A Report From a Doctor Who Treats Cancer With IV Vitamin C

High Dose Vitamin C for Cancer
The Struggle with “Non-Evidence-Based” Medical Practice
by Dr. Raymond CF Yuen

OMNS (Sept. 29, 2021) While serving as a consultant for a cancer support group, I was often asked how diet, nutrition or supplements can help cancer patients. Eventually, I searched and found that many vitamins and micronutrients are clinically helpful in improving quality of life and prolonging patient survival. I began to explore the use of non-toxic medicines or nutrients to help prevent and reverse cancer, and one of the star products I found was vitamin C. I applied high dose intravenous vitamin C (HDIVC) combined with other micronutrients and supplements to help patients. Amazingly, but not surprisingly, many of them improved. To spread the word to the medical world, I published a report on some case histories. [1] The report drew some attention and many criticisms about the vitamin C treatment. What puzzled me was that the opposing views were mainly from medical professionals. They criticized the HDIVC treatment as non-evidence-based and unlawful. I rechecked the medical literature and clinical research on vitamin C and noted that the controversy had been there since Captain James Lind used citrus fruits to treat his sailors, and more recently, Linus Pauling and Cameron used HDIVC in their cancer trials. [2]

Although HDIVC as a cancer treatment therapy has not been well documented, it is well supported and recognized as a supportive or adjunct cancer treatment. [3-7] HDIVC has proven effective in reducing complications from chemotherapy [8] and radiotherapy. [9] It also enhances the killing of cancer cells [10,11] which improves patients’ quality of life and survival. [8,12] Recent findings have documented that HDIVC enhances immunotherapy and reduces its adverse side effects. [13,14]

The more I researched vitamin C and its clinical application, the more I realized it is a panacea for medicine. [15] How could a trained physician miss out on this potential cure for most inflammatory diseases, including cancer, cardiovascular disease, and infectious diseases such as Covid-19?

I am convinced HDIVC only appears to be a controversial treatment for those unaware of recent research on essential nutrients — and who have a potential conflict of interest. [2,16] Despite my struggle to convince the medical establishment of its clinical utility, HDIVC is crucial for cancer treatment. [1,17,18] I hope my work on vitamin C research will help clarify some of the medical myths about HDIVC therapy and its clinical application in cancer immunotherapy. [2,3,19] Knowledge about vitamin C saves lives.

Malaysia, Indonesia, and Singapore are relatively strict about the use of alternative medicine such as HDIVC for cancer and other chronic diseases. HDIVC is classified as non-evidence-based medical practice, and doctors utilizing it are threatened with being censored and penalized. Yet, somehow, many physicians and specialists quietly provide HDIVC for their patients and relatives or even for their politicians. In contrast, countries like the Philippines, Taiwan, and Thailand are quite open to HDIVC, and every year draws more medical tourists. Hong Kong is more flexible in alternative medical treatment, and some clinics there offer HDIVC as supportive care for cancer with special permission granted by the medical authority. I hope recent research will produce more clinical data to “certify” that HDIVC is beneficial for treating cancer.

However, time is running out for some cancer patients. An immediate application of HDIVC could be life-saving for them. Even though the medical establishment does not accept the efficacy of HDIVC, given its safety profile and potential benefits in cancer treatment, HDIVC may be given on the grounds of compassionate use. Even for the advanced stages of cancer, HDIVC has proven effective in reducing inflammation and improving quality of life. [20,21]

In the ten years that I have been administering HDIVC for cancer patients, I have always found it effective in improving patients’ quality of life and survival. I have seen stage 4 cancer patients who were given a poor prognosis survive longer than their oncologists’ prediction or expectation. I have documented a stage 4 ovarian cancer patient who survived more than five years. [17] Now for over eight years, she is still asymptomatic, cancer-free, and has a good quality of life.

Recent research has shown that while chemotherapy kills cancer, it also tends to enhance the spread of cancer throughout the body [22], and most cancer patients given chemotherapy eventually develop side effects or other organ failures. [22] Another common phenomenon is the off-label use of chemotherapeutic drugs for cancer patients, which according to one study often accounts for more than half of adult cancer treatments. [23] In another study, 33% to 65% of end-stage cancer patients were more likely to be given such off-label drugs. Eaton et al. reported that 82% of end-stage breast cancer patients take off-label chemotherapy. [24] The US National Cancer Institute has stated that the actual figure of off-label cancer drugs might be even higher than reported. [25]

This off-label chemotherapy is non-evidence-based and often has significantly higher side effects and reduces patients’ quality of life. We have proposed the off-label use of HDIVC for cancer, [26] because it is much safer with good patient outcomes. HDIVC is more body-friendly and can even enhance immune functions to help neutralize cancer. [19] For these very desperate cancer patients, treatments that are not focused solely on killing cancer cells may be preferred. HDIVC treatment may control the tumor growth while improving quality of life and lengthening survival periods. [7,16]

Notably, high dose vitamin C has been used for the last 5 decades either as supportive care or as an anti-cancer treatment [27] with anecdotal successes coupled with very good safety profiles. [18,28] Nevertheless, so far, it has failed to achieve any regulatory approval. Fortunately, the various vitamin C mechanisms that control cancers are now much better documented, and there are currently many ongoing clinical trials. [11,29,30] With the currently better known high dose vitamin C pharmaco-kinetics and anti-cancer mechanisms, [31-33] it is recommended that all cancer patients should be considered on compassionate grounds to receive high dose vitamin C as supportive treatment or as an adjunct anti-cancer therapy. [7,11]

Regulations apart, for a desperate patient without realistic treatment modalities, the patient’s therapeutic response should be our guiding principle — rather than continuing to adhere to strict treatment guidelines. This is especially true in the treatment of advanced cancers, for such cancers may involve a multiplicity of organs, and the involvement of each organ may also differ. Thus, the treatment of choice should be more precise and personalized.

In contrast to the official rulings alluded to above, high dose vitamin C may be considered as an innovative cancer treatment that fulfills most of these requirements:

There is clinical plausibility [34,35]
There is biological plausibility [5,11,32]
There is proven clinical effectiveness [36]
It is affordable to most desperate cancer patients [5,18]
It may enhance the effects of regimens [14,37,38] (therapy-related)
It may repair the damage, e.g., vocal cord recovery [39] (disease-related)
It may eradicate cancer stem cells [4,10,40,41]

Recent well-documented research shows that high dose vitamin C therapy has several biological mechanisms of action on cancer cells. [6,11,35] This is undoubtedly the rationale for its strong history of clinical success in treating cancers. [42] However, the clinical efficacy remains controversial since the gold standard for an investigational drug would be to conduct randomized controlled trials — which is difficult without patent benefits for vitamin C. Apparently, with limited funding, one has to work much harder on vitamin C research. Reassuringly, there is growing evidence supporting the anti-cancer effects of high dose vitamin C, especially as recent research suggests that vitamin C is well tolerated and has minimal side effects. [29,43] Recently, there have been a few ongoing randomized and non-randomized clinical trials of high dose vitamin C on cancer. [29,30,44] As of 2018, the cancer researchers at the Holden Comprehensive Cancer Centre of the University of Iowa have received a five-year grant of $9.7 million from the US National Cancer Institute for high dose vitamin C cancer research. [44] Undoubtedly, more and more high dose vitamin C clinical research activities are to be undertaken soon. One of the reasons is, although cancer treatment resistance is closely related to cancer stem cells, vitamin C may be able to eradicate these stubborn cancer stem cells. [10,40,41,45] Meanwhile, with the safety profile and clinical effectiveness of vitamin C, it would be advisable to commence high dose vitamin C on compassionate grounds for desperate cancer patients. [12,46,47]

At this period of severe economic depression, COVID-19 pandemic, HDIVC is attractive as it not only has a good safety profile but is also eminently affordable. Moreover, as no exceedingly expensive, very time-consuming drug development efforts are required, HDIVC would seem more crucial than controversial.

(Yuen Chuen Fong Raymond, MBBS, M Med Sc, M Med, is Physician in Charge, Hosanna Clinic, Singapore. He practices family medicine and specializes in occupational medicine with interest in cancer prevention and medical nutrition. Dr. Yuen frequently gives lectures on cancer prevention and is the author of the Chinese cancer prevention book Passover Cancer, a layman’s guide on the management of cancer with diet and nutrition. His publication list follows.)


Effects of High Dose Vitamin C for Cancer Patients — Nine Cases [1]
Vitamin C – The Remarkable Story of Controversy [2]
The Missing Link In Cancer Treatment: High Dose Vitamin C [3]
High Dose Intravenous Vitamin C and Radiotherapy Reversing Vocal Cord Palsy Caused by Lung Cancer: A Case Report [9]
High Dose Vitamin C helps prevent recurrence of Stage IV Ovarian Cancer. A case report [17]
Embracing cancer immunotherapy with vital micronutrients [19]
Off-Label Cancer Prescription: A Paradox to Evidence-Based Medicine [26]


[1] Yuen RCF, Glenda CSL, Meng LK. (2016) Effects of High Doses of Vitamin C on Cancer Patients in Singapore: Nine Cases. Integr Cancer Ther 15:197-204. https://pubmed.ncbi.nlm.nih.gov/26679971

[2] Yuen RCF. (2021) Vitamin C – The Remarkable Story of Controversy. In: Shiu Y Tsao, ed. Bridging the Gap: In This Era of Cancer Immunotherapy, Nova Medicine and Health, Oncology; 2021, p. 59-99. ISBN: 9781536199000

[3] Yuen RCF. (2021) The Missing Link In Cancer Treatment: High Dose Vitamin C. In: Tsao SY, ed. Bridging the Gap: In This Era of Cancer Immunotherapy, Nova Medicine and Health, Oncology; 2021, p. 101-186.

[4] Lv H, Wang C, Fang T, et al. (2018) Vitamin C preferentially kills cancer stem cells in hepatocellular carcinoma via SVCT-2. NPJ Precis Oncol 2:1. https://pubmed.ncbi.nlm.nih.gov/29872720

[5] Mastrangelo M, Massai L, Fioritoni G, Lo Coco F. (2017) Vitamin C Against Cancer, InTech. https://doi.org/10.5772/intechopen.68746

[6] Vissers MCMM, Das AB. (2018) Potential Mechanisms of Action for Vitamin C in Cancer: Reviewing the Evidence. Front Physiol 9:809. https://pubmed.ncbi.nlm.nih.gov/30018566

[7] Klimant E, Wright H, Rubin D, Seely D, Markman M. (2018) Intravenous vitamin C in the supportive care of cancer patients: a review and rational approach. Curr Oncol 25:139-148. https://pubmed.ncbi.nlm.nih.gov/29719430

[8] Vollbracht C, Schneider B, Leendert V, et al. (2011) Intravenous vitamin C administration improves quality of life in breast cancer patients during chemo-/radiotherapy and aftercare: results of a retrospective, multicentre, epidemiological cohort study in Germany. In Vivo 25:983-990. https://pubmed.ncbi.nlm.nih.gov/22021693

[9] Yuen RCF, Tsao SY. (2021) High Dose Intravenous Vitamin C and Radiotherapy Reversing Vocal Cord Palsy Caused by Lung Cancer: A Case Report. In: Bridging the Gap: In This Era of Cancer Immunotherapy, Nova Medicine and Health, Oncology; 2021, p. 180-186.

[10] Satheesh NJ, Samuel SM, BÜsselberg D. (2020) Combination therapy with vitamin C could eradicate cancer stem cells. Biomolecules 10:79. https://pubmed.ncbi.nlm.nih.gov/31947879.

[11] Ngo B, VanRiper JM, Cantley LC, Yun J. (2019) Targeting cancer vulnerabilities with high-dose vitamin C. Nat Rev Cancer 19:271-282. https://pubmed.ncbi.nlm.nih.gov/30967651.

[12] Carr AC, Vissers MCM, Cook J. (2014) Parenteral vitamin C for palliative care of terminal cancer patients. NZ Med J 127:84-86. https://pubmed.ncbi.nlm.nih.gov/24997468

[13] Shiu Y Tsao. (2021) Bridging the Gap: In This Era of Cancer Immunotherapy. Nova Medicine and Health, Oncology; 2021.

[14] Magrí A, Germano G, Lorenzato A, et al. (2020) High-dose vitamin C enhances cancer immunotherapy. Sci Transl Med 12:eaay8707. https://pubmed.ncbi.nlm.nih.gov/32102933.

[15] Levy TE. (2011) Primal Panacea. MedFox Pub. ISBN-13?: ? 978-0983772804

[16] Carr AC, Cook J. (2018) Intravenous Vitamin C for Cancer Therapy – Identifying the Current Gaps in Our Knowledge. Front Physiol 9:1182. https://pubmed.ncbi.nlm.nih.gov/30190680

[17] Yuen RCF, Stephanie LA, Tin Wei Y. (2018) High-Dose Vitamin C Helps Prevent Recurrence of Stage IV Ovarian Cancer: A Case Report. J Orthomol Med 2018;33:4. https://isom.ca/article/high-dose-vitamin-c-helps-prevent-recurrence-stage-iv-ovarian-cancer-case-report

[18] Cantley L, Yun J. (2020) Intravenous High-Dose Vitamin C in Cancer Therapy – National Cancer Institute. Natl Cancer Inst. https://www.cancer.gov/research/key-initiatives/ras/ras-central/blog/2020/yun-cantley-vitamin-c

[19] Yuen RCF, Tsao S. (2021) Embracing cancer immunotherapy with vital micronutrients. World J Clin Oncol 12:712-724. https://doi.org/10.5306/wjco.v12.i9.712

[20] Yeom CH, Jung GC, Song KJ. (2007) Changes of terminal cancer patients’ health-related quality of life after high dose vitamin C administration. J Korean Med Sci 22:7-11. https://pubmed.ncbi.nlm.nih.gov/17297243

[21] Zasowska-Nowak A, Nowak PJ, Cialkowska-Rysz A. (2021) High-Dose Vitamin C in Advanced-Stage Cancer Patients. Nutrients 13:735. https://pubmed.ncbi.nlm.nih.gov/33652579

[22] Schirrmacher V. (2019) From chemotherapy to biological therapy: A review of novel concepts to reduce the side effects of systemic cancer treatment (Review). Int J Oncol 54:407-419. https://pubmed.ncbi.nlm.nih.gov/30570109

[23] Saiyed MM, Ong PS, Chew L. (2017) Off-label drug use in oncology: a systematic review of literature. J Clin Pharm Ther 42:251-258. https://pubmed.ncbi.nlm.nih.gov/28164359

[24] Eaton AA, Sima CS, Panageas KS. (2016) Prevalence and Safety of Off-Label Use of Chemotherapeutic Agents in Older Patients With Breast Cancer: Estimates From SEER-Medicare Data. J Natl Compr Cancer Netw 14:57-65. https://pubmed.ncbi.nlm.nih.gov/26733555

[25] US National Cancer Institute. Off-Label Drug Use in Cancer. https://www.cancer.gov/about-cancer/treatment/drugs/off-label

[26] Shien MHY, Yuen RCF. (2019) Off -Label Cancer Prescription: A Paradox to Evidence-Based Medicine. J Orthomol Med 34:1-23. https://isom.ca/article/off-label-cancer-prescription-a-paradox-to-evidence-based-medicine

[27] Cameron E, Campbell A. (1974) The orthomolecular treatment of cancer II. Clinical trial of high-dose ascorbic acid supplements in advanced human cancer. Chem Biol Interact 9:285-315. https://pubmed.ncbi.nlm.nih.gov/4430016

[28] Prier M, Carr A, Baillie N. (2018) No Reported Renal Stones with Intravenous Vitamin C Administration: A Prospective Case Series Study. Antioxidants 7:68. https://pubmed.ncbi.nlm.nih.gov/29883396

[29] Nauman G, Gray J, Parkinson R, Levine M, Paller C. (2018) Systematic Review of Intravenous Ascorbate in Cancer Clinical Trials. Antioxidants 7:89. https://pubmed.ncbi.nlm.nih.gov/30002308

[30] US National Cancer Institute. Clinical Trials Using Ascorbic Acid https://www.cancer.gov/about-cancer/treatment/clinical-trials/intervention/ascorbic-acid

[31] Kazmierczak-Baranska J, Boguszewska K, Adamus-Grabicka A, Karwowski BT. (2020) Two faces of vitamin c-antioxidative and pro-oxidative agent. Nutrients 2020;12:1501. https://pubmed.ncbi.nlm.nih.gov/32455696

[32] Roa FJ, Peña E, Gatica M, et al. (2020) Therapeutic Use of Vitamin C in Cancer: Physiological Considerations. Front Pharmacol 11:211. https://pubmed.ncbi.nlm.nih.gov/32194425

[33] Pawlowska E, Szczepanska J, Blasiak J. (2019) Pro- and Antioxidant Effects of Vitamin C in Cancer in Correspondence to Its Dietary and Pharmacological Concentrations. Oxid Med Cell Longev 2019:7286737. https://pubmed.ncbi.nlm.nih.gov/31934267

[34] Wilson MK, Baguley BC, et al. (2014) Review of high-dose intravenous vitamin C as an anticancer agent. Asia Pac J Clin Oncol 10:22-37. https://pubmed.ncbi.nlm.nih.gov/24571058

[35] Bakalova R, Zhelev Z, Miller T, Aoki I, Higashi T. (2020) New potential biomarker for stratification of patients for pharmacological vitamin C in adjuvant settings of cancer therapy. Redox Biol 28:101357. https://pubmed.ncbi.nlm.nih.gov/31678721

[36] Krzyszczyk P, Acevedo A, Davidoff EJ, et al. (2018) The growing role of precision and personalized medicine for cancer treatment. Technol (Singap World Sci) 6:79-100. https://pubmed.ncbi.nlm.nih.gov/30713991

[37] Liu F, Zhu Y, Zhang J, Li Y, Peng Z. (2020) Intravenous high-dose vitamin C for the treatment of severe COVID-19: study protocol for a multicentre randomised controlled trial. BMJ Open 10:e039519. https://pubmed.ncbi.nlm.nih.gov/32641343

[38] Boretti A, Banik BK. Intravenous vitamin C for reduction of cytokines storm in acute respiratory distress syndrome. PharmaNutrition 2020;12:100190. https://pubmed.ncbi.nlm.nih.gov/32322486

[39] Yuen RCF, Tsao S. (2021) High dose intravenous vitamin C and Radiotherapy reversing vocal cord palsy caused by lung cancer: a case report. In: Bridging the Gap: In This Era of Cancer Immunotherapy, Nova Medicine and Health, Oncology; 2021, p. 180-6.

[40] Cimmino L, Neel BG, Aifantis I. (2018) Vitamin C in Stem Cell Reprogramming and Cancer. Trends Cell Biol 28:698-708. https://pubmed.ncbi.nlm.nih.gov/29724526

[41] Kim TJ, Byun JS, Kwon HS, Kim DY. (2018) Cellular toxicity driven by high-dose vitamin C on normal and cancer stem cells. Biochem Biophys Res Commun 497:347-53. https://pubmed.ncbi.nlm.nih.gov/29432735

[42] Cameron E, Pauling L. (1976) Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci USA 73:3685-3689. https://pubmed.ncbi.nlm.nih.gov/1068480

[43] ScienceDaily. (2017) High Doses of Vitamin C to Improve Cancer Treatment Passes Human Safety Trial. https://www.sciencedaily.com/releases/2017/03/170330142341.htm

[44] Carver College of Medicine, University of Iowa Health Care. Grant will fund cancer clinical trials to test high-dose vitamin C. https://medicine.uiowa.edu/content/grant-will-fund-cancer-clinical-trials-test-high-dose-vitamin-c

[45] DeFrancesco EM, Bonuccelli G, Maggiolini M, Sotgia F, Lisanti MP. (2017) Vitamin C and Doxycycline: A synthetic lethal combination therapy targeting metabolic flexibility in cancer stem cells (CSCs). Oncotarget 8:67269-67286. https://pubmed.ncbi.nlm.nih.gov/28978032

[46] Carr AC, McCall C. (2017) The role of vitamin C in the treatment of pain: new insights. J Transl Med 15:77. https://pubmed.ncbi.nlm.nih.gov/28410599

[47] Carr AC, Vissers MCM, Cook JS. (2014) The Effect of Intravenous Vitamin C on Cancer- and Chemotherapy-Related Fatigue and Quality of Life. Front Oncol 4:283. https://pubmed.ncbi.nlm.nih.gov/25360419

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Update Oct 12, 2021

We report with great sadness Dr. Raymond Yuen’s passing today:
Dr. Raymond Yuen was ‘a different type of doctor’, patients say