How much b-12 should I be taking?

Are you taking it orally or as an injection?

Usual Adult Dose for Pernicious Anemia

Parenteral:
Initial dose: 100 mcg intramuscularly once a day for 7 days. If there is clinical improvement and a reticulocyte response, 100 mcg intramuscularly once every other day for 7 days, then once every 3 to 4 days for another 2 to 3 weeks is recommended. Most patients require monthly injections of 100 to 1000 mcg intramuscularly for life.

Nasal Spray or Gel:
Alternatively, cyanocobalamin (Nascobal) nasal spray or nasal gel 500 mcg intranasally to one nostril once a week may be administered to patients with pernicious anemia who require maintenance of normal hematologic status following intramuscular vitamin B12 and who have no nervous system involvement. However, if the patient is not adequately maintained with cyanocobalamin nasal, intramuscular vitamin B12 administration must be resumed.
Usual Adult Dose for B12 Nutritional Deficiency

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Oral: 25 to 250 mcg once a day.
Nasal Spray or Gel:
(Nascobal) 500 mcg intranasally in one nostril once a week
(CaloMist) 25 mcg in each nostril once a day (total dose 50 mcg). May be increased to 50 mcg in each nostril once a day.
Usual Adult Dose for Schilling Test

1 mcg radiolabeled cyanocobalamin orally once after urinary voiding. A 24-hour urinary collection is immediately begun. At 2 hours an injection of cyanocobalamin 1,000 mcg intramuscularly is given to "flush" the patient of absorbed radiolabeled drug. The percentage of radiolabeled B12 excreted in the urine is a measure of how much labeled drug was absorbed. Normally 7% or more of a dose is excreted in 24 hours (< 7% may be considered a positive Schilling test).
Usual Pediatric Dose for Pernicious Anemia

30 to 50 mcg/day for 2 or more weeks (to a total dose of 1000 to 5000 mcg), then follow with 100 mcg/month.
Usual Pediatric Dose for B12 Nutritional Deficiency

100 mcg/day for 10 to 15 days (total dose of 1 to 1.5 mg), then once or twice weekly for several months. May taper to 60 mcg every month.

http://www.drugs.com/dosage/cyanocobalamin.html