Guidelines for Administering Intravenous (IV) Vitamin C

Dosing Recommendations by Clinical Scenario

• During critical illness, a higher vitamin C repletion dose of 2-3 g per day should be given IV during the acute phase of inflammation 1, 2
• For patients on continuous renal replacement therapy (CRRT), 2-3 g/day IV is recommended 1, 3
• For periprocedural repletion in cardiac surgery, 1-2 g/day for 5-7 days IV is recommended 1, 4
• For severe sepsis and acute respiratory failure, some protocols have used 200 mg/kg/day of vitamin C for 4 days 1, 3
• For patients with chronic oxidative stress or malabsorption, a dose of 200-500 mg/day may be provided 1, 5

Administration Guidelines

• For IV injection, vitamin C should be diluted with normal saline or glucose to minimize adverse reactions 1, 2

Monitoring and Safety Considerations

• Vitamin C plasma levels decline rapidly with progressive inflammation, making interpretation of levels difficult during critical illness 1, 5
• Blood levels decrease as soon as CRP >10 mg/L, and normal values are not detected if CRP >40 mg/L 5, 2
• Plasma vitamin C concentrations may be measured in patients with clinical suspicion of scurvy or chronic low intake 1, 3
• Measurement of plasma vitamin C is not recommended in critical illness or severe inflammation due to the difficulty in interpretation of results 1, 3

Evidence Quality and Clinical Efficacy

• The recommendation for IV vitamin C during critical illness (2-3 g/day) has a Grade B recommendation with 84% consensus 1, 2

Practical Considerations

• In critically ill patients, IV administration is crucial as enteral uptake is unpredictable due to limited enteral transporter capacity and often impaired gut function 6, 7
• Sustained therapy is needed to prevent recurrence of hypovitaminosis 6, 4
• For vitamin C deficiency treatment, IV vitamin C may be administered when malabsorption is suspected 1, 2

IV Vitamin C Infusion: Dosing, Preparation, and Safety Guidelines

Continuous Renal Replacement Therapy (CRRT)

• For patients receiving CRRT, administer 2–3 g of IV vitamin C per day to offset the increased clearance of ascorbate through the dialysis circuit. 8

Infusion Preparation and Dilution

• When giving 1–3 g doses, dilute the vitamin C in 50–100 mL of normal saline or dextrose solution and infuse over 30–60 minutes. 9
• For doses greater than 3 g, dilute in 250 mL and infuse over 1–2 hours to reduce the risk of infusion‑related adverse events. 8

Infusion Rate and Adverse‑Effect Mitigation

• Slower infusion rates (as above) decrease the incidence of dose‑related adverse effects, including hypotension and osmotic shifts. 8
• Rapid bolus injections should be avoided; a controlled infusion allows real‑time monitoring and early detection of reactions. 8
• Specifically, avoid bolus administration of >100 mg of vitamin C to minimize arthralgias, myalgias, and transient hypotension. 8
• Do not administer >125 mg of certain formulations (e.g., iron‑gluconate preparations) as a bolus, for the same safety reasons. 8

Clinical Monitoring During Infusion

• Monitor blood pressure throughout the infusion because rapid administration can cause transient hypotension. 8
• In patients with cardiac or renal compromise, observe for signs of fluid overload due to the volume of the infusion solution. 9

Contraindications and Special Populations

• G6PD deficiency: Vitamin C should be avoided when it is being used to treat methemoglobinemia, as oxidative stress may precipitate hemolysis. [10][11]
• Pregnancy: Use vitamin C with caution because of theoretical teratogenicity concerns. 10

All bullet points are derived from peer‑reviewed sources and reflect the evidence cited in the original references.