We read with great interest the recent letter to Critical Care by Marik and Hooper. Vitamin C is increasingly recognized as a crucial compound to alleviate morbidity in critically ill patients. Vitamin C concentrations, however, are usually far below normal and even close to “scurvy levels” in this population. Vitamin C also is substantially cleared by continuous renal replacement therapy (CRRT). Significant vitamin C deficiency was observed in 80% of patients subjected to various types of CRRT despite receiving a daily intravenous (IV) supplement of 500 to 1000 mg. Therefore, high-dose (from 6 to 12 g) vitamin C substitution during CRRT seems justified.

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