Vitamin C infusions

RACGP position: There is no evidence to support vitamin C infusions for routine clinical use. In general practice, do not administer IV vitamin C unless it is part of a properly governed clinical trial with human research ethics approval. [RACGP First Do No Harm – Vitamin C infusions]

What is vitamin C?

Vitamin C, or ascorbic acid, is an essential water-soluble nutrient.

It is involved in:

• collagen synthesis
• wound healing
• nervous system function
• energy metabolism
• antioxidant/free-radical scavenging functions

Humans cannot synthesise vitamin C and must obtain it from diet. Most Australians receive adequate vitamin C through fruit and vegetables, especially citrus fruits and fresh vegetables.

Deficiency: scurvy

Severe deficiency over months can cause scurvy.

Features include:

• weakness
• lethargy
• severe joint or leg pain
• bleeding gums
• easy bruising
• spontaneous bleeding

Scurvy is now rare in Australia but may occur in severe dietary restriction, alcohol dependence, eating disorders, food insecurity, frailty, or restrictive diets.

Why vitamin C infusions are promoted

High-dose IV vitamin C has been proposed for:

• cancer treatment
• COVID-19
• sepsis
• herpes zoster
• fatigue
• “immune boosting”
• cardioprotection before percutaneous coronary intervention

However, RACGP states that these uses should not be offered in routine general practice because there is no high-quality evidence of clinically meaningful benefit.

Evidence summary

Cancer

Early observational reports from the 1970s suggested possible benefit from high-dose vitamin C, but later controlled studies did not reproduce clear survival or tumour-response benefits.

The National Cancer Institute notes that:

• early case series appeared promising
• early randomised trials using oral vitamin C did not show significant differences in symptoms, performance status, or survival
• laboratory studies show possible anti-cancer effects at pharmacological concentrations
• human studies remain limited by trial-design weaknesses
• IV vitamin C has generally been well tolerated in clinical trials, but evidence is insufficient to recommend it as cancer therapy [National Cancer Institute PDQ – Health Professional Version]

a 2021 systematic review of vitamin C in cancer treatment did not demonstrate important clinical benefit for tumour or disease progression. https://pmc.ncbi.nlm.nih.gov/articles/PMC12998572/

COVID-19

No high-quality evidence shows that IV vitamin C improves outcomes in COVID-19. Therapeutic Goods Administration has stated there is no evidence to support intravenous high-dose vitamin C in COVID-19 management.

Sepsis

IV vitamin C has been studied in sepsis and severe acute respiratory failure, but evidence has not established routine clinical benefit. RACGP does not recommend IV vitamin C for sepsis outside clinical trials.

Herpes zoster and other proposed uses

Current evidence does not support IV vitamin C for herpes zoster or other promoted indications.

Why IV vitamin C is different from oral vitamin C

Oral vitamin C has limited absorption and regulated plasma levels. IV administration bypasses this control and can produce much higher plasma ascorbate concentrations.

The NCI notes that IV doses above 500 mg can produce much higher blood concentrations than the same dose taken orally. This is part of the theoretical rationale for IV use, but pharmacological plausibility does not equal proven clinical benefit. [National Cancer Institute PDQ]

Harms and contraindications

Kidney stones

Ascorbic acid is metabolised to oxalic acid, which can form calcium oxalate crystals. This may increase the risk of renal stones, especially in patients with renal impairment.

Worsening renal function

Renal failure has been reported after vitamin C treatment in patients with pre-existing renal disease. Avoid IV vitamin C in patients with renal impairment or high renal-stone risk.

G6PD deficiency

High-dose IV vitamin C can cause significant haemolysis in people with glucose-6-phosphate dehydrogenase deficiency.

Clinical point: G6PD deficiency is a contraindication to IV vitamin C.

Haemochromatosis

High-dose vitamin C can increase iron absorption and may worsen iron-induced tissue damage in haemochromatosis.

Clinical point: Avoid IV vitamin C in haemochromatosis or significant iron overload.

Cancer-treatment interactions

Vitamin C may interact with some cancer therapies.

Important example:

• Bortezomib, used in multiple myeloma: vitamin C may reduce its efficacy. Patients receiving bortezomib should not receive vitamin C infusions.
• Cancer patients considering IV vitamin C should discuss this with their oncologist before proceeding.

Common side effects

Reported side effects include:

• nausea
• vomiting
• headache
• injection-site discomfort

These may appear mild, but the major concern is the risk of serious harm in susceptible patients, especially renal impairment, G6PD deficiency and haemochromatosis.

Is there a recommended dose?

No.

Because IV vitamin C is not recommended for any routine clinical indication, there is no agreed optimal:

• dose
• frequency
• duration
• monitoring schedule

This is a key counselling point when patients ask about protocols from private infusion clinics.

Medicare coverage

Vitamin C infusions are not covered by Medicare. Patients generally pay privately.

GP approach to patient requests

1. Explore the patient’s reason

Ask:

• “What are you hoping the infusion will help with?”
• “Where did you hear about it?”
• “Are you using it for cancer, fatigue, immunity, infection prevention, or another reason?”
• “Are you currently seeing a specialist or receiving chemotherapy/immunotherapy?”

2. Validate concerns without endorsing treatment

Example:

“I can understand why this sounds appealing, especially when you are looking for something active to improve your health. The difficulty is that the evidence does not show that vitamin C infusions improve outcomes, and there are some real risks in certain people.”

3. Explain the evidence clearly

Key wording:

• “Vitamin C is essential, but most people get enough through diet.”
• “Low vitamin C can cause scurvy, but that is different from using high-dose IV vitamin C as a treatment.”
• “RACGP does not recommend IV vitamin C in general practice because benefit has not been shown.”
• “For cancer, COVID-19 and sepsis, evidence does not support routine use outside clinical trials.”

4. Discuss risk groups

Avoid or strongly discourage IV vitamin C in patients with:

• chronic kidney disease
• history of renal stones
• G6PD deficiency
• haemochromatosis or iron overload
• multiple myeloma treated with bortezomib
• active cancer treatment without oncologist approval

5. Offer safer evidence-based alternatives

Depending on the patient’s goal:

• assess diet and nutrition
• encourage adequate fruit and vegetable intake
• check for genuine deficiency if clinically suspected
• optimise management of underlying conditions
• address fatigue with evidence-based assessment
• encourage cancer patients to discuss complementary therapies with their oncologist
• support shared decision-making and avoid therapeutic conflict

Bottom line

• Vitamin C is essential, but deficiency is uncommon in Australia.
• IV vitamin C is not recommended in general practice.
• Evidence does not support routine IV vitamin C for cancer, COVID-19, sepsis, herpes zoster or general “immune boosting”.
• Potential harms include renal stones, renal impairment, haemolysis in G6PD deficiency, worsening iron overload, and interaction with cancer therapy.
• Use a respectful counselling approach: explore beliefs, explain evidence, discuss risks, and redirect to evidence-based care.