Vitamin C infusions

Renal stones

Ascorbic acid is metabolised to oxalic acid, which can form calcium oxalate crystals, particularly in patients with renal dysfunction.^1,2

Worsening kidney function

Renal failure after vitamin C treatment has been reported in patients with pre-existing renal disorders.³

Haemolysis in people with glucose-6-phosphate dehydrogenase (G6PD) deficiency

People with G6PD deficiency should not receive vitamin C infusions because high doses of intravenous vitamin C can result in significant haemolysis of red blood cells.^1,4,5

Iron overload in patients with haemochromatosis

Studies show that high-dose vitamin C increases the absorption of iron, which could worsen iron-induced tissue damage in those with haemochromatosis.⁴ 

Drug interactions that may lead to lowering the efficacy of bortezomib

As vitamin C can interact with the drug bortezomib (used as first-line treatment for multiple myeloma) and reduce the drug’s efficacy, it should not be administered with bortezomib.^4,6

Vitamin C, also known as ascorbic acid, is an essential water-soluble nutrient that acts as an antioxidant and a free radical scavenger.⁴ Because of these properties, some researchers believe that it could be used as a treatment for cancer, sepsis, herpes zoster infection, COVID-19 and for cardio protection prior to percutaneous coronary intervention.

Although results of studies in the 1970s reported that treatment with megadoses of oral vitamin C improved quality of life and survival rate of people with cancer,^7–9 these results were not demonstrated in subsequent double-blinded randomised trials.^8,10,11 More recent studies focusing on intravenous administration of vitamin C¹² and – significantly – a 2021 systematic review of vitamin C and cancer treatment have all demonstrated that these treatments do not deliver any important clinical benefit for tumour or disease progression.¹³

In addition, current evidence does not support the use of high-dose vitamin C in patients with COVID-19,¹⁴ or herpes zoster.¹⁵

• Discuss with the patient what they think high-dose vitamin C will do for them, and based on their specific situation or concern, discuss other evidence-based treatments and supports that are appropriate.
• Encourage patients with cancer to discuss evidence-based treatments with their oncologist.

• The RACGP, First do no harm: A guide to choosing wisely in general practice, Vitamin C infusions patient resource
• Chapman K, Vitamin pills’ role in recovering from cancer, The Conversation 
• National Cancer Institute (US), Intravenous vitamin C (PDQ®) – Patient version
• Therapeutic Goods Administration, No evidence to support intravenous high-dose vitamin C in the management of COVID-19
•  Fowler AA, Truwit JD, Hite RD, et al. Effect of vitamin C infusion on organ failure and biomarkers of inflammation and vascular injury in patients with sepsis and severe acute respiratory failure: The CITRIS-ALI randomized clinical trial 
• Hoppe C, Freuding M, Büntzel J, Münstedt K, Hübner J. Clinical efficacy and safety of oral and intravenous vitamin C use in patients with malignant diseases
• National Cancer Institute (US), Intravenous high-dose vitamin C in cancer therapy    
• National Cancer Institute (US), Intravenous vitamin C (PDQ®) – Health professional version