Intravenous Vitamin C for Cancer Treatment in Pets

Vitamin C (also known as ascorbic acid) is a micronutrient found in many foods. Interestingly, it is essential for primates and guinea pigs, but not for any other mammals since most species can manufacture it from other substances in their diets. The discovery that the disease scurvy, common throughout history among sailors and others without access to fresh fruits and vegetables for long periods, was due to Vitamin C deficiency is one of the classic examples of early use of science and scientific methods to solve a serious health problem. Ensuring adequate Vitamin C intake has been one of the most effective public health measures in history.

However, in the 1970s the notion began to gain popularity that extremely high doses of Vitamin C, well beyond any nutritional requirements, could be used as a drug to prevent or treat disease. This was largely due to the efforts of Nobel Laureate Linus Pauling, a brilliant chemist who developed a bit of an obsession with the medicinal use of Vitamin C in his later years. Because of this, he is considered the paragon of the Nobel Disease, in which an accomplished scientist becomes enamored of implausible or pseudoscientific ideas and refuses to abandon them when the evidence dictates they should. Though the verdict is not etched in stone on all aspects of the medicinal use of megadoses of Vitamin C, but as we will see it is clear that Pauling suffered from the Nobel Disease with respect to this practice.

The two primary uses to which Pauling, and many others in his time and since, have suggest Vitamin C could be put are in the prevention and treatment of the common cold and cancer. In terms of the common cold, the evidence indicates there is no benefit for prevention and there might or might not be a small, largely clinically irrelevant benefit for treatment. Pauling was unquestionably wrong on this one. The situation is more complex with regard to cancer therapy.

Does It Work?
The initial studies of Vitamin C as a cancer therapy, reported by Pauling and Dr. Ewan Cameron, appeared to show a benefit in terms of survival when cancer patients received large doses of Vitamin C along with standard therapy. However, these were methodologically terrible studies that were likely only accepted for publication on the basis of Pauling’s prestige. Subsequent research by others replicating this work (e.g. 1, 2) did not find any benefit. A nice review of this history is available on the Science-Based Medicine Blog.

One objection to the negative studies offered by proponents of Vitamin C as a cancer therapy was that they primarily gave the vitamin orally. There is some in vitro and lab animal evidence (e.g. 3, 4) suggesting Vitamin C is more toxic to cancer cells than healthy cells at very high doses (though, of course, there are some limitations to these studies). The concentrations associated with this effect can only be achieved in living animals with intravenous injection of high doses of Vitamin C, so some have argued that the studies showing no benefit from oral use should be re-evaluated with intravenous dosing.

There is little clinical research in humans, and none in companion animals, to show that intravenous high-dose Vitamin C is beneficial for cancer patients.  Some small scale uncontrolled studies and case reports have shown some potential effects, but it is unclear if there is any meaningful benefit in terms of survival, quality of life, and other clinically important variables. A narrative review from 2010 concludes:

In view of this lack of data after trials which have included at least 1,591 patients over 33 years, we have to conclude that we still do not know whether Vitamin C has any clinically significant antitumor activity. Nor do we know which histological types of cancers, if any, are susceptible to this agent. Finally, we don’t know what the recommended dose of Vitamin C is, if there is indeed such a dose, that can produce an anti-tumor response.

Similarly, the American Cancer Society position on Vitamin C in cancer patients states,

Although high doses of vitamin C have been suggested as a cancer treatment, the available evidence from clinical trials has not shown any benefit.

And while it is easy, as always, to find supportive anecdotes, it is also easy to find anecdotes that show no benefit. I’ve discussed previously why such anecdotes are only useful in suggesting, not proving, hypotheses. Unfortunately, anecdotal evidence is a bit like a two-headed coin in that proponents of any practice win no matter which side is showing. If a patient seems to improve, that is claimed to demonstrate the therapy works. If a patient doesn’t improve, however, that doesn’t indicate that the therapy doesn’t work in general, only that it doesn’t work in all patients. Since nothing is perfect, this sounds reasonable until you realize that with this kind of spin anecdotes can only ever be used to support a therapy, never to challenge it.

The most positive possible spin one can put on the evidence in humans and lab animals is that there might be a small benefit in some cases, though it is more likely this is simply random noise in the data produced by a small number of studies with significant limitations. No spin at all can be put on the evidence for intravenous Vitamin C in companion animals because there is none, apart from the inevitable anecdotes, of course. One study has shown intravenous Vitamin C generates high levels of the chemical in dogs for only a very short time, so any beenfits would either have to happen from only a brief period of exposure or many injections would have to be given frequently to have any effect.

Is It Safe?
I have always argued that any therapy which has a benefit will undoubtedly have side effects. Living organisms are simply too complex to tinker with their workings and not have unintended, as well as desirable, effects. Though its benefits are still unproven, there is no doubt megadoses of Vitamin C have real physiological effects, and so there is the possibility for harm as well as benefits.

Some research conducted about the same time as Pauling’s studies has suggested that dietary Vitamin C can accelerate the growth of some cancers in laboratory mice. Minor side effects are commonly reported, including nausea, diarrhea, and changes in blood pressure and blood sugar.

And high doses of Vitamin C given intravenously have been documented to cause kidney failure, so it should not be used in patients with any compromise in kidney function. Formation of kidney stones has also been linked to Vitamin C supplementation. Individuals with certain enzyme deficiencies or abnormalities of iron absorption can also be harmed by excessive Vitamin C supplementation. A particularly significant issue in cancer patients is that Vitamin C has been shown to reduce the effectiveness of some anti-cancer drugs. Using a chemical with unproven value that can interfere with the proven benefits of medication in patients with a serious disease is not smart or compassionate care.

Once again, there doesn’t appear to be any formal scientific research on the safety of high doses of intravenous Vitamin C in companion animals. Using such a therapy is a bit like throwing darts blind-folded and hoping to hit the bull’s eye rather than the person standing next to the target.

Bottom Line
High doses of Vitamin C given by intravenous injection have not been proven to have any benefit in human cancer patients. There are some studies suggesting such a benefit might exist, but the evidence is weak and contradictory. There is also evidence of both minor and serious side effects associated with this treatment. Vitamin C can interfere with some chemotherapy drugs, thus reducing the benefits of conventional therapy. And, as always, there is a serious risk of harm for patients who elect this unproven therapy over better studied treatments with known risks and benefits.

There is no published clinical research in companion animals evaluating the effects of intravenous Vitamin C as a cancer therapy. The safety and efficacy of this practice is completely unknown despite claims made based on uncontrolled anecdotes and extrapolation from studies in humans.

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24 Responses to Intravenous Vitamin C for Cancer Treatment in Pets

  1. Kle says:


    Thanks for this article!
    My dog was diagnosed with hemangiosarcoma on his leg and amputated. Now he is under chemo doxorubicin and I was giving him these two supplements:

    Am doing wrong then?

  2. skeptvet says:

    The problem is that for most of the ingredients in those supplements, no one knows if they are beneficial, harmful, or neutral. Glycosamine will almost certainly do nothing. The fish oil might have some benfits. And there is some evidence that Vitamins C can reduce the effectiveness of chemotherapy (see the section Vitamins and Supplements in this post for a list of articles ont he risks of vitamins). So while I understand the desire to do everything you can to help your pet, the reality is that without proper scientific study, there is no way to predict the effect of adding things like this to his treatment, and it is as easy to make things worse as better.

    Good luck!

  3. A D says:

    Your comments at Bottom Line are the most eregreious lies about the efficacy of IV vitamin C I have ever heard. You are either an ostrich or blind as a bat since there are thousands of cases where vitamin C has prevented, cured and even reversed many illnesses.
    If you are capable of reading and comprehending simple English, I suggest you read
    “Primal Panacea” and “Curing the Incurable” by Thomas E. Levy MD, JD. Dr Levy is a Board Certified Cardiologist and Internest and has treated many with vitamin C and obtained miraculous results. Irresponsible statements by an uninformed layman like yourself borders on criminality by espousing falsehoods about a treatment that may benefit someone reading your misinformation about vitamin C.

  4. skeptvet says:

    The arrogance you display in assuming anyone who disagrees with you is either lying or ignorant is astounding. And yet, despite your vehemence, you offer no evidence of any kind, much less reliable scientific research findings, to support your beliefs. Referring people to someone else’s opinions doesn’t constitute a substantive argument, especially since Dr. Levy himself is not a reliable source of truly scientific information. Sorry if the facts disturb you, but believing doesn’t make things so.

  5. fluidtherapy says:

    @ AD

    Egregious lies? As opposed to really good lies? Excellent diatribe. If you’re simplistic enough to fall for the hoodwinking of one Dr. Levy, you’ll love the insight provided by one Dr. Oz on weight loss, toxin cleansing and boosting immunity. Can’t wait ’till we can meet and talk at the next Nobel Prize awards ceremony (I understand Linus Pauling will be there this year!)

    Ciao, FT

  6. Kim says:

    The vitamin C treatment works. There a plenty of studies done on it, but why take the word of some studies. While your blog is intended for animals, my proof is with a human, that human being my mom. She was diagnosed with breast cancer, and under went only this treatment after having MOST of her tumor removed, one month later after three separate doctors reading her new X-rays, they all agreed that her cancer was gone. I don’t know if this is an across the board thing, but that is proof that it should be taken seriously.

  7. skeptvet says:

    I’m glad your mother is well, but anecdotes like these should not be taken seriously. They exist for every medical treatment ever invented as well as for psychic phenomena, astrology, alien abduction, and pretty much any claim anybody has ever made. If we rely on anecdotes to prove claims, then everything has to be true. We tried that for thousands of years before the scientific approach was developed, and we never had anything even approaching the success at treating disease we have had since.

  8. Pingback: Evidence Concerning Vitamin and Mineral Supplements- Safety and Efficacy | The SkeptVet Blog

  9. Werner Ulrich says:

    I am a Vet, working in Spain, since 1975. Cancer is one of our most common disease today in the clinic, 20 years ago we had only a few cases every month. If chemo does not work we always have to euthanize. We always say in the clinic that the medicine with the worst secondary effect is the one we use to euthanize, therefore we try other treatment options. I use i.v.vitamin C (sodium ascorbate) very often with fantastic results with the the Riordan i.v. protocol and the nutritional supplements recommended by the Dr.Rath foundation (
    Its ease to use and inexpensive. It works.

  10. skeptvet says:

    Sorry, but “It works” is not a justified conclusion in the absence of supporting research evidence. In the case of vitamin C, there has been a great deal of research and it has failed to show clinically meaningful benefits.

  11. Werner Ulrich says:

    When I say “it works” I speak about my personal experience only.
    I did not believe in it 10 years ago, sincerely. We had to euthanize a lot of dogs and cats using the standard protocols and this was the reason just to try another treatment options, not only vitamin C.

  12. Frankie says:

    Your report is written without any knowledge about the latest Ascorbic Acid IV trials. What are you trying to accomplish with your story? Ascorbic Acid IV is once again the proof that cancer is curable for a very affordable price. Don’t scare people. It works. There is even proof for pancreatic cancer. The tumor declined by 50%.

  13. skeptvet says:

    The post was pretty well-researched, but if I’ve missed some good clinical trials feel free to post links and the results here. Claoims without evidence don’t advance our understanding at all.

  14. Michaela says:

    Thanks for great article. I want to ask anyone here who has experiences with vit C…what dosage did you use? I mean a dosage per libra (or kilogram). How often, one a week or twice a week? An finally, what is amount of 0,9% sodium chloride for dilution? Please, help me, I want to start with it for “treatment” of osteosarcoma for my dog as soon as possible. Thanks a lot!

  15. jvburke says:

    Anecdotal evidence is not evidence.
    But it is not proof of no success, either.
    So all the people who say they have witnessed the success are not in themselves evidence of effectiveness and to dismiss them as not a scientific study is correct in the academic sense as they are a data point in an uncontrolled study – BUT – they must be considered as a stimulant to research more.

    Having said that …
    here is
    note this article from National Cancer Institute – NIH

    “…Have any clinical trials (research studies with people) of high-dose vitamin C been conducted?
    Several studies of high-dose vitamin C in patients with cancer have been done in recent years, including the following:

    Studies of vitamin C alone

    •Intravenous (IV) vitamin C was studied in patients with breast cancer who were treated with adjuvant chemotherapy and radiation therapy. The study found that patients who received IV vitamin C had better quality of life and fewer side effects than those who did not.

    •A study of IV vitamin C and high doses of vitamin C taken by mouth was done in patients with cancer that could not be cured. Vitamin C was shown to be a safe and effective therapy to improve quality of life in these patients, including physical, mental, and emotional functions, symptoms of fatigue, nausea and vomiting, pain, and appetite loss.

    •Vitamin C has been shown to be safe when given to healthy volunteers and cancer patients at doses up to 1.5 g/kg, while screening out patients with certain risk factors who should avoid vitamin C. Studies have also shown that Vitamin C levels in the blood are higher when taken by IV than when taken by mouth, and last for more than 4 hours.

    Studies of vitamin C combined with other drugs

    Studies of vitamin C combined with other drugs have shown mixed results:

    •In a small study of 14 patients with advanced pancreatic cancer, IV vitamin C was given along with chemotherapy and treatment with a targeted therapy. Patients had very few bad side effects from the vitamin C treatment. The nine patients who completed the treatment had stable disease as shown by imaging studies.

    •In another small study of 9 patients with advanced pancreatic cancer, patients were given chemotherapy in treatment cycles of once per week for 3 weeks along with IV vitamin C twice per week for 4 weeks. These patients had disease that did not progress for a period of months. The combined treatment was well tolerated and no serious side effects were reported.

    •Patients with acute myeloid leukemia, refractory metastatic colorectal cancer, or metastatic melanoma treated with vitamin C combined with other drugs had serious side effects and the disease got worse.”

  16. skeptvet says:

    I certainly agree that anecdotes are a useful way to generate hypotheses to test, though they can never demonstrate a hypothesis true or false. And it is technically true that the absence of evidence is not evidence of absence. That said, the failure to generate convincing evidence after a reasonable effort must be taken as suggestive that there is no evidence to find, otherwise we must indefinitely accept as possible to a meaningful extent every idea forever. One day, someone may jump off a building and not fall, and we may have to rethink the concept of gravity. But it seems unlikely enough that further expenditure on research seems inappropriate.

    Vitamin C has been pretty extensively researched as a cancer therapy, and has failed to demonstrate convincing effects pretty consistently. (e.g. 1, 2, 3). Given our resources for developing treatments are not infinite, it seems appropriate to direct them into more promising areas.

  17. Atn says:

    There are many research papers studying the effectiveness of IV ascorbic acid on cancer. You seem to be pretty biased in your research for information. Here are a couple for you. Feel free to read them.

    Orthomolecular Oncology Review: Ascorbic Acid and Cancer 25 Years Later
    by Gonzalez et al

    Intravenous Ascorbate as a Tumor Cytotoxic Chemotherapeutic Agent
    by Riordan et al

    Intravenous Viatmin C as a Chemotherapy Agent: A Report on Clinical Cases
    by Riordan et al

  18. skeptvet says:

    It’s funny that you accuse me of being biased in my citations (which include a review article 5 years more recent than the one you cite and the American Cancer Society), and then you cherry pick a few papers by dedicated Vitamin C advocates as your evidence. The article makes clear that the evidence is mixed, but the balance is pretty strongly tilted to small, clinically insignificant effects in humans, and there is still no clinical research to support using this in pets.

  19. Atn says:

    The point of my post was to provide you with serious work that was done with IV ascorbic acid. So yes, my post had a biased goal and it did contain cherry-picked material.

    You clearly haven’t read any. From the first paper I reference (by the way these are all fully available online):

    “In the late 1970s and early 1980s, a debate ensued between Dr Linus Pauling (Linus Pauling Institute) and Dr Charles Moertel (Mayo Clinic) due to conflicting results on studies on vitamin C and cancer.150-153 To make the story short, the Pauling and Cameron studies used historical controls and were positive, while the Mayo Clinic studies were done in a prospective randomized double-blinded fashion and had negative results. The Mayo Clinic studies were done with the accepted experimental design used to clarify initial observations but did not truly replicate the Cameron
    and Pauling studies (used a lesser dosage, less time). This issue has been reviewed elsewhere.154
    A critical point of both studies (Mayo Clinic and Pauling’s) is that they used oral doses of ascorbate of about 10 g. Given the saturable gastrointestinal absorption and the nonlinear renal clearance,155 oral absorption of AA cannot achieve plasma concentrations comparable to those obtained by intravenous administration.44 Plasma concentrations of AA rise as the dose ingested increases until a plateau is reached with doses of about 150 to 200 mg daily.
    Moreover, there is a recent report on AA as a toxic agent against cancer cells when given intravenously.94 The doses we are advocating for therapy are substantially
    higher doses (25-200 g) and, most important, are given intravenously. We believe intravenous administration is more effective because plasma levels of ascorbate can reach higher levels than those attained by oral intakes, and these higher levels can be sustained for longer periods of time. These 2 aspects seem necessary to produce a selective toxic effect by AA on cancer cells.We are attempting to reach plasma levels that are 100 times higher than those that can be achieved by oral administration.”

    The clinical trials showing negative results typically use oral doses known not to work as a cancer therapy.

    Please, as a healthcare professional and (hopefully) intelligent individual, be open-minded. There is a lot of work done on IVC by researchers. If done right, IVC can work as a selective cytotoxic substance to cancer cells.

    I haven’t looked into IVC use with animals so I can’t give my opinion about that. My guess is that you haven’t looked much yourself.

  20. Rafael Guzmán says:

    Do not torture your poor pets, when they get cancer, euthanize them. I do not justify chemotherapy or amputations not even for humans, it is torturous. A pet can not complain and all they know is that its guardian who is supposed to protects them is causing pain to them, and with what end? that YOU have your pet for another year or so…

  21. skeptvet says:

    Sorry, but you are simply wrong. I treat pets with cancer all the time, and most of them are happy, comfortable, and enjoy the time we are able to give them. Euthanasia is absolutely appropriate at the right stage, but the idea that we should not even try to teat cancer because it is cruel simply isn’t consistent with what actually happens when we do treat it.

  22. Rafael Guzmán. says:

    I am sorry too, but you are wrong, it is not about if cancer is treatable or not, the point is that the animals suffer the process, even the simply fact to take them to the vet is very unpleasant. The point is they do not choice to be treated, it is YOU who want to treat them against their nature. A human has a choice, they decide to be treat or not, but not your pet ¿what kind of life is for a dog to live without a leg for example or even worst for a cat who enjoys playing around so much. I understand that this is a very polemic theme, but consider this, when a human is treated and suffer of nauseas, pain, hospital time, etc., at least he/she knows there is a reason for that and can (as a matter of fact a lot do) not to continue or be treat at all, but the animal don’t. Beyond the disease they have to deal with, is the “what the hell are they doing to me? And why?” (“if I have been a good dog”), you can see that expression on their faces when they look at you with very sad eyes. So, as I said, I do not even considered good for humans (and I have friends and family who died of cancer), even less for pets. I have a cat right now with cancer, she has the kind of cancer (due to location and other technical issues) is untreatable, I can NOT euthanize her yet, I really can’t, I am administering some shots for pain and “wellness” (vet recommendation of course), but I would not treat her with chemotherapy or anything like that anyway, the reason: she is a rescued cat and is very, very paranoid, when a I met her, she was shaking of terror, even now that she has a safe home, she terrifies when someone get home, to take her to the vet is a very horrible experience for her, thinking in taking her every month or so to treatment is worst than the sickness it self. It is hard to explain, but I truly believe that all she want is “leave me alone”.

    Now beyond that, what should be done is to prevent, I know is a very difficult thing, but the truth is that they are sick for the same reason humans are: food, bad food, nitrates, sugar and all the junk food that is eaten. These kind of disease did not even exist a few decades ago, they are the result of very industrialized food., etc. that is the real problem and there is where the real solution is. After treatment is only a torture and a business for vets, pharmaceuticals and food industries, they commerce with pain and make the pet owners believe that their pets will have a good life, but that is a lie, your pets suffer, They are not toys, They also have the right to die in peace, for a disease caused to them by greed.


  23. skeptvet says:

    It is you projecting your feelings and beliefs onto animals with cancer here. You think it is “against their nature,” so you don’t think they want it. And you project your fears about the side effects of cancer therapies onto these animal without really knowing what cancer treatment is actually like for most of them. I actually treat animals with cancer and your vision of them as frightened and sick and unhappy is not accurate. When I treat a dog with lymphoma who goes from feeling lousy to happy and energetic and well and feels that way for 1-3 years, I know it’s far better for that animal than simply having let them die of their disease or exposing them to untested treatments that often don’t work or even actively harm them without any benefits.

    Sure, some individuals are too fearful of being handled to tolerate chemotherapy, so it may not be right for those individuals, but this isn’t a general rule you can simply project onto every animal with cancer. I know what successful science-based cancer treatment for pets looks like, and it is not the grim suffering you picture. Again, that is you projecting your fears and beliefs outward.

  24. v.t. says:

    Rafael Guzmán,

    You are really misinformed.

    Pets tolerate most chemotherapy better than humans. Depending on the type of cancer, you would be surprised at how many have done well with treatment, not to mention survival.

    Likewise, pets fair extremely well with amputations. Pets don’t know much about limitations and if you’d ever met a pet with a loss of limb, you wouldn’t know it either.

    To deny your pets a fighting chance is…..well, just plain denial and selfishness on your part. Perhaps you need to look more closely into the eyes and hearts of pets who have lived because of chemotherapy, lived happily with three legs, are the same pets they were prior to their illness. They are [i]grateful[/i] for a chance at life, just as you would be. If your kitty could tell you, she would probably want the same chance.

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