T,
If you take any B vitamins I think you should consider taking a BALANCED B COMPLEX supplement of all the various B vitamins together. They have a relationship where they work together, and often if you are defiicent in one due to diet you are quite likely to be deficient in others that they may not test you for. So even if your doctor gives you say a B12 shot, it won't hurt to get a bottle of B-Complex 25mg or 50mg pills and take those as well to ensure you are getting ALL the B vitamins. P.S. take them with food as they can be strong on an empty stomach.
Just my personal opinion...