← All insights

Should IV vitamin C be used for cancer patients? Benefits, risks and the bigger picture

Vitamin C and cancer is one of the most argued topics in medicine. This article starts with what IV dosing can do that tablets cannot, then works through evidence, safety, and the bigger terrain beyond any single treatment.

Dr Shehan Wijesingha · · Reading time ~ 14 minutes

In this article

Key takeaways

  • Linus Pauling was one of the first major scientists to publish clinical data on high-dose vitamin C and cancer, but later trials used oral vitamin C, which does not reach the same blood concentrations as intravenous treatment.
  • At pharmacological concentrations, intravenous vitamin C appears to work by generating hydrogen peroxide around cancer cells, increasing their chance of cell death, while leaving healthy cells more intact through the mechanisms explained in this article.
  • The evidence suggests intravenous vitamin C may improve quality of life and treatment tolerance, whilst potentially improving clinical outcomes.
  • If you are considering intravenous vitamin C, look carefully at who is overseeing it, how well they understand your case and what other options they have available to support you.

Vitamin C and cancer: the Linus Pauling controversy

This is one of the more contested questions in cancer care, and it begins with Linus Pauling. Pauling was among the first major scientists to put forward clinical data on high-dose vitamin C and cancer, and he came to it with unusual standing: he had already won the Nobel Prize in Chemistry for his work on chemical bonding, and later the Nobel Peace Prize for his opposition to nuclear weapons testing.1, 2

In 1976, he and the Scottish surgeon Ewan Cameron reported that patients with terminal cancer lived longer when they were given vitamin C into a vein and then by mouth.3 The Mayo Clinic set out to test the idea, gave the vitamin C by mouth alone, found no benefit, and for many that seemed to close the case.4, 5 What we understand now is that giving vitamin C through a vein and giving it by mouth are not the same thing at all, and that one distinction sits underneath everything that follows.

None of this was part of my medical training. So I went and read the research for myself, slowly and properly, and what follows is what I found, in plain language, with the key papers set alongside for anyone who wants to go deeper.

Patients often reach me having already read a great deal, sometimes arriving with a bag of supplements and a long list of things they have come across online. My hope is that this gives you enough to weigh it all up honestly, alongside the advice of the people already caring for you.

A note of caution runs through all of it. Natural does not automatically mean safe, or effective. And the evidence itself is shaped by money. Large cancer trials are expensive, and there is far less reason to fund research into something that cannot be patented, like vitamin C, than into a new drug. That is simply the world we are working in.

I believe more doctors should sit with this research themselves, and that these questions deserve to be debated openly, between conventional, integrative and every other kind of doctor, with the patient at the centre. Saying so out loud can carry a cost. It has for me before, when I raised natural approaches with oncologists, and even writing an article like this carries a risk I have made my peace with. Our duty is to patients, as individuals and as a society, and if we all held onto that, we could discuss and debate every part of this openly, together.

How intravenous vitamin C may affect cancer cells

What draws me to intravenous vitamin C is that, at the right dose, it seems able to tell one kind of cell from another. At the concentrations you can only reach through a vein, vitamin C stops acting as the everyday antioxidant we associate with fruit and begins to behave as a pro-oxidant, which is a very different thing.

Part of the reason lies in how cancer feeds. Many tumours take up far more glucose than the tissue around them, and to do so they cover their surface with extra glucose transporters.6 The oxidised form of vitamin C is shaped enough like glucose to slip through some of those same transporters, a kind of Trojan horse.7

The effect that has been studied most closely, though, happens just outside the cell. At these high concentrations, vitamin C drives the formation of hydrogen peroxide in the fluid bathing the tumour.8, 9 In most tissue that would matter little, but many cancer cells are poorly defended against it. Their antioxidant systems are weaker, and they carry iron that reacts with peroxide in a way healthy cells largely avoid.10, 11

Normally an enzyme called catalase clears that peroxide before it can do harm. Where a cancer cell is short of that protection, its own iron converts the peroxide into hydroxyl radicals, among the most reactive and damaging molecules the body can produce, and the cell is injured from the inside.12

Healthy cells are better protected. They clear peroxide more efficiently and carry less reactive iron, which is why, at these concentrations, pharmacological vitamin C appears to damage cancer cells while largely sparing the normal tissue around them.

What the evidence actually shows

Given intravenously at pharmacological doses, vitamin C reaches blood levels that no tablet can come close to.13

Across the trials done so far, high doses have generally been safe and well tolerated, including alongside some chemotherapy regimens,14–18 radiotherapy in glioblastoma,23 and immunotherapy regimens under active study,20 though whoever gives it still needs to understand the risks I come to next.

Where it seems to earn its place most clearly is in how people feel day to day. It may soften some of the side effects of chemotherapy and help patients get through treatment,19 and it may lift quality of life, less fatigue, less pain, a better appetite and steadier sleep, which makes sense when you remember how often people with cancer are already running low on vitamin C.20

Whether it changes the course of the disease is the harder question, and the honest answer is that we do not yet know. One small randomised trial in metastatic pancreatic cancer found that adding it to chemotherapy went with longer survival, no loss of quality of life and no extra toxicity.21 Another, in advanced prostate cancer, added it to a different chemotherapy and found no benefit.22 From my perspective, the signal is real enough to take seriously.

Is intravenous vitamin C safe? What needs to be checked first?

One of the most important tests before high-dose intravenous vitamin C is a G6PD test.

G6PD stands for glucose-6-phosphate dehydrogenase. It is an enzyme that helps red blood cells generate NADPH, which they need to protect themselves from oxidative stress.24 In someone who is deficient, a high dose of vitamin C can cause the red blood cells to break apart, a reaction called haemolysis.25

This matters even more in Malta because G6PD deficiency is more common in people with Mediterranean, African, Middle Eastern and some Asian backgrounds.24

Kidney function is also important. There are reported cases of acute oxalate nephropathy where very high doses of vitamin C appear to have contributed to serious kidney injury.26

There are also older reports of tumour necrosis, haemorrhage and death following vitamin C treatment, including at doses around 10 grams, where rapid tumour breakdown was considered a possible explanation.27

Other potentially serious problems include vomiting, dehydration from osmotic diuresis, interference with some blood-glucose meters, shifts in electrolytes such as potassium, pain at the infusion site and falls in calcium that may cause tremor.25, 28

This is why I would strongly advise patients to make sure that anyone overseeing their care is fully aware of the potential benefits and risks.

Because this is going directly into your vein, it should be treated like a medication. It is not completely harmless. Proper screening, adequate precautions and clinical judgement matter, just as they would with any IV drip being given to you.

If you have cancer, what should you actually do with all of this?

Saying all of this, if I were to give one piece of advice to a patient with cancer, it would be this: read into and understand all of the options you have.

That may not be easy at all. It can be genuinely difficult, exhausting and frightening. It is also one of the times when people need the most support around them.

I advise patients to ask as many questions as possible, including of me, bring their own reading and sometimes be that annoying patient who wants to understand exactly what is happening. I think this is an approach healthcare professionals should increasingly adopt, where we partner with patients and encourage them to learn as much as they can about the options in front of them, because the more a patient understands, the more meaningfully they can take part in decisions about their care.

One school of thought that can be truly valuable to some patients here is the idea, often associated with Chinese thought, that a crisis is also a turning point. Cancer can feel so threatening that it becomes difficult to see anything beyond the danger, yet adversity can also become a point of real growth, something the research on post-traumatic growth in cancer patients bears out.29 Ayurveda offers another important idea, buddhi, the faculty of intelligence, discernment and intuition that helps us sense what may be right for us.30

And it is not only a matter of mindset. To me, Eastern medicine also offers value in its model of disease. Conventional medicine focuses primarily on identifying and treating the disease, while Eastern medicine also asks what may have weakened the person around it and how that person can be strengthened. I personally do not see these as competing approaches - an integrative outlook I have explored in Ayurveda and the future of medicine. Together, they can give the patient a fuller understanding of what is happening, why it is happening, what in their “terrain” may have contributed to the illness in the first place, and how they can take charge of their own health.

I look at chronic illness, with cancer being one of its clearest examples, as something that can involve the physical, emotional, energetic and spiritual levels of a person. Healing is supported when there is better movement and balance across all of them. This is what I mean when I talk about strengthening the terrain.

Why the terrain matters

The terrain includes diet, physical activity, sleep, physical strength, social support, stress regulation, emotional processing and spiritual wellbeing. These areas can influence cancer risk,31–33 treatment-related symptoms and quality of life,34, 35 and, in some settings, longer-term outcomes.36–39

From my perspective, this is about reducing the burdens the body is carrying, whether nutritional, environmental, physical, emotional, energetic or spiritual. It can mean improving sleep, movement, circulation, strength, support and the body’s ability to produce and use energy well. There are a number of ways to do this and strengthen the terrain, which may include modern lifestyle medicine alongside ancient principles from Ayurveda, Chinese medicine and acupuncture,40–43 mind-body work44–49 and attention to mental and spiritual wellbeing.50, 51

What patients often overlook, but what I have come to see matters most when we are thinking about the whole person, is the importance of helping the body move from prolonged fear and stress, where it becomes harder to rest, recover and function at its best, towards a place of greater safety and support.52–57

This is why I do not think cancer should ever be reduced to vitamin C alone, nor to any other single treatment. To me, care should be integrative and whole-person-oriented.

And yet all of this can become its own kind of weight. One of the worst places to end up is passive, hopeless or paralysed beneath the sheer volume of information.

Statistics are information, not condemnation.

Survival curves are not a single point. There is a tail of people who live longer than the average. Your goal should be to learn from what is known, strengthen the parts that remain within your control, ask the right questions, take an active role in your care, hope for the best and prepare for the worst.

I wish you all the best.

FAQs

Does intravenous vitamin C cure cancer?

No high-quality evidence currently shows that intravenous vitamin C cures cancer as a monotherapy. Beyond that, I do not think this is an easy question for any doctor to answer, because it depends on what someone means by cure. Does cure mean being cancer-free for five years, or for the rest of a person’s life?

I do not find the word especially helpful here. I would rather patients understand what the evidence actually shows, which is the purpose of this article, and place intravenous vitamin C within the wider context of their care.

Why does it have to be intravenous rather than tablets?

The effect depends on reaching blood concentrations that oral vitamin C cannot achieve. Absorption through the gut is tightly controlled, while intravenous administration bypasses that control and can produce pharmacological concentrations in the blood.

Can it be used alongside chemotherapy, radiotherapy or immunotherapy?

Intravenous vitamin C has been studied alongside chemotherapy, radiotherapy and immunotherapy regimens in some trials, as discussed in this article. That does not mean it is appropriate for every person or every regimen. It must be coordinated with your oncology team.

Is high-dose intravenous vitamin C safe?

High-dose intravenous vitamin C should always be considered with proper G6PD screening and medical supervision. G6PD status, kidney function, medications, hydration and the way the infusion is given all need to be considered.

In the wrong person, or if it is given carelessly, it can cause serious harm.

What about other treatments and supplements I have read about?

All of these should be examined for their evidence, safety, indications, interactions and relevance to the person’s case.

However, I believe the more important and often overlooked question for any individual is why their terrain is currently suboptimal. What has contributed to them being in this situation? What may have contributed to the development or progression of the illness? What can be changed safely?

That is the most important question from my perspective.

Where can I get intravenous vitamin C in Malta?

Several clinics in Malta offer vitamin C drips. The most important question is not the address, but how the clinic approaches what it offers you.

Do they understand why you are in the situation you are in? Are they looking at the contributing factors? How are they targeting them? What is their rationale, and do you agree with their approach?

Do your research first.

Is intravenous vitamin C right for me?

It can be, but do your research, ask questions and make sure whoever is overseeing you understands your case.

When these steps are taken properly, I do believe it can offer patients a reasonable source of hope and another option to consider.

Dr Shehan Wijesingha, MD, M.TCM, DipAP, BMedSci, CPT. Vice President, Association of Ayurvedic Professionals UK.

Medical disclaimer: This article is for educational purposes only. It is not medical advice, a diagnosis or a treatment recommendation, and it is not a substitute for care from your own doctors. Intravenous vitamin C in the context of cancer should only be considered alongside conventional oncology care, after appropriate clinical assessment and screening. Do not start, stop or change any cancer treatment based on this article. If your symptoms are new, severe or worsening, contact your GP, oncology team or the appropriate Maltese emergency service.

References
  1. Nobel Prize Outreach (1954). Linus Pauling: Nobel Prize in Chemistry 1954 NobelPrize.org.
  2. Nobel Prize Outreach (1962). Linus Pauling: Nobel Peace Prize 1962 NobelPrize.org.
  3. Cameron E, Pauling L (1976). Supplemental ascorbate in the supportive treatment of cancer: prolongation of survival times in terminal human cancer PNAS.
  4. Creagan ET, Moertel CG, O'Fallon JR, et al. (1979). Failure of high-dose vitamin C therapy to benefit patients with advanced cancer: a controlled trial New England Journal of Medicine.
  5. Moertel CG, Fleming TR, Creagan ET, et al. (1985). High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who had received no prior chemotherapy New England Journal of Medicine.
  6. Vander Heiden MG, Cantley LC, Thompson CB (2009). Understanding the Warburg Effect: the metabolic requirements of cell proliferation Science.
  7. Yun J, Mullarky E, Lu C, et al. (2015). Vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH Science.
  8. Chen Q, Espey MG, Krishna MC, et al. (2005). Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues PNAS.
  9. Chen Q, Espey MG, Sun AY, et al. (2007). Ascorbate in pharmacologic concentrations selectively generates ascorbate radical and hydrogen peroxide in extracellular fluid in vivo PNAS.
  10. Chen Q, Espey MG, Sun AY, et al. (2008). Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumour xenografts in mice PNAS.
  11. Schoenfeld JD, Sibenaller ZA, Mapuskar KA, et al. (2017). O2•− and H2O2-mediated disruption of Fe metabolism causes the differential susceptibility of NSCLC and GBM cancer cells to pharmacological ascorbate Cancer Cell.
  12. Ngo B, Van Riper JM, Cantley LC, Yun J (2019). Targeting cancer vulnerabilities with high-dose vitamin C Nature Reviews Cancer.
  13. Padayatty SJ, Sun H, Wang Y, et al. (2004). Vitamin C pharmacokinetics: implications for oral and intravenous use Annals of Internal Medicine.
  14. NCI PDQ Integrative, Alternative, and Complementary Therapies Editorial Board (2025). Intravenous Vitamin C (PDQ) – Health Professional Version National Cancer Institute (cancer.gov).
  15. Hoffer LJ, Levine M, Assouline S, et al. (2008). Phase I clinical trial of intravenous ascorbic acid in advanced malignancy Annals of Oncology.
  16. Nauman G, Gray JC, Parkinson R, Levine M, Paller CJ (2018). Systematic review of intravenous ascorbate in cancer clinical trials Antioxidants.
  17. Welsh JL, Wagner BA, van't Erve TJ, et al. (2013). Pharmacological ascorbate with gemcitabine for metastatic and node-positive pancreatic cancer Cancer Chemotherapy and Pharmacology.
  18. Monti DA, Mitchell E, Bazzan AJ, et al. (2012). Phase I evaluation of intravenous ascorbic acid with gemcitabine and erlotinib in metastatic pancreatic cancer PLoS ONE.
  19. Ma Y, Chapman J, Levine M, et al. (2014). High-dose parenteral ascorbate enhanced chemosensitivity of ovarian cancer and reduced toxicity of chemotherapy Science Translational Medicine.
  20. Böttger F, Vallés-Martí A, Cahn L, Jimenez CR (2021). High-dose intravenous vitamin C, a promising multi-targeting agent in the treatment of cancer Journal of Experimental & Clinical Cancer Research.
  21. Bodeker KL, Smith BJ, Berg DJ, et al. (2024). A randomized trial of pharmacological ascorbate, gemcitabine, and nab-paclitaxel for metastatic pancreatic cancer Redox Biology.
  22. Paller CJ, Zahurak ML, Mandl A, et al. (2024). High-dose intravenous vitamin C combined with docetaxel in men with metastatic castration-resistant prostate cancer: a randomized placebo-controlled phase II trial Cancer Research Communications.
  23. Allen BG, Bodeker KL, Smith MC, et al. (2019). First-in-human phase 1 clinical trial of pharmacological ascorbate combined with radiation and temozolomide for newly diagnosed glioblastoma Clinical Cancer Research.
  24. Luzzatto L, Ally M, Notaro R (2020). Glucose-6-phosphate dehydrogenase deficiency Blood.
  25. Padayatty SJ, Sun AY, Chen Q, et al. (2010). Vitamin C: intravenous use by complementary and alternative medicine practitioners and adverse effects PLoS ONE.
  26. Wong K, Thomson C, Bailey RR, McDiarmid S, Gardner J (1994). Acute oxalate nephropathy after a massive intravenous dose of vitamin C Australian and New Zealand Journal of Medicine.
  27. Campbell A, Jack T (1979). Acute reactions to mega ascorbic acid therapy in malignant disease Scottish Medical Journal.
  28. Stephenson CM, Levin RD, Spector T, Lis CG (2013). Phase I clinical trial of high-dose intravenous ascorbic acid in patients with advanced cancer Cancer Chemotherapy and Pharmacology.
  29. Gahane V, Deshpande Y, Goyal A (2025). Correlates of post-traumatic growth for patients with breast cancer: a systematic review and meta-analysis Journal of Health Psychology.
  30. Frawley D (Pandit Vamadeva Shastri) (1997). Ayurveda and the Mind: The Healing of Consciousness Lotus Press (book), ISBN 978-0914955368.
  31. World Health Organization (2026). Cancer WHO Fact Sheet.
  32. World Cancer Research Fund and American Institute for Cancer Research (2018). Diet, Nutrition, Physical Activity and Cancer: a Global Perspective Third Expert Report.
  33. McTiernan A, Friedenreich CM, Katzmarzyk PT, et al. (2019). Physical activity in cancer prevention and survival: a systematic review Medicine & Science in Sports & Exercise.
  34. Cramp F, Byron-Daniel J (2012). Exercise for the management of cancer-related fatigue in adults Cochrane Database of Systematic Reviews.
  35. Campbell KL, Winters-Stone KM, Wiskemann J, et al. (2019). Exercise guidelines for cancer survivors: consensus statement from an international multidisciplinary roundtable Medicine & Science in Sports & Exercise.
  36. Kenfield SA, Stampfer MJ, Giovannucci E, Chan JM (2011). Physical activity and survival after prostate cancer diagnosis Journal of Clinical Oncology.
  37. Ornish D, Weidner G, Fair WR, et al. (2005). Intensive lifestyle changes may affect the progression of prostate cancer Journal of Urology.
  38. Kroenke CH, Kubzansky LD, Schernhammer ES, et al. (2006). Social networks, social support, and survival after breast cancer diagnosis Journal of Clinical Oncology.
  39. Courneya KS, Vardy JL, O'Callaghan CJ, et al. (2025). Structured exercise after adjuvant chemotherapy for colon cancer (CHALLENGE) New England Journal of Medicine.
  40. Garcia MK, McQuade J, Haddad R, et al. (2013). Systematic review of acupuncture in cancer care: a synthesis of the evidence Journal of Clinical Oncology.
  41. Ezzo J, Richardson MA, Vickers A, et al. (2006). Acupuncture-point stimulation for chemotherapy-induced nausea or vomiting Cochrane Database of Systematic Reviews.
  42. Crew KD, Capodice JL, Greenlee H, et al. (2010). Randomised, blinded, sham-controlled trial of acupuncture for aromatase inhibitor-associated joint symptoms Journal of Clinical Oncology.
  43. Walker EM, Rodriguez AI, Kohn B, et al. (2010). Acupuncture versus venlafaxine for vasomotor symptoms in patients with hormone receptor-positive breast cancer Journal of Clinical Oncology.
  44. Mustian KM, Sprod LK, Janelsins M, et al. (2013). Multicentre randomised controlled trial of yoga for sleep quality among cancer survivors Journal of Clinical Oncology.
  45. Garland SN, Carlson LE, Stephens AJ, et al. (2014). Mindfulness-based stress reduction compared with cognitive behavioural therapy for insomnia comorbid with cancer Journal of Clinical Oncology.
  46. Piet J, Würtzen H, Zachariae R (2012). The effect of mindfulness-based therapy on symptoms of anxiety and depression in adult cancer patients and survivors Journal of Consulting and Clinical Psychology.
  47. Oh B, Butow P, Mullan B, et al. (2010). Impact of medical Qigong on quality of life, fatigue, mood and inflammation in cancer patients Annals of Oncology.
  48. Wayne PM, Lee MS, Novakowski J, et al. (2018). Tai Chi and Qigong for cancer-related symptoms and quality of life: a systematic review and meta-analysis Journal of Cancer Survivorship.
  49. Mao JJ, Ismaila N, Bao T, et al. (2022). Integrative medicine for pain management in oncology: Society for Integrative Oncology–ASCO guideline Journal of Clinical Oncology.
  50. Greenlee H, DuPont-Reyes MJ, Balneaves LG, et al. (2017). Clinical practice guidelines on the evidence-based use of integrative therapies during and after breast cancer treatment CA: A Cancer Journal for Clinicians.
  51. Hulett JM, Armer JM (2016). A systematic review of spiritually based interventions and psychoneuroimmunological outcomes in breast cancer survivorship Integrative Cancer Therapies.
  52. Reiche EMV, Nunes SOV, Morimoto HK (2004). Stress, depression, the immune system, and cancer The Lancet Oncology.
  53. Thaker PH, Han LY, Kamat AA, et al. (2006). Chronic stress promotes tumour growth and angiogenesis in a mouse model of ovarian carcinoma Nature Medicine.
  54. Ben-Eliyahu S, Yirmiya R, Liebeskind JC, et al. (1991). Stress increases metastatic spread of a mammary tumour in rats: evidence for mediation by the immune system Brain, Behavior, and Immunity.
  55. Pace TWW, Mletzko TC, Alagbe O, et al. (2006). Increased stress-induced inflammatory responses in male patients with major depression and increased early life stress American Journal of Psychiatry.
  56. Parker PA, Pettaway CA, Babaian RJ, et al. (2009). The effects of a presurgical stress-management intervention for men with prostate cancer undergoing radical prostatectomy Journal of Clinical Oncology.
  57. Cohen L, Parker PA, Vence L, et al. (2011). Presurgical stress management improves postoperative immune function in men with prostate cancer undergoing radical prostatectomy Psychosomatic Medicine.