Vitamin B-12: Ways to Tell if You Need More/ Testing for Deficiency/ What is Normal?

B12aSince B-12 deficiency (not having enough B-12) can cause a host of medical problems from neurological (seizures, failure to thrive, developmental delays, depression, anxiety, headache, tremors), blood disorders (anemia, blood clots) and poor immune system issues, we need to think of B-12 anytime you or your child is not well.

Traditionally doctors were trained to look for large red blood cells (macrocytic) anemia on a CBC (complete blood count), but high folate can make cells look normal even when B-12 deficient. Many of the symptoms of B-12 deficiency may also be present before the changes are seen in the red blood cells.  

Measuring serum Vitamin B-12 in your blood is likely the best way to see where your levels stand for B-12. Common “normal” levels given by labs range from 180-1,100 pg/ml.

Let’s break that down a little though…
Anything less than 200 would be considered deficient.

Levels found to be in the range of 200-450 are considered borderline. Many hospitals and labs may list borderline as 200-270 and anything above that as normal.

Levels that are greater than 450 are simply considered normal.

Since some studies show that serum B-12 levels need to be above 550 pg/ml for brain and nervous system health, and no toxicity exists for this water soluble vitamin, I would propose that you keep your B-12 levels close to 1000 pg/ml or above.

A second way to test your levels, and one that I use in my office, is to order an assay done by Spectracell that determines the amount of B-12 (along with numerous other nutrients) inside the white blood cells.  This gives you a clue to the amount of B-12 that is getting inside of the cells, where function is so important.  Remember that B-12 is needed for every cell in the body, where, along with folate, it is needed for the conversion of Homocysteine to Methionine and then on to release methyl groups that are so important for the reading of our genetic code (DNA) and for the production of all proteins and neurotransmitters in the body. 


A third test that can help confirm that there is likely a B-12 issue, especially important if your levels are in the borderline zone, is the measurement of urine MMA (Methylmalonic Acid) which is elevated when B-12 is low.  Normal urine MMA levels are  less than 3.8 MMA/mg creatinine.


Another test that can suggest low B-12 is measuring serum Homocysteine. This will be elevated when there is inadequate B-12, low folate, or low vitamin B-6.

Normal Homocysteine (plasma) is 2.0-4.0 micromoles/L.

Due to the costs of all these tests, and the complete safety of B-12, coupled with the devastating consequences of being low in B-12, my preference is to treat anyone who is low in B-12 either on the serum test or the Spectracell intracellular assay, and anyone with the symptoms suggestive of low B-12 if they cannot afford to test.

Consult with your physician if you need testing and for help with interpreting the results.  For treatment with B-12, the best options are typically Methyl B-12 shots, for those with severe symptoms, under the direction of a physician knowledgeable in this form of treatment (Methyl B-12 needs to be compounded) or high dose oral preparations. Most deficient individuals will need oral doses of around 1000 micrograms daily.  Typical oral multivitamins may have 6 micrograms of B-12. Consult your physician before treating in case there are other considerations.  I recommend anyone taking B-12 also take folate in the methyl-folate form.

Dr. Paul



    • Headaches are a symptom with many potential causes, some of which can be serious. I recommend anyone with head pain be evaluated by a physician so a complete history and physical exam can determine if further tests are needed. B-12 deficiency is not typically considered a cause for head pain.

  • Hi, Dr. Paul — I’ve read several of your clear and precise articles this morning and have enjoyed them very much. Thank you! I was wondering specifically about what you consider normal homocysteine levels to be. Your recommendation seems to be much lower than other “normals” I’ve seen. Could you advise or point me to an article or study that backs this info up? Recently, I’ve found out I am homozygous C677T (MTHFR). My homocysteine was 8, which was in the normal range according to the lab and dr. Thanks so much for any help!

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