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HIGH VIT B12 level in blood. Is it bad?

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Hi, Question regarding my 2.5 year old son. He recently had some blood work done a CBC, iron test, and vit B12, thyroid test. Dr said everything looked normal, but when he showed me the results the vit B12 was flagged as "high" at around 1400. I questioned him about it and he said that was good not bad. Upon googling, I have seen that high vit B12 can mean serious things like cancers etc but Dr was not concerned. He does take a multivitamin daily which includes B12 and he did not fast for the test. Just wanted to get a second opinion as I have sent myself into a panic. Does this sound concerning to you?


Category: Pediatrician

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Category: ICU/ Critical Care Specialist
 30 Doctors Online

Thank you for posting your query at
I can understand your concerns. Your apprehensions are justified. High vitamin B12 levels are a marker of some underlying abnormality. That is true, but partially.
In a symptomatic child, where Vitamin B 12 level estimation was clinically justified, it would have some interpretation. But, in an asymptomatic child, it does not carry much importance.
Secondly, getting the test while on multivitamin supplements does not make much sense to me. What time did he ingest his dose of multivitamins? What was the time interval between the multivitamin tablet and blood sampling? These are some of the things that could affect the results.
Thirdly, every person undergoing a serum B12 estimation should have fasted for at least 8-10 hours. Food substances like meat can directly affect the serum B12 levels. Similarly other food items may also play a role. So, without appropriate fasting, the results may not be reliable.
Given all these fallacies, I suggest a two-fold approach.
1. If your child is symptomatic or unhealthy (signs/ symptoms of renal/liver failure/ recent onset anemia/ weight loss/ malaise), stop all multivitamin supplements for at least 2 weeks and repeat a Vitamin B 12 level after appropriate fasting precautions.
2. If your child is Asymptomatic (which is most likely in your son's case), forget about the test result and move on. This is the problem with doing unnecessary investigations. If you do ten such investigations in a completely normal individual, one of them is likely to come back abnormal. That is pure chance.
Hope I was able to clarify your doubts.
Dr. Saptharishi L G

Dr. Saptharishi L G
DM (Pediatric Critical Care) Senior Resident

Patient replied :

Hi, Thanks for your response. The test was done about 6 hours after ingesting a multi vitamin. Also, he does not eat any meat, he is vegetarian by choice. He does however consume lots of dairy ( milk, yoghurt, cheese). He has not been acting ill the tests were done as a routine anemia panel as he does not eat any meat and does not have many iron rich foods in diet. CBC test was normal, iron level was at 11 which dr said wasnt too bad but I could give him a maintnance does of iron to prevent deficency in the future. Also the dose of B12 in his milti vitamin is 1.5 mcg. I was just simply surprised and confused that when i questioned my dr about the high B12 he said "Its not a bad thing its a good thing" since I read contradictions online.

Thank you for the added information. The fact that he has taken it six hours prior to testing definitely makes the test result unreliable.
Generally, in an asymptomatic child, there is a very minuscule chance that your child has a chronic liver/kidney disease/ a hematopoietic malignancy. Probably with that understanding, your doctor could have tried to reassure you.
Hope this was helpful,

Patient replied :

Ok thank you. My final question to you about this is that if his elevated B12 was caused my a leukemia wouldn't his CBC be abnormal? Or does B12 elevate before the CBC becomes abnormal with leukemia? Lastly , is 1400 for b12 considered a slight elevation or severe? I've noticed some labs have a range going up to 1100. Also, is it possible just to have a higher b12 level with no cause of concern ? Thank you

Dear Parent,
Your child does not have leukaemia. None would dare make that diagnosis on an asymptomatic child with high Vit B 12 levels (on multivitamin supplements). Please do not worry.
Medicine is a complex speciality. Two and two do not always make four. So why unnecessarily add more confusion to this discussion. I can go on and describe 'aleukemic leukaemia' and so many variants that we see in clinical practice. It does not serve any purpose. The questions that you have posed are good for a medical seminar on pediatric hemato-oncology.
Normal range varies from lab to lab, based on the technique employed by the lab. Your child has higher Vit B 12 levels because of the fact that proper precautions were not undertaken prior to testing. I think we have discussed everything in detail.
Take care

Dr. Saptharishi L G
Category: ICU/ Critical Care Specialist
Senior Residency: DM,  Pediatric Critical Care, PGIMER

Residency: MD, Pediatrics, Postgraduate Medical Education & Research (PGIMER), Chandigarh, 2013

Internship: JIPMER, 2009

Medical School: MBBS, Jawaharlal Institute of Post-graduate Medical Education & Research (JIPMER), Puducherry, 2008
Dr. Saptharishi L G and 4 other Medical Specialists are ready to help you

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