Absorbic Acid

Overview

Ascorbic acid (vitamin C) in urine measures how much vitamin C is being excreted by the kidneys and reflects recent dietary intake, supplementation and renal handling. The test helps assess vitamin C status (possible deficiency or excess), monitors high-dose supplementation or intravenous therapy, and can explain unexpected urine dipstick results because ascorbic acid can interfere with some chemical tests. Low urine levels may be seen with poor dietary intake, malabsorption or increased bodily needs; high urine levels typically reflect recent high oral or IV intake or decreased renal reabsorption. Results vary with age, pregnancy (higher requirements), renal function, diet, smoking (lowers body stores) and recent supplement use.

Test Preparation

• Fasting may be required in some labs

Why Do I Need This Test

• Profile: Urine Analysis - Symptoms indicating a test: easy bruising, bleeding gums, poor wound healing, fatigue, or unexplained abnormal urine dipstick results - Conditions it may diagnose/monitor: vitamin C deficiency (risk of scurvy), excess/intoxication from supplements, monitoring of high-dose therapy - Reasons for abnormal levels: inadequate intake, malabsorption or increased requirements (low); recent high-dose supplementation or impaired renal clearance (high) - Biological meaning: low values indicate depleted body stores and functional deficiency; high values reflect surplus that is being excreted - Lifestyle/family history: smoking, restrictive diets, alcohol use, malabsorption syndromes or family history of disorders causing nutrient malabsorption may prompt testing

Understanding Test Results

• <0.2 mg/dL: Suggests significant deficiency and depleted body stores; clinical risk for scurvy (bleeding gums, poor wound healing, petechiae).
• Evaluate diet, malabsorption and consider plasma testing and supplementation.
• 0.2–0.4 mg/dL: Low or borderline may indicate inadequate recent intake or increased requirements; investigate dietary causes, smoking, pregnancy or malabsorption.
• 0.4–2.0 mg/dL: Typical/adequate recent intake and normal renal excretion for most individuals.
• 2.0–10 mg/dL: Elevated usually due to recent high oral/IV supplementation; generally not toxic but indicates surplus excretion.
• Consider reducing dose if unintended.
• >10 mg/dL: Markedly elevated consistent with very high-dose supplementation or IV therapy; may increase risk of oxalate kidney stones in susceptible individuals and can cause interference with urine dipstick tests (false-negative glucose, blood, nitrite, bilirubin).
• Persistent high urine levels in renal impairment warrant nephrology review.
• Note: Spot urine reflects recent intake; a 24-hour collection or plasma ascorbic acid measurement may better define overall status if clinically required.
• Always interpret results with clinical context, diet and renal function.

FAQs