Can you have any reactions or side effects from vitamin B12 injections? Most documentation papers indicate you might experience any of these:
- Mild diarrhea and/or upset stomach.
- Difficulty breathing or swallowing.
- Weight loss or weight gain.
- Nervousness or restlessness.
- Nausea or vomiting.
- Headaches or migraines.
- Paresthesias (tingling sensations).
- Rhinitis (chronic sneezing or a congested, drippy nose).
- Skin reactions, such as rash, itching, swelling, blisters, or pain at the site of injection.
- Light joint pain.
- Lightheadedness or dizziness.
- Chest pain or discomfort.
- Low blood potassium levels.
- Irregular heart beat.
- Feeling unwell and sick.
- Chills, night sweats, fever, or hot flushes.
However, people fail to recognize one thing. When patients have suffered a B12 deficiency through a disease like pernicious anemia, then quite often the disease is only diagnosed at the end stage. Many of the reported side effects of vitamin B12 injections are consistent with the disease itself. But adverse effects are recorded in a way that necessitates their inclusion as B12 injection symptoms as well.
So, No Side Effects to B12 Injections?
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.
B12 is a water-soluble vitamin. That means any excess is quickly flushed out through the urine. You can’t overdose, and there’s no toxicity threshold. It is harmless and often used in ultra-high doses. For example, B12 shots of 25-50mg each (nearly a whole monthly vial of ours) have been used to treat cyanide poisoning, neuropathy, and ALS.
That being said, the conversion of severe anemia to normal production of red blood cells could temporarily lead to low potassium levels and high platelet count. Therefore, monitor these two, and you may want to increase your potassium intake in the first few months of injecting. Read our pernicious anemia diet page for more advice.
Allergic Reactions to B12 Injections
Anaphylactic reactions (strong allergic reactions) have been reported, though very rarely, to either cyanocobalamin, hydroxocobalamin, or both:
- Here’s a case of a 52 year old woman who reacted to an intramuscular (IM) cyano B12 shot. She later received oral B12 with no adverse effects.
- Five years after starting treatment, a 89 year old lady developed signs of malaise, collapse and vomiting one hour after a Neo-Cytamen shot (hydroxy B12).
- Here’s another case of an anaphylactic shock after having hydroxy B12.
- A 55 year old woman suffered an allergic reaction after her second dose of an intramuscular cyano B12 shot.
- Here’s a case of a 54 year old pernicious anemia patient who had an anaphylactic shock twenty minutes after his sixth hydroxy B12 shot.
- A 42 year old woman developed an immediate bad reaction to intramuscular cyano B12, even though her intradermal testing was positive.
- Here’s a rare case of a woman who had immediate adverse reactions to both cyano B12 and hydroxy B12, by both injection and oral delivery.
- Cases of allergic reactions to hydroxy B12 with tolerance to cyano B12 were recorded here, here, and here.
Is The B12 Causing The Reactions?
Allergy to vitamin B12 is uncommon. However, once diagnosed it presents a difficult management problem in patients suffering from pernicious anemia, as there is no substitute.Allergy to vitamin B12
Don’t fear the cases above. We scoured the medical database looking for allergic reactions to B12 shots, and this is all we could find. Remember, millions of people around the world have had B12 shots. Considering the number of injected patients and the amount of reported cases, you get the idea how rare reactions really are.
Why do I feel worse after my B12 injection?
If you reacted to B12 shots in the past (if it had anything to do with the shots at all), the cause was likely not the B12, but some troublesome excipient in the mix. Mannitol and carboxymethyl cellulose are common additives that may cause acute reactions.
If you’re sure the B12 was pure, then the next question would be, was the correct fluid added to the vial? If anything other than sterile saline was added, it may have been a preservative that you had reacted to. For example, here’s a case of a 67 year old man who reacted to a hydroxy B12 shot that contained 1.5% benzyl alcohol. Here’s a verified case of adverse reactions to vitamin B12 shots due to benzyl alcohol sensitivity.
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
Here’s a case of two female pernicious anemia patients who had negative reactions to hydroxy B12 shots. The author of the study, Dr. Rosa Caballero, said that “the allergens involved in vitamin B12 reactions is likely to be a hapten.”
Does Our B12 Have Any Side Effects?
Many readers of this website self-inject regularly. However, we have never had anyone come back to us with an allergic reaction to our B12. Not a single case. We have many repeat customers, so it must tell you something about how rare a true allergy is.
Our injectable B12 is methylcobalamin, which is an active, native form with no recorded anaphylactic reactions in medical literature. Zero cases. It comes 100% pure, no additives or preservatives whatsoever. Also, methyl B12 is the most absorbable form, with distinct nerve repairing properties. For most people it is the best form.
Patients with Leber hereditary optic neuropathy should not take methyl B12 shots. Hydroxy B12 shots, though less effective, are safer, because this disease can get worse in those high in methylcobalamin levels.
If you order your B12 shots anywhere else, make sure it comes from a certified lab that follows stringent pharmacy regulations. Also, make sure it doesn’t contain benzyl alcohol, or at least check that you’re not sensitive to it. If you’re injecting a premature newborn, avoid benzyl alcohol at all cost due to the risk of gasping syndrome.
And please, stay away from cyanocobalamin. It is a synthetic form of B12 that contains cyanide attached to the B12. Many B12 deficient folks (especially those with pernicious anemia) have trouble clearing out the cyanide. For them, it can make things worse.
What If I Still Worry?
If you suspect you might have a cobalt allergy (again, extremely rare), have your doctor supervise and give you an intradermal test dose first. Look for reactions such as skin rash, swelling, a blue tint to your skin, chest tightness, etc. Maybe have your doctor do it with our pure methyl B12, which again, nobody has ever reported any negative reaction to.
Vitamin B12 injections side effects are remarkably rare. What’s more, reactions are more likely to be the result of additives rather than the B12 itself. To make sure your B12 is free of any additives, you may want to try a vial of our pure methyl B12.
Good luck, and stay safe.