Vitamin C Parenteral Dosing Recommendations

Route of Administration

The current evidence and major guidelines prioritize intravenous (IV) administration over intramuscular (IM) for vitamin C, with IV doses ranging from 100–200 mg /day for maintenance in stable adults to 2–3 g /day during critical illness. 1, 2
The ESPEN Micronutrient Guideline states that vitamin C may be given IM, IV, or subcutaneously when malabsorption is suspected and recommends diluting IV preparations with normal saline or glucose to reduce adverse reactions. 2

For generally healthy adults, a daily maintenance dose of 50–100 mg is suggested. 1, 3
A standard supplementation dose of 500 mg /day is commonly recommended for routine use. 1, 3

(e.g., diabetes, heart failure, smoking, alcoholism, severe COPD, chronic dialysis)

A dose of 200–500 mg /day is advised for patients with chronic oxidative stress. This recommendation carries a Grade GPP strength with 92 % consensus among experts. 1, 2, 3

Acute inflammation in critically ill patients: 2–3 g /day IV during the acute phase (Grade B recommendation, 84 % consensus). 1, 2, 3, 4
Severe sepsis or acute respiratory failure: 200 mg /kg /day for 4 days. 1, 3, 4
Peri‑operative cardiac surgery: 1–2 g /day IV for 5–7 days (Level 1+ evidence). 1, 3, 4

When clinical signs of scurvy are present, approximately 1 g /day for at least one week should be initiated without delay. 1, 2, 3

Reported adult regimens include 0.5 g every 12 h (up to 16 doses) to a single 10 g dose. 5, 6
More common protocols are 1 g every 12 h (≈14 doses) or 1.5–2 g IV administered over 3–4 infusions. 5, 6
Ascorbic acid is endorsed as the treatment of choice when methylene blue is unavailable or contraindicated. 5, 6

Post‑surgical patients may require 200–500 mg /day of vitamin C to maintain adequate levels. 1, 3, 4
For documented deficiency in this group, 100 mg three times daily or 500 mg /day for 1 month is recommended. 7

Plasma vitamin C concentrations fall rapidly during inflammation (CRP > 10 mg/L) and become difficult to interpret when CRP > 40 mg/L. 2, 4
Routine plasma vitamin C measurement is not recommended in critically ill or severely inflamed patients (Grade GPP, 92 % consensus). 1, 2, 3
Measurement may be considered in individuals with clinical suspicion of scurvy or chronic low intake. 1, 2, 3

For IV delivery, dilute vitamin C with normal saline or glucose to minimize adverse reactions. 2
Although IM administration is listed as an option, specific IM dosing protocols are not well‑established in current guidelines. 2