vitamin deficiency disorder vitamin B deficiency A condition due to deficiency in any member of the vitamin B complex. These B vitamins are water-soluble and must be obtained from the diet because they are easily lost in the urine. Unlike the lipid-soluble vitamins, they cannot be stored in the body fat. MESH:D014804 MONDO:0042976 NCIT:C35129 SCTID:47903000 UMLS:C0042850 deficiencies, vitamin B deficiency, vitamin B vitamin B deficiencies