B12 side effects

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My B12 was low so my gp started me on injections. I had the loading dose, no problems but after my first maintenance shot I started experiencing numbness and

tingling in my hands and feet. I didn't have them before. My levels are now quite high and I just wondered if anyone else has had a reaction like this. I had no neurological problems before.


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  • Posted

    It is not uncommon for some symptoms to seem to get worse before they get better as the B12 starts to repair the damage done to the nervous system caused by the deficiency - so ironically the fact that you "feel worse" after the injection is a probably a "good sign".

    You say " I had no neurological problems before" - what symptoms did you have?

    What frequency of injections are you on?

    Testing your serum B12 level after an injection is pretty pointless as it is bound to be high in the bloodstream.

    Do you know what your iron and Folate levels are as these two work together to make red blood cells and a deficirency in one or other may stop them all working properly?

    I am not a medically trained person but I've had Pernicious Anaemia (a form of B12 deficiency) for 45 years.

    I wish you well.

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    • Posted

      Hi Clive,

      Thanks for the reply. I don't have PA. Just posted on here because no other b12 forum. My levels when tested were critically low. I had no symptoms. The nerves weren't damaged. I've read that several stories of people who have reacted to b12 with various horrible side effects, Even though it says it's no toxic people do get these side effects and so just wondered if anyone had on here, If so, will they go?

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    • Posted

      Generally speaking a B12 deficiency affects and damages the myelin sheath at the end of the nerve prevening the signal to be transmitted to the brain.  As this damage is repaired messages start getting sent to the brain from parts of the body it had "lost contact" with.

      When you say you had no symptoms perhaps you were not as accutely aware of them as others who suffer Weakness and fatigue.

      Light-headedness and dizziness

      Palpitations and rapid heartbeat

      Shortness of breath

      A sore tongue that has a red, beefy appearance

      Nausea or poor appetite

      Weight loss


      Yellowish tinge to the skin and eyes and a whole host of others.

      Many athletes supplement with B12 to improve energy & performance levels and (of course) report no neurological side effects because they aren't deficient in the first place.

      I hope you get to feel better soon.

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    • Posted

      Thanks Clive again for taking the time to reply. I don't agree at all though. I don't have PA and am accumulating too much b12. Not the same as you at all. Too much can produce the side effects I am experiencing and be harmful to the body in some people. I've read lots of accounts of the same. I was healthy and fine until I took b12. I won't be having anymore.

      I guess I posted on the wrong place.

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    • Posted

      You said in your opening post that you now have "tingling in my hands and feet" and blamed them on the B12 injections.

      In my previous reply I listed the symptoms of B12 deficiency which might have applied to you when you said you said yours was "critically low" (your first reply).

      Below is what happens If low levels of B12 remain for a long time, the condition also can lead to irreversible damage to nerve cells, which can cause the following symptoms:

      Numbness and tingling in the hands and feet

      Difficulty walking

      Muscle weakness


      Memory loss



      PsychosisYou may not have been aware that you had symptoms before your treatment started but you're certainly showing signs of the top one on the list above which would suggest that you will need to continue with the injections and as Marion says "If you do stop B12 treatment you may be risking long term nerve damage".

      Marion also raises a good point in that it would be a good idea if you can identify why you became deficient in the first place.

      The following are all potential causes of a B12 deficiency:

      Alcohol consumption


      Vegan or vegetarian lifestyle

      Excessive junk food consumption

      Digestive diseases and conditions which block absorption (Celiac, Crohn’s, IBS, malabsorption, etc.)

      Removal or resectioning of the small bowel

      Use of antacids and prescription drugs used to treat ulcers

      Gastric bypass surgery

      Are you on any precription drugs such as Metformin, Proton Pump Inhibitors, anatacids, certain contraceptive pills, and some antibiotics and cholesterol medications.

      Parasitic infection

      Liver dysfunction

      Ageing – everyone absorbs less B12 as they age. Some experts recommend that anyone over age 50 should take a B12 supplementWe cannot "overdose" on B12 as being water soluble any excess is excreted via our urine.

      You didn't post in the wrong place as P.A, is just another form of B12 deficiency and the treatment is pretty much the same - the main difference being that with P.A. B12 can only be obtained via injection whereas it can only be

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    • Posted

      My previous comment was "interrupted" by a moderator but just to finish what I was saying Vitamin B12 can only be sourced naturally by eating animal products - red meats, fish, seafoods, eggs, poultry, and dairy produce.  

      If you don't have any digestive problems or any other of the list of possible causes of your deficiency is your diet lacking in the above foods?.

      I was given two years to live back in 1972 and was told that I must either eat raw liver, three times a day or have B12 injections for the rest of my life. - I chose the injections and I'm still "clivealive" at 75.

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  • Posted

    Did the doctor find any reason why your B12 had become low? Were you vegetarian or vegan? Do you have digestive issues, Crohns or Celiac disease? If you do stop B12 treatment you may be risking long term nerve damage.
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