Effect of therapy with vitamin B12 and folic acid on elderly patients with low concentrations of serum vitamin B12 or erythrocyte folate but normal blood counts.

To help understand the haematological significance of the low concentrations of serum vitamin B12 and erythrocyte folate occurring in elderly patients, 17 acute admissions to a geriatric unit with a low concentration of serum vitamin B12 or erythrocyte folate but a normal blood count were treated with vitamin B12 and folic acid for 3 months. Bone marrow deoxyuridine suppression was abnormal in 3 of these 17 patients, 2 of whom also had megaloblastic change in the marrow. With treatment, the MCV fell in 13 of the 17, and the average MCV fell from 90.5 to 87.9 fl (p = 0.007), but the mean Hb did not change. Ten untreated similar patients showed no change in their MCV over the same period, but the mean Hb fell from 14.0 to 13.1 g/dl (p = 0.04). Thus the low concentrations of serum vitamin B12 or erythrocyte folate found in approximately a quarter of acutely admitted elderly patients may indicate true tissue deficiency of these vitamins, even when the blood count is normal.