Safe Dose Range for Vitamin C
The safe dose range for vitamin C is 40-2000 mg per day for healthy adults, with 75-90 mg/day being the recommended daily intake for most individuals and 2000 mg/day considered the tolerable upper intake level. 1, 2
Recommended Daily Intake
- The recommended daily allowance (RDA) for vitamin C varies by country and organization, ranging from 40 to 220 mg per day 1
- Current US recommendations are 75 mg/day for women and 90 mg/day for men 1
- European Food Safety Authority (EFSA) recommends 95 mg/day for women and 110 mg/day for men 1
- For smokers, higher intake is recommended: 135 mg/day for female smokers and 155 mg/day for male smokers due to increased metabolic losses (40% higher turnover) 3
Minimum vs. Optimal Intake
- 40-45 mg/day is considered the minimum to prevent scurvy (vitamin C deficiency disease) 1
- Higher intakes of 90-120 mg/day are recommended for optimum reduction of chronic disease risk 4, 5
- Some research suggests optimal intake may be between 250-500 mg/day for antioxidant benefits and immune function 6
Special Populations
- Pregnant women (from fourth month): 105 mg/day 3
- Lactating women: 125 mg/day 3
- Children under 12 years: Consult a doctor 7
- Children aged 1 to under 15 years: 20-85 mg/day (increasing with age) 3
- Adolescents (15-19 years): 105 mg/day for males, 90 mg/day for females 3
Upper Limits and Safety
- The tolerable upper intake level (UL) is 2000 mg/day for adults 2
- Vitamin C is generally safe across a broad range of intakes up to 2000 mg/day 2
- Adverse effects at high doses may include gastrointestinal upset or mild diarrhea due to osmotic effects of unabsorbed vitamin C 2
Clinical Scenarios Requiring Higher Doses
- Patients with chronic oxidative stress (diabetes, smoking, heart failure, alcoholism, severe COPD, chronic dialysis): 200-500 mg/day 1
- Critically ill patients: 2-3 g/day IV during acute inflammation 1, 8
- Patients on continuous renal replacement therapy: 2-3 g/day IV 1, 8
- Cardiac surgery (periprocedural): 1-2 g/day IV for 5-7 days 1, 8
Supplementation Guidelines
- Standard over-the-counter vitamin C supplements typically contain 500 mg per tablet 7
- For healthy adults and children 12 years and over: 500 mg (1 tablet) daily or as directed by a doctor 7
Monitoring Considerations
- Plasma vitamin C levels are difficult to interpret during inflammation or critical illness 8, 9
- Testing is recommended only for suspected scurvy or chronic low intake 9
- Blood levels decrease when C-reactive protein (CRP) >10 mg/L, and normal values are typically not detected if CRP >40 mg/L 9
Common Pitfalls
- Oral vitamin C absorption is limited at higher doses due to saturation of intestinal transporters 8
- IV administration is necessary in critical illness as enteral uptake is unpredictable 8
- Vitamin C samples require special handling (immediate processing, protection from light, cold storage) for accurate measurement 9