Vitamin C (Ascorbic Acid) Plasma Concentration
This test measures the amount of vitamin C, a powerful antioxidant, in your blood plasma. Low levels may indicate poor absorption, certain medical conditions, or increased vitamin C loss through urine.
["Vitamin C helps protect your cells and supports immune function—low levels may signal health concerns."]
Key facts at a glance
- LOINC
- 4131-9
- Short code
- Vit C PO Dose
- Synonyms
- Vit C PO Dose
- 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 This Test Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms like fatigue, frequent infections, or bleeding gums, or if you’re taking certain medications that affect vitamin C levels. It’s also used to monitor vitamin C deficiency or to check for conditions like scurvy or certain cancers that may alter vitamin C metabolism.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw. Wear a loose shirt for easy access to your arm. Avoid taking vitamin C supplements for 24 hours before the test if instructed by your provider.
What to Expect During the Test
A healthcare professional will insert a small needle into your vein (usually in your arm) to draw a blood sample. The process takes a few minutes and may cause a brief pinch or discomfort. You’ll be asked to sit or lie down while the blood is collected.
What to Expect After the Test
After the blood is drawn, the needle will be removed, and pressure will be applied to the site to stop any bleeding. You can usually return to your normal activities immediately. If you experience excessive bruising or pain, contact your provider.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low vitamin C levels may indicate vitamin C deficiency, which can weaken your immune system, cause skin problems, or contribute to chronic conditions like heart disease or certain cancers. High levels may suggest overconsumption of vitamin C supplements or certain medical conditions. Your provider will interpret results in the context of your overall health and symptoms.
Short name
Vitamin C Level
Frequently asked questions
What does a low vitamin C level mean?
How can I increase my vitamin C intake?
Is there anything I should avoid before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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