First Do No Harm: a guide to choosing wisely in general practice

GP Resources

Vitamin C infusions

For GPs

The use of vitamin C infusions as a treatment.

RACGP position

There is no evidence to support the use of vitamin C infusions.

While high-dose vitamin C infusions have been proposed as part of treatment for various conditions (for example, cancer, COVID-19, sepsis and herpes zoster infection and cardio protection before percutaneous coronary intervention), these should only be conducted under the governance of a well-conducted clinical trial with ethics approval.

 Traffic lights


Do not take this action

  • Do not administer vitamin C infusions in general practice settings, unless part of a properly administered clinical trial with human ethics committee approval.


Under specified circumstances,
take this action

  • If a patient has questions about vitamin C infusions as a treatment:

- discuss the patient’s diet, explain the importance of good nutrition and encourage them to have an adequate dietary intake of vitamin C
- discuss their health beliefs and explain the lack of high-quality evidence for infusion therapy.


Take this action

  • If a patient is particularly interested in having vitamin C infusions, explain to them that vitamin C infusions can interact with some treatment regimens, and encourage them to talk about this with their non-GP specialists, including their oncologist if they are a cancer patient.

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.
  1. Bazzan AJ, Zabrecky G, Wintering N, Newberg AB, Monti DA. Retrospective evaluation of clinical experience with intravenous ascorbic acid in patients with cancer. Integr Cancer Ther 2018;17(3):912–20.
  2. Carr AC, Cook J. Intravenous vitamin C for cancer therapy – Identifying the current gaps in our knowledge. Front Physiol 2018;23(9):1182.
  3. National Cancer Institute. Intravenous vitamin C (PDQ®) – Health professional version. National Cancer Institute, 2021 [Accessed 1 April 2022].
  4. National Cancer Institute. High-dose vitamin C (PDQ®) – Patient version. National Cancer Institute, 2021 [Accessed 30 March 2022].
  5. Quinn J, Gerber B, Fouche R, Kenyon K, Blom Z, Muthukanagaraj P. Effect of high-dose vitamin C infusion in a glucose6-phosphate dehydrogenase-deficient patient. Case Rep Med 2017;2017:5202606
  6. Perrone G, Hideshima T, Ikeda H, et al. Ascorbic acid inhibits antitumor activity of bortezomib in vivo. Leukemia 2009;23:1679–86.
  7. Cameron E, Pauling L. Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci USA 1976;73(10):3685–89.
  8. Cantley L, Jihye Y. Intravenous high-dose vitamin C in cancer therapy. National Cancer Institute, 2021 [Accessed 5 April 2022].
  9. Mastrangelo D, Pelosi E, Castelli G, Lo-Coco F, Testa U. Mechanisms of anti-cancer effects of ascorbate: Cytotoxic activity and epigenetic modulation. Blood Cells Mol Dis 2018;69:57–64.
  10. Creagan ET, Moertel CG, O'Fallon JR, et al. Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer. A controlled trial. N Engl J Med 1979;301(13):687–90.
  11. Moertel CG, Fleming TR, Creagan ET, et al. High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who have had no prior chemotherapy. A randomized double-blind comparison. N Engl J Med 1985;312(3):137–41.
  12. Codini M. Why vitamin C could be an excellent complementary remedy to conventional therapies for breast cancer. Int J Mol Sci 2020;21(21):8397.
  13. 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. J Cancer Res Clin Oncol 2021;147(10):3025–42.
  14. National COVID-19 Clinical Evidence Taskforce. Australian guidelines for the clinical care of people with COVID-19 [version 57]. National COVID-19 Clinical Evidence Taskforce 2022 [Accessed 26 October 2022].
  15. Kim MS, Kim DJ, Na CH, Shin BS. A study of intravenous administration of vitamin C in the treatment of acute herpetic pain and postherpetic neuralgia. Ann Dermatol 2016;28(6):677–83.
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