flagyl metronidazole thiamine deficiency

Metronidazole Toxicity, Thiamine Deficiency, and Wernicke’s Encephalopathy

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Dr. Marrs and I recently had a book published with the title of “Thiamine Deficiency Disease, Dysautonomia and High Calorie Malnutrition”. I was therefore extremely interested to read one of the book reviews published on Amazon books by a patient who had suffered from what has become recognized as metronidazole toxicity encephalopathy (brain disease). Subsequently, she shared her full story with us. It is published here.

A Comparison of Flagyl Induced Encephalopathy and Wernicke’s Encephalopathy

This drug, sold as Flagyl, is prescribed to treat infections caused by anaerobic bacteria and protozoa. Uncommonly, it causes central nervous system toxicity that has the same damage configuration in the brain as Wernicke encephalopathy (WE). WE is the condition that occurs in the brain in people with severe thiamine deficiency. A manuscript in the medical literature was entitled “Metronidazole-Induced and Wernicke Encephalopathy: Two Different Entities Sharing the Same Metabolic Pathway?”  There seems to be little or no effort to explain it as a cause and effect relationship rather than seeing the two situations existing with different causes.

Debilitating Symptoms Post Flagyl

The reviewer states that she has, for two years, suffered with what she describes as debilitating symptoms due to a reaction from Flagyl. She states how these symptoms mysteriously wax and wane. On some days she barely notices them, but of extreme importance, she adds that a mild illness or physical exertion will cause the symptoms to reappear, forcing her back to bed for a variable number of days. When she was taking the drug, she lost his ability to walk and speak, but experienced a dozen other symptoms that persisted. These include difficulty in swallowing and breathing, constipation, severe anxiety, insomnia, depression, heart palpitations, chest pressure and several other unspecified problems. She mentions that she has a borderline enlarged heart.

I must point out here that these additional symptoms are surprisingly common in patients attending physicians in America, often classified as psychosomatic. It is the anxiety, insomnia and depression that guides physicians to thinking that the entire list of “inexplicable” symptoms is psychosomatic. Even the use of the word borderline for heart enlargement indicates that the physician could not identify the total symptomology. If thiamine deficiency had been considered as a diagnosis, the “borderline enlargement” would have fit because it is a cardinal sign of this deficiency.

The patient had evidently done some research on her own and had discovered that metronidazole is a thiamine antagonist. She also reported that in the medical literature metronidazole toxicity is constantly being compared with WE. When she came across our book, she had evidently experienced a flare up of symptoms and began to take supplements of thiamine and magnesium. She stated that the flare up calmed down much more rapidly than usual, enabling her to return to work and function in social activities.

She discovered that doctors do not believe in adverse drug reactions and will not treat the condition since they will not acknowledge that it exists. As a result, she has started a support group for people who suffer from this toxicity. Starting with three affected individuals, there are now over 100, all of whom have the same symptoms. Interestingly, they even warn new members how their doctors will react, preparing them for the reality of being dismissed by the medical community.

Thiamine Deficiency and Psychosomatic Disease

As mentioned in our book repeatedly, the multiple symptoms described by this reviewer are common in the offices of American physicians. “Real” diseases, according to the present medical model, are supported “by laboratory confirmation”. Because vitamin deficiency is generally considered to be nonexistent in America, it is only a physician, open to the possibility, who will entertain the laboratory studies required. The cause of many abnormal current laboratory studies performed on behalf of a sick patient is often obscure. None are capable of identifying vitamin deficiency. When positive as a result of the biochemical changes induced in the body by the deficiency, they are ascribed to other conditions that are acceptable to the present medical model. Hence, the diagnosis of psychosomatic disease often rescues the physician from a failure to recognize his own ignorance. It has always seemed to me that blaming the patient for imaginary symptoms without thinking of the brain as an electrochemical machine represents a glaring deficiency in diagnostic perspective. Unfortunately, nutrition has for long been a neglected area of medical teaching and there are extraordinarily few physicians in practice who recognize its vital importance. What is even more important is the recognition that many drugs are capable of precipitating something as bizarre as thiamine deficiency.

Stress and Illness

I mentioned above that it was extraordinarily important for the reviewer to recognize that flare ups of symptoms occur following a mild illness or physical activity. To explain this, I turn to the teachings of Hans Selye, one of the early researchers in the effect of stress as a causative agent in precipitating disease. Stress must be defined as any environmental factor that imposes a necessity for an animal to adapt (resist). Just like a car that climbs a hill, energy requirement must increase to meet the demand. Mental stress is often more energy requiring than physical stress, explaining the breakdown of health that may follow divorce proceedings. Selye had recognized in animal studies that virtually any form of physical or mental stress imposed the requirement of some form of energy in the ability of the animal to adapt. This was pure genius because energy metabolism was largely unknown in Selye’s time. Modern biochemistry has unraveled a lot of its complexities and thiamine stands out as an absolute necessity in the production of energy. Adapting means that the animal being physically stressed in many different ways would be capable of maintaining a state of health. Failure to meet the increased energy demand was marked by many observed performance and biochemical changes commensurate with those seen in sick humans. One of Selye’s students had reproduced in thiamine deficient animals exactly the same manifestations as those caused by physical stressors.

Diseases of Adaptation or Maladaptation?

The conclusion must be obvious. Any form of mental or physical stress induces a complex reaction in the organism that requires a large amount of energy to run the necessary adaptive machinery. In fact, Selye had concluded that illnesses in human beings were what he described as “the diseases of adaptation”. Since it is a failure to furnish the necessary energy, I suggest a refinement by calling them “the diseases of maladaptation”.

A healthy diet is designed to meet the calorie and non calorie nutrients that fully enable the body to synthesize energy. If this capability fails to meet the demand, even under extreme environmental conditions that permit life to continue, disease follows. The weakness may be genetic or nutritional in character or the stress overwhelming. For everyday life, all three factors are in play continuously.

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Derrick Lonsdale M.D., is a Fellow of the American College of Nutrition (FACN), Fellow of the American College for Advancement in Medicine (FACAM). Though now retired, Dr. Lonsdale was a practitioner in pediatrics at the Cleveland Clinic for 20 years and was Head of the Section of Biochemical Genetics at the Clinic. In 1982, Lonsdale joined the Preventive Medicine Group to specialize in nutrient-based therapy. Dr. Lonsdale has written over 100 published papers and the conclusions support the idea that healing comes from the body itself rather than from external medical interventions.


  1. Help please…I already suffer fatigue, candida, Hashimotos and atrial fibrillation. I am 54 female don’t smoke or drink, I walk a lot and eat well. I had a tooth extracted and got a dry socket which was agony. My dentist gave me Flagyl which I did not want to take. Dentist scared me about the infection and possibility of Sepsis. I have not taken antibiotics for 30 years. Two weeks following a six day course I can’t think straight, my legs are like lead weights, arms heavy, chronic fatigue and brain fog, dizzy. Please what can I do I take a b complex oil I buy from Australia and have always taken b1 and b2 liquid drops from metabolics but only tiny amounts as I can’t tolerate, how can I take more if I get bad reactions? I also spray magnesium but again not much due to reactions. I have high oxolates low b12.

    • Flagyl is a thiamine antagonist. Lower the amount of oxalates you are eating. Lower the amount of carbohydrates you are eating and keep reading Dr Lonsdale’s and Dr Chandler’s articles on how to increase your thiamine intake.

  2. Dr Lonsdale,

    this is very interesting. I experienced a health crash immediately following an injection of gadolinium based contrast which was preceded by two rounds of antibiotics (although not flagyl or FQ’s). Many of the article’s symptoms are identical to my experience. Symptoms were 30 long. The only thing that ever clued me in on thiamine was developing a problem with oxalates following my original poisoning, which led to histamine and salicylate Intolerance as well.
    I’ve been taking low doses (50mg) of TTFD, still struggling with lots of digestive symptoms, food intolerances and a limited diet which clearly is not helpful. Browsing and reading on here I found Elliot Overtons Article on Thiamine’s relationship to IBS, SIBO C, pancreatic enzyme deficiency etc. All of which I’m experiencing even though I have implemented a low oxalate diet a year ago already in hopes it would cure many of my problems . I intend to start upping my thiamine to see if it will help in any of my issues at all. But this leads me to two questions
    Do you think in certain individuals Gadolinium could worsen or create a Thiamine deficiency and

    Could thiamine deficiency be a root cause of Leaky gut?

    • I think that you might have been mildly thiamine deficient before the injection and the stress precipitated a more severe deficiency. It is classic stress as described by Hans Selye. Thiamine deficiency causes energy deficiency, particularly in brain and virtually any symptom can result. That is why the vitamin B1 deficiency disease called beriberi has a huge number of symptoms, non of which are pathognomonic (clearly indicate beriberi).The recklessness of modern medicine is a disgrace.

  3. I’ve come across this page and another by Erin after weeks of searching for help. I took repeated doses of metronidazole and have experienced all of the symptoms. My gp is now refusing to see me and has diagnosed a somatic syndrome. I have been so low as I know this isn’t the cause. I’ve been off metronidazole for 3 weeks but still have all the symptoms. I have just ordered some me thiamine and magnesium and will start a course and hope…. I’ll update here should I have any updates, I hope this works as right now I feel like my life is over.

  4. Dear Mr. dr. londsale

    I would like to thank you for your commitment in the field of thiamine science.
    After 2 years diffuse problems after cipro and metro I feel completely normal again after 5 weeks of thiamine intake.
    I never thought that this unimpressive vitamin has such a great influence.

    many Greetings

    a medical doctor from Germany

  5. Dear Dr Londsale,
    I need your recommendation: how long should i take thiamine? my doctor recommends 3-6 months.

    I take 400mg of thiamine for brainfog and dizziness/ataxia after Cipro and metronidazole

    Thank you!!!

  6. Hello

    I took metronidazole and ciprofloxacin in May 2017.
    My symptoms were:
    Ataxia and dizziness as well as Brainfog,
    Panic attacks, anxiety, tiredness and fatigue, many more CNS symptoms, vitreous detachment, plantar fasciitis, achillodynia …

    Except for ataxia, braininfog and dizziness, all symptoms are gone. Now that I’ve read about thiamine, I take 300mg of thiamine HCL daily.
    After a week, the Brainfog is almost gone, no ataxia and no dizziness (which lasted 2 years).

    Can it really have been a BeriBeri after such a long time?

    • Very interesting but not surprising to me. ALL the symptoms are typical of mild to moderate lack of brain oxidation (i.e. beriberi). Panic attacks are caused by spontaneous activation of the sympathetically driven fight-or-flight reflex. I had a case record of a patient with plantar fasciitis in whom I was able to prove thiamine deficiency. Achillodynia and ciprofloxacin are associated. Ataxia, brainfog, and dizziness are typical of defective brain mitochondria energy compromise from thiamine deficiency. You might do better with Lipothiamine from Ecological Formulas and I suggest that you add a hefty dose of magnesium .

      • dear doctor

        I live in Germany and here the lipothiamin is not available. even from the eu I can not buy it.
        there is only thiamine HCl or benfotiamine.

        which dosage would you recommend me with thiamin hcl? I now take 200mg in the morning and 200mg in the evening. to a total of 600 elemental magnesium.

        Thank you!

          • from 200 mg of thiamine, my ataxia and dizziness disappeared. brainfog only a little there. That’s why I take 400 mg of thiamine
            I took cipro and metronidazole in may 2017.

  7. I had flagel in July I got neuropathy from it it’s been 5 months still have it will the thiamine and magnesium help it heal about how long does it take a lot of
    Anxiety and fear the doctor put me on zanix

    • Thiamin deficiency causes anxiety as well as the neuropathy. Thiamin and magnesium supplementation alleviate both. Be patient, it takes time

  8. Would you think that Floriquinolone toxicity would have a similar metabolic reaction? I found some tests done on rats in vivo shows the tendon lesions induced by Ciprofloxacin were perfectly identical to those induced by magnesium deficiency. I would assume thiamine would play a role as magnesium is involved in the same processes.

    I took Cipro for a kidney infection and the first dose gave me a rash and intermittent tendon pain, not consistent. I’ve been taking thiamine and magnesium religiously and it seems when I first dose in the morning the intermittent pains completely go away. It’s only been 5 days after I discontinued the drug. I had a similar reaction with Levaquin and was completely symptom free in a couple weeks. I have suspicion my quick recovery is probably because of my age (21) and thiamine and magnesium supplementation.

    What do you think if the floriquinolone toxicity issue becoming quite prominent these days?

    • I believe that various forms of toxicity precipitate thiamine deficiency, making it extremely important as an essential maintainer of mental and physical health.

  9. Thank you for the article, Dr. Lonsdale. I’m really happy to know that my experience with metronidazole toxicity might help other people with this condition better understand what’s happened to them, and how to treat it.

  10. https://www.facebook.com/MarchAgainstMonstanto/photos/a.566016720083519.1073741828.566004240084767/1840244725994039/?type=3&theater
    Can it be possible? I guess it can! On the top of that we are eating lots of foods contaminated with glyphosate. The reality is organic food is expensive and the majority of us cannot pay for it. Regarding the antibiotics, I always hear that we are taking too much, but in fact, the cows and chickens that are taking too much!! That is changing our gut flora! I believe that the fungus may even have influence in what we crave altering our taste and “need” for more sugar.

    • The word “need” is misleading to many readers although this comment uses it to indicate “desire”. The point that I am trying to make is that there is absolutely no physiological need for sugar as a commodity as distinct from that contained in fruit. It has been shown by animal study that it is more addictive than cocaine. The reason for this is because it sends a powerful pleasure signal from the tongue to the brain. The medical profession has never accepted this addiction because it would mean that addiction from the consumption of sugar would have to be treated as a disease. Even cancer has been associated with the consumption of fructose syrup.

  11. Thanks Dr Lonsdale….it seems to me the key to defining thiamine deficiency is getting a lab in the USA to preform this Erythrocyte Transkelotase test. How can we get some lab to do this Thiamine test and why doesn’t any lab do it already? I read where the Cleveland Clinic was starting a functional medicine department and hiring a bunch of functional doctors….perhaps it will arise from that….in time.

    I wanted to say something about sugar consumption. I’ve felt your frustration and disbelief in your posts on America’s sugar consumption. I really feel it’s an addiction brought on by gut then brain imbalance. Through the overuse of antibiotics and other gut altering meds, combined with the eating of carbohydrates. We are killing the good gut bacteria..the fighters…the balancers and feeding the bad gut yeast….the fungus…the acetaldehyde producing candida. What does yeast love?-Sugar…feed me sugar! The now plentiful bad guys in the gut are telling the brain what they need to survive. In my opinion thats the clinical cause of the American sugar addiction. I can avoid sugar all day, but come night time the sugar cravings control my brain….”Feed Me” says the “Little Shop Of Horrors” I have growing in my gut….in my brain?…in my tissues? Now I know they say systematic candidasis is a secondary condition, that a healthy immune system kills it, I get that. But don’t they also say 70% of your immune system is in your gut….if your gut is overrun by these “evil weeds” thanks to the American cipro and carb ingestion combo, it’s a good bet 70% of your immune system is not healthy. Which is the root cause for many chronic diseases. I think there may be a thiamine deficiency connection with this. I’ve read that the highest edible source of B1 is that Australian favorite Vegemite…which is a yeast extract. It’s a good non pathogenic yeast versus a bad, toxin producing, tissue eating yeast such as candida. It’s a survival of the fittest yeast in your gut perhaps? It would be interesting to know what the rates of thiamine deficiency in Australia are. I know they hate jam on their toast in the morning and a salty palate pervades over an the American sugary one.

    There is a doctor at Case Western Univ. by the name of Mahmoud Ganholm, he has studied fungus for 40 years are you familiar with his work?

    Your thoughts and thanks again for being a true healer


        • I am well aware of the opinion represented by the Mayo Clinic and the Cleveland Clinic. The blood level of thiamin can be perfectly normal when there is clinical thiamin deficiency. The reason for this is that there must be a ratio of carbohydrate calories to the concentration of available thiamin. Millions of people are taking empty carbohydrate calories. A simple analogy would be that of choking an internal combustion engine. Too much gasoline (glucose) overwhelms the ability to ignite it (thiamin). They have also reported that they do the red cell transketolase test without the thiamin pyrophosphate uptake. For the same reason this can be normal in the presence of clinical thiamin deficiency. This is why orthodoxy has claimed that this kind of deficiency is exceedingly rare in America. They are missing the boat constantly.

          • I like the theory doc, it makes a whole bunch of sense. But we have to find a way to test it correctly here in America, where the problem now resides. It seems to me the Japanese have good knowledge of beriberi, any idea how they handle testing it ? Is this an “Only In America” issue? In regards to the whole blood test (TDP) since that’s what is available here. Could one eat a bunch of carbs right before the blood draw and see a substantial drop in total thiamine levels? I say this because of my experience now of eating carbohydrates and how quickly I can fall asleep after. Then waking up with increased beriberi/fibro/candida(?) like symptons.

  12. Thanks for looking at all factors for our collective chronic disease, Derrick. I work with youth and adults, many living on the streets, many out of prison, many fighting co-occurring mental diseases, many in recovery or various stages of relapse.

    The stress in their lives is more than just debilitating in spirit and agency. The stress viably draws life out of my clients. Stress when they were youth growing up still splits their biology as adults. Epigenetics of just witnessing stress — mental duress — has determined many of my clients maladaptive behavior, drug abuse, and criminal proclivities.

    Yet, we are in the Dark Ages in terms of how we as a society or societies deal with people under stress not seen, stress such as structural violence, poverty, debt, and what we consume in our mental worlds.

    What we do to fellow humans is absolutely bizarre, since we are supposedly the highest form of animal in the kingdom.

    Why Zebras Don’t Get Ulcers is a powerful book by Sapolsky on how the human condition is in 24/7 mental, intellectual and spiritual stress. Diet and physical health are fine, but the mental strain of our society and the economic and penury punishments meted out by our Capitalist system are much more dramatically negative on a person’s whole being than a cornucopia of drugs, booze and bad food on the human biome.

    Good stuff here:

    The Uniqueness of Humans | Dr. Robert Sapolsky Class Day Lecture 2009


    Here, our odd human behavior:

    How can humans be so compassionate and altruistic — and also so brutal and violent? To understand why we do what we do, neuroscientist Robert Sapolsky looks at extreme context, examining actions on timescales from seconds to millions of years before they occurred. In this fascinating talk, he shares his cutting edge research into the biology that drives our worst and best behaviors.


    We need to really rethink this project of Capitalism:

    The World Medical Association (WMA) in 1949 and again in 2006 stated: “A physician shall not allow his/her judgment to be influenced by personal profit or unfair discrimination,” and “shall not receive any financial benefits or other incentives solely for referring patients or prescribing specific products.”

    Doctor Nayvin Gordon is a Family Physician in California who has written many articles on Health and Politics:

    The exsanguination of medical ethics has helped bring us to this dangerous moment in history. We have witnessed a craven transformation of medical ethics when physicians, nurses and other health providers are clamoring to sign up for “Value-Based Bundled Care”. The AMA has betrayed their ancient oath as healers, in service to an economic system that puts profits before people. While deadly epidemics of cancer, heart disease, obesity, diabetes, violence and addiction haunt the nation, we have been led into a partnership with Dracula.

    • I have a suggestion for you Paul.Your work is very important and I respect you for it. I have been convinced for many years that poor nutrition, as exemplified by the people for whom you care, is responsible for violent crime. But stress is passed off as being “purely psychological” without considering that this represents a biochemical mechanism. Sugar and even fat, (think doughnuts) induces relative thiamin deficiency (if you have a mechanical mind, think choking a car engine). The cheapest treatment would be to supply these individuals with megadose thiamin and magnesium in the form of supplements, since you will never be able to change their diet. Most people in the world today are educated towards taking pills for everything. The expenditure for obtaining them might be your cheapest method!

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