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Vitamin C

Vitamins Biomarker

Sample Needed

Collection Type: Blood

Body System

Related System: Vitamins

Overview

Vitamin C (ascorbic acid) is a water‑soluble vitamin and potent antioxidant required for collagen synthesis, iron absorption, neurotransmitter production, and immune function. The blood (plasma/serum) vitamin C test measures circulating ascorbic acid and reflects recent intake and body stores. It is used to detect deficiency (risk of scurvy), monitor supplementation or risk of excess from high-dose therapy, and evaluate causes of unexplained bruising, bleeding gums, poor wound healing, fatigue or anemia. Levels vary with age, smoking (smokers have lower levels and higher requirements), pregnancy/lactation (slightly increased needs), renal function, acute illness/inflammation and dietary patterns; sample handling and recent intake strongly affect results.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: included in the Vitamins profile.
Symptoms that suggest testing: persistent fatigue, swollen/bleeding gums, easy bruising, delayed wound healing, joint pain, corkscrew hairs, or unexplained anemia.
Conditions diagnosed/monitored: vitamin C deficiency/scurvy, nutritional status, monitoring high-dose supplementation.
Reasons for abnormal levels: poor dietary intake, malabsorption, increased metabolic demand (infection, smoking), renal impairment, or excess supplementation.
Biological meaning: low values indicate depleted body stores and impaired collagen/antioxidant function; high values reflect recent large intake or impaired excretion.
Lifestyle/family history: restrictive diets, alcohol dependence, smoking, strict vegetarian/elderly living alone, or a family history of disorders causing malabsorption warrant testing.

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Understanding Test Results

Values <0.2 mg/dL (<11 μmol/L) indicate severe deficiency and are associated with clinical scurvy (gum bleeding, perifollicular hemorrhages, poor wound healing, anemia) and require urgent nutritional correction.
Levels 0.2–0.4 mg/dL (11–23 μmol/L) represent deficiency/low stores and increased risk of symptomatic deficiency.
Values 0.4–0.6 mg/dL (23–34 μmol/L) are borderline/insufficient and suggest inadequate intake.
The reference range 0.6–2.0 mg/dL (34–114 μmol/L) is considered adequate/replete for most people; values near the lower end may benefit from increased dietary intake.
Levels >2.0 mg/dL (>114 μmol/L) usually reflect recent high‑dose supplementation; while not commonly toxic, very high sustained doses can cause gastrointestinal upset, osmotic diarrhea, increased urinary oxalate and risk of kidney stones, and may be problematic in severe renal impairment or certain metabolic conditions.
Note acute illness, smoking and sample handling can lower measured plasma levels and should be considered when interpreting results.

Normal Range

0.6-2.0 mg/dL OR 34-114 μmol/L

FAQs

Q: What foods are highest in vitamin C?

A: Foods highest in vitamin C include guava, red bell peppers, kiwi, strawberries, oranges and other citrus, papaya and pineapple, mango, broccoli, Brussels sprouts, kale, and tomatoes. Fresh, raw fruits and vegetables generally contain more vitamin C than cooked; bell peppers and guava are among the richest per serving. Regularly include a variety for best intake.

Q: How do I get 100% vitamin C?

A: To meet 100% of daily vitamin C, eat a variety of fruits and vegetables providing about 75 to 90 mg per day for most adults. Examples include an orange or kiwi plus bell peppers or strawberries; a 75 to 100 mg supplement can fill gaps. Do not exceed the 2,000 mg upper limit and consult a clinician if pregnant, smoking, or taking medications.

Q: What are the signs of lack of vitamin C?

A: Signs of vitamin C deficiency include persistent fatigue and weakness, irritability, swollen, painful or bleeding gums and loose teeth, easy bruising, slow wound healing, dry, rough or scaly skin with corkscrew hairs and small pinpoint (perifollicular) bleeding, joint or muscle aches, and iron‑deficiency anemia. Advanced deficiency leads to scurvy with severe bleeding, poor tooth and bone health, and impaired immunity.

Q: What are the 5 major functions of vitamin C?

A: Vitamin C functions as a potent antioxidant, supports collagen synthesis for skin, bones and wound healing, enhances immune responses, improves non‑heme iron absorption from plant foods, and is required for synthesis of certain neurotransmitters and carnitine—important for energy metabolism and overall tissue repair. It also contributes to antioxidant recycling and reduces oxidative stress, supporting vascular health.

Q: Which 3 fruits are highest in vitamin C?

A: The three fruits highest in vitamin C are Kakadu plum (very high roughly 1,800–2,300 mg per 100 g), camu camu (about 1,500–2,000 mg/100 g), and acerola (Barbados cherry) (around 1,000–1,700 mg/100 g). These exotic fruits typically contain far more vitamin C than common sources such as oranges, guava, or kiwi.

Q: What is the best drink for vitamin C?

A: The best drink for vitamin C is fresh, 100% citrus juice—especially orange juice; acerola and guava juices contain far higher vitamin C when available. Choose freshly squeezed or cold-pressed, no added sugar, since vitamin C is water‑soluble and heat‑sensitive (pasteurization can reduce content). Remember whole fruits provide fiber; juice is useful for boosting intake in moderation.