Intended for healthcare professionals

Practice Rational Testing

Investigating vitamin B12 deficiency

BMJ 2019; 365 doi: https://doi.org/10.1136/bmj.l1865 (Published 10 May 2019) Cite this as: BMJ 2019;365:l1865

Re: Investigating vitamin B12 deficiency

There was a doctor who developed some neurological symptoms (intermittent numbness on the left side of the face, left hand or left knee) a few weeks after an episode of shingles affecting the left side of the body. He saw a specialist who decided to check his Serum B12 and Serum Folate levels.

The B12 level was low (135ng/L) and the Folate levels were normal (7.9 micrograms/L). Intrinsic Factor antibodies were negative. It was recommended that the doctor start receiving intramuscular hydroxocobalamin injections. However, the doctor did not want to receive intramuscular injections for the rest of his life. He was aware that many of his patients had low B12 levels which returned to normal without treatment. It also seemed to him that his symptoms did not correspond to any of the B12 deficiency neurological syndromes (e.g. peripheral neuropathy or sub-acute combined degeneration). In view of this he said that he did not want the hydroxocobalamin injections.

The doctor's GP was very understanding and it was agreed not to treat, but to repeat the tests. However, the doctor did agree to follow his wife's advice to add a small amount of yeast extract on a slice of bread to his diet occasionally.

The tests were repeated a few months after the original test. They showed normal B12 levels (221ng/L) and low Folate levels (2.8micrograms/L). However, the doctor did not want to start treatment with daily folic acid for the rest of his life.

The doctor's GP was very understanding and it was agreed not to treat, but to repeat the tests.

The tests were repeated a little while later. They showed normal B12 (285ng/L) and normal Folate (4.2 micrograms/L) levels.

The doctors neurological symptoms have been investigated by another specialist who has not insisted on treatment for B12 (or Folate) deficiency. The symptoms have been improving despite no treatment for B12 deficiency or Folate deficiency.

I am that doctor.

Are we overtreating patients with low B12 levels?

Does the BMJ article encourage the overtreatment of patients with low B12 levels?

Competing interests: No competing interests

24 June 2019
Peter D Gibson
Consultant Geriatrician
North Manchester General Hospital