From the Research
A vitamin B12 level of 700 pg/mL in a man with fatigue is normal and not likely the cause of his symptoms. Normal B12 levels typically range from 200-900 pg/mL, so a value of 700 falls well within the healthy range 1. The fatigue is probably due to other causes that should be investigated, such as sleep disorders, depression, anemia from other causes, thyroid dysfunction, or other medical conditions.
Potential Causes of Fatigue
- Sleep disorders
- Depression
- Anemia from other causes
- Thyroid dysfunction
- Other medical conditions Additional testing would be recommended, including a complete blood count, thyroid function tests, metabolic panel, and iron studies 2. A thorough medical history and physical examination are also important to identify potential causes of fatigue. While B12 deficiency can cause fatigue, weakness, and neurological symptoms, this patient's B12 level is adequate and supplementation would not be expected to improve his symptoms unless there are other indicators of functional B12 deficiency despite normal levels 3.