A Study to See if a Combination of Vitamins That is Injected Into a Muscle is as Good and Safe as a Vitamin That is Taken by Mouth

Primary efficacy objective: To investigate the effects of a parenterally vitamin B12 combination treatment versus an oral vitamin B12 mono therapy on the vitamin B12 status in female and male patients as determined by the change from baseline in serum vitamin B12 concentration after 4 weeks (28 days) of treatment. Secondary efficacy objectives: To evaluate the effects of a parenterally vitamin B12 combination versus an oral vitamin B12 mono therapy after 4 weeks of treatment on: * Serum holotranscobalamin * Serum homocysteine * Serum methylmalonic acid * Combined vitamin B12 markers (cB12) * Serum folic acid * Serum vitamin B6 * Serum S-adenosylmethione (SAM) * Serum S-adenosylhomocysteine (SAH) * SAM/SAH ratio * WHO-5 Well-Being Index * Medical Outcomes Study Questionnaire Short Form 36 Health Survey (SF-36) * Visual analogue scale (VAS) EQ-5D. Safety objectives: To evaluate the safety and tolerability of oral vitamin B12 mono therapy versus intramuscular vitamin B12 combination.