Abnormal vitamin B12 levels can have various causes, ranging in severity from 'serious' to 'generally fatal'. Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.
Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms. In order to diagnose abnormal vitamin B12 levels, we could:
|CML Leukemia||4%||Ruled out|
|Stomach Cancer||3%||Ruled out|
|Colon Cancer||3%||Ruled out|
|Diabetes II||3%||Ruled out|
|Vitamin B12 Need||1%||Ruled out|
Vitamin B12 (cobalamin). Unit: pg/mL [pmol/L]
Possible responses:→ Don't know
→ Confirmed deficiency in the past
→ Under 200  (low)
→ 200-950 [150-700] (normal)
→ Over 950  (elevated)
A urine MMA test is recommended for properly diagnosing B12 deficiency due to the possible lack of sensitivity of serum B12 tests. A normal or high B12 level makes B12 deficiency less likely, but does not rule it out.