Testing B12 during treatment

During treatment with vitamin B12 injections, serum B12 is often tested to ascertain the frequency of injections, to see if the value rises, or to base maintenance treatment on.
However, this value says nothing about the effect of the treatment. The patient’s symptoms should be the only guideline for basing treatment. After a loading dose of 10 injections in 5 to 10 weeks, a maintenance dose can be determined based on the symptoms.

When obvious neurological symptoms are present, it is recommended to give frequent injections (weekly or even twice weekly) for a longer period of time. Other patients can reduce the frequency slowly based on the symptoms. When symptoms reoccur, the time between two injections is considered too long.
Because there is no danger of overdosing vitamin B12, it is preferred to base treatment upon the individual needs of each patient in order to attain optimal recovery.

Some patients can have a bi-monthly maintenance dose straight after the loading dose. However, a large number of patients experience recurring symptoms on bi-monthly injections. It is not clear why, but large groups of people need much more vitamin B12 than the recommended maintenance dose to feel well and prevent recurring symptoms. Research in to that question is underway.
One of the most common problems in the treatment of a vitamin B12 deficiency is that people receive insufficient injections to feel well. Often the serum B12 value is used to ascertain the frequency but there is no correlation between the serum B12 value and the symptoms experienced by patients. Also many physicians are, erroneously, afraid of an overdose.

Scientific information that serum B12 cannot be used as a guideline for treatment:

  • Henk Russcher, Sandra G. Heil, Lennert Slobbe en Jan Lindemans, Approaches to vitamin B12 deficiency Ned Tijdschr Geneeskd. 2012;156(1):A3595. “During vitamin B12 injections, transcobalamin en haptocorrin are fully saturated with vitamin B12. Therefore, serum and Active B12 values cannot be used to ascertain the effect of treatment.” See: Vitamine B12-deficiëntie, p. 8, under ‘Valkuilen’.
  • R. Carmel, How I treat cobalamin (vitamin B12) deficiency, 2008: “Cobalamin and holo-transcobalamin II levels are uninformative because they rise with cobalamin influx regardless of therapeutic effectiveness”. See: How I treat cobalamin (vitamin B12) deficiency, p. 6.
  • L.R. Solomon, “Disorders of cobalamin (Vitamin B12) metabolism: Emerging concepts in pathophysiology, diagnosis and treatment”, 2006, under: “FALSE” HIGH/NORMAL VALUES staat: “Recent Cbl therapy”. See: Disorders of cobalamin (Vitamin B12) metabolism, p. 5, tabel 1.

From the Standard B12 Diagnosis Dutch GP Society:

Control of the vitamin B12 status during treatment is considered to be of little use.

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