Can taking too much B12 kill you?
No.
B12 is water-soluble, and it’s generally safe even at very high doses. In the complementary medicine realm B12 is probably one of the safest things you could take.
Fat-soluble vitamins like A and D are harmful in excess, because they build up in fat stores. In contrast, a person injecting 1,000µg of B12 will only absorb a small fraction of it, and urinate the rest. For this reason, there are no B12 overdose symptoms.
You Can’t Overdose On B12
Consider the following:
- Methyl B12 has been used in ultra-high daily doses (25,000-50,000µg a shot) to prolong survival of ALS patients in Japan. Their ALS progressed slower, and those patients survived much longer than untreated patients. Another study from Japan found similar results (from similar ultra-high doses), with no adverse effects.
- Intravenous ultra-high dose (25,000µg a shot) of methyl B12 has been shown safe and potentially effective therapy for patients with peripheral neuropathy and chronic axonal degeneration.
- When treating children with an inherited disorder of B12 metabolism and transport, serum levels are kept at around 7,500pmol/L with no side effects.
- In the fifties, when chemo wasn’t yet widely used, high-dose B12 shots (10,000µg) were given to children with a neuroblastoma tumor, every two days, for 2-3 years. In most patients, the tumor disappeared either entirely or partially.
- In life-threatening cases of cyanide toxicity, 5,000,000µg of B12 is injected. Blood levels quickly rise to 560,000,000pmol/L, and if necessary, treatment is repeated within hours for a total of 10,000,000µg of B12. This is more than 4 million times the recommended daily intake, yet still there are no B12 toxicity symptoms outside of a few harmless and temporary effects, such as red skin and faster heart rate.
- In Japan, treating multiple sclerosis patients with a daily tablet of 60,000µg methyl B12, for six months, was proven useful and safe.
- Also in Japan, kidney dialysis patients with polyneuropathy received 5,000µg methyl B12 shots, three times a week for six months. Because of their malfunctioning kidneys and renal clearance, the B12 remained in the blood, and serum values rose from an average of 422 pmol/L to 54 000 pmol/L, without side effects.
- The American Institute of Medicine, Food and Nutrition Board, and the European Scientific Committee on Food, have all decided it would be unnecessary to set an upper B12 intake limit, because toxicity from overdosing on B12 poses no risk. No adverse effects have ever been recorded from taking excessive amounts of B12.
So Why Are Doctors Afraid?
Doctors are trying to keep B12 blood levels within range, because of an unrealistic fear of toxicity or overdose. But as you saw, the scientific literature shows that treatment with extremely high doses of B12 – leading to extremely high blood levels – is 100% safe. To this day, not even a single harmful case of B12 overdose has ever been recorded.
Because of this unfounded fear of overdosing on B12, doctors often drastically reduce treatment, or stop it altogether. This is tragic, because pernicious anemia symptoms resurface quickly, and can become permanent. Patients are left with recurring, crippling symptoms, which could be avoided if treatment continued. Doctors must understand, B12 blood levels will rise during treatment, regardless of therapeutic effectiveness.
It’s very possible that doctors’ concern for a possible B12 toxicity may be the result of the fact that high levels of B12 often accompany an underlying, sometimes deadly condition. It could be cancer destroying healthy cells and releasing B12 back to the blood, a bad liver that can no longer store B12, or an increased production of the transport protein haptocorrin, to which blood B12 binds. High levels of B12 are a warning sign:
While low serum cobalamin levels do not necessarily imply deficiency, an abnormally high serum cobalamin level forms a warning sign requiring exclusion of a number of serious underlying pathologies.
The pathophysiology of elevated vitamin B12 in clinical practice
Elevated levels of serum cobalamin may be a sign of a serious, even life-threatening, disease. Hematologic disorders like chronic myelogeneous leukemia, promyelocytic leukemia, polycythemia vera and also the hypereosinophilic syndrome can result in elevated levels of cobalamin. Not surprisingly, a rise of the cobalamin concentration in serum is one of the diagnostic criteria for the latter two diseases. The increase in circulating cobalamin levels is predominantly caused by enhanced production of haptocorrin. Several liver diseases like acute hepatitis, cirrhosis, hepatocellular carcinoma and metastatic liver disease can also be accompanied by an increase in circulating cobalamin. This phenomenon is predominantly caused by cobalamin release during hepatic cytolysis and/or decreased cobalamin clearance by the affected liver. Altogether it can be concluded that an observed elevation of cobalamin in blood merits the a full diagnostic work up to assess the presence of disease.
Significance of elevated cobalamin (vitamin B12) levels in blood
Those high levels aren’t a sign of B12 toxicity or overdose. They are side effects.
Why Are People Reporting Symptoms of Too Much B12?
We’ve come across online discussions where people complained about symptoms they attributed to B12 toxicity, overdose or reactions to B12 shots. They mentioned weakness on one side, nightmares, dizziness, anxiety, insomnia, restlessness, numbness, nausea, muscle spasms, tingling, itching, acne, psoriasis, eczema, leg cramps, heart palpitations, hair loss, blurred vision, and not being able to concentrate or to stand noise.
Do those symptoms remind you of anything?
That’s right – they are the symptoms of B12 deficiency. People fail to recognize that many of the reported symptoms come from B12 deficient people (many due to pernicious anemia) who are supplementing. Often, their disease is only diagnosed at the end stage, and many of the reported reactions to B12 are consistent with the disease itself.
For another example, a person might have undiagnosed pernicious anemia. Seeing his low blood levels, his doctor might prescribe an oral B12 supplement. Since tablets won’t work in PA, the anemia will only get worse, and the patient may end up blaming the symptoms on the B12 itself, rather than on the accelerating, untreated anemia.
Another problem is allergies and sensitivities.
Many of the side effects described by others bear a strong resemblance to symptoms of allergic reactions, which ultimately can be attributed to any number of variables present at the time of B12 ingestion. For example, let’s say the B12 in question came in the form of a tablet which also contained any number of ingredients for fillers, binders, coloring, etc, and which some may be sensitive to. If the B12 ingested was part of a multivitamin, then the list of potential sources for a reaction becomes quite formidable.
We hope this gives some insight into the problematic nature of pinpointing cause and effect within the constraints of such a complex environment.
That being said, we do have some recommendations to follow.
Our Advice
Avoid Cyanocobalamin
Cyano B12 is a synthetic, slightly-toxic, inactive form of B12 that is made with a cyanide donor. However, it doesn’t absorb well, and requires a methyl donor (a natural antidote and an antagonist for toxins) to detoxify it before it can convert to one of the useful forms of B12. It’s the most prescribed form, because it’s cheap, but it’s also the least safe or effective, and is the most demanding type of B12. It makes no sense to try to improve your health with something that depletes you of other crucial substances.
Can B12 kill you? No, but cyanocobalamin toxicity may be real:
A young woman was treated with multiple daily doses of 1 mg of cyanocobalamin for severe pernicious anemia. After a total dose of 12 mg, she developed acne, palpitations, anxiety, akathisia, facial ruddiness, headache, and insomnia. She improved two weeks after stopping the drug. There were no sequelae nor complications.
Toxicity induced by multiple high doses of vitamin B 12 during pernicious anemia treatment: a case report
Or it may not. As we discussed, these symptoms are exactly the symptoms of B12 deficiency or pernicious anemia, of which the young woman already had.
Either way, stay away from cyanocobalamin. Many people with B12 deficiency or pernicious anemia are naturally low in methyl donors, and have trouble detoxifying the cyanide. The donor responsible for the decyanation seems to be glutathione, which PA patients need for lowering their homocysteine. Cyano B12 is also risky to smokers, or to those with methylation, liver or renal issues, which make it hard to clear cyanide.
Make Sure Your Supplement Is Pure
At the very least, make sure you’re not reactive to any of the additives. Can you overdose on B12? No, but you can react negatively to other ingredients in supplements.
Allergic reactions to proprietary preparations of vitamin B12 might be due to substances added to the solutions as preservatives or for other reasons, to impurities from the production, or to the vitamin B12 itself.
ANAPHYLACTIC REACTION AFTER INJECTION OF VITAMIN B12
If you think you had reacted to B12 in the past, the cause was likely not the B12 itself, but some other ingredient in the mix. Mannitol and carboxymethyl cellulose are common B12 shots additives that you may have reacted to. Or it may have been the fluid that was added. If it was anything other than sterile saline, it may have been a preservative that you reacted to, such as benzyl alcohol. Here’s an example case of adverse reactions to B12 shots due to benzyl alcohol sensitivity.
If you’re looking to buy a pure supplement, try our 100% pure injectable methyl B12. Methylcobalamin is an active, native form, with zero recorded anaphylactic reactions in medical literature. It comes 100% pure, no additives or preservatives whatsoever. It also has distinct nerve repairing properties. For most people, it is the best form.
Monitor Your Nutrition
The conversion of anemia to normal production of red blood cells could temporarily lead to low potassium levels and high platelet count, causing an irregular heartbeat or high blood pressure. So when you first begin supplementing with B12, increase potassium intake. Supplement with other minerals and vitamins if you’re low in them, so that you don’t confuse their deficiency symptoms with reactions from the B12 supplement.
B12 needs folate and the other B vitamins in order to function properly. If you decide to take a B12 multivitamin complex, try getting the pure forms without any added junk in capsules or injection solutions. Check out the list of ingredients, and stay clear of any preservatives, potassium sorbate, food coloring, etc. This will minimize your risk for unexpected reactions, that you might then blame on the B12 itself.
Read our pernicious anemia diet page for more advice.
Cobalt Sensitive?
If you’re allergic or sensitive to cobalt, you may react to B12, because it contains cobalt atoms. If you’re worried you may have it, go and test for cobalt sensitivity. Alternatively, just have your first injection next to a medical professional supervising you.
B12 Toxicity: Summary
Can too much vitamin B12 kill you?
As you’ve just learned, no.
The treatment of PA and other ailments with ultra-high doses of B12 is 100% safe, and also very effective. Don’t let the imaginary fear of overdosing delay your treatment, as timing is crucial. If you start early, you can reverse PA symptoms completely, before any irreversible damage takes place. And if you think you took too much B12, don’t worry. Even injecting a whole vial of 15,000µg of B12 at once can’t do you any harm.
Unlike in the case of vitamin D or A, the danger of overdosing isn’t real. Excess vitamin B12 can’t kill or hurt no one. If you have pernicious anemia or B12 deficiency, we recommend treating based on symptoms alone. Disregard blood values.
Good luck, and be healthy.