medical conditions, or increased vitamin C loss through urine.

Quick summary

["Vitamin C supports immunity, skin health, and iron absorption—low levels may signal nutritional concerns or health risks."]

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

Key facts at a glance

LOINC
12482-6
Short code
Vit C WBC-mCnc
Synonyms
Vit C WBC-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
4.5
Ref high
11
Critical range
2 N/A – 30 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85004
SNOMED
900000000000003002
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 nutrient absorption issues, or evaluate conditions like scurvy, chronic illnesses, or heavy smoking. It can also help monitor vitamin C supplementation.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm for a blood draw. If you’re fasting, follow your provider’s instructions to avoid misleading results.

What the Results Mean

Results show your vitamin C concentration in milligrams per deciliter (mg/dL). While reference ranges vary by lab, very low levels may warrant further investigation into diet, absorption, or underlying health problems.

Common Causes of Abnormal Results

Low vitamin C levels can result from poor diet, gastrointestinal disorders, heavy smoking, or certain medications. High levels may occur with excessive vitamin C intake or rare genetic conditions.

Reference range

Adult: 4.5-11.0 x 10^9/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum/Plasma Vitamin C

Frequently asked questions

What triggers a vitamin C blood test?
Your doctor may recommend this test if you have symptoms like fatigue, frequent infections, or skin problems, or if you’re taking medications that affect vitamin absorption.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab and insurance. Follow-up may be needed if results are outside expected ranges.
Can diet affect vitamin C test results?
Yes—eating vitamin C-rich foods (like citrus fruits) or taking supplements shortly before testing can raise your levels. Fasting may be advised if your provider specifies it.
  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