Yes B12 deficiency may cause fatigue but THAT problem is being addressed in your case ....
You should consult your doctor again due to your fatigue ..
Fatigue may habpve many potential causes
The QUALITY of fatigue is helpful to divide up possible causes ----
Sleepy during day ? Need more hours of rest to feel ok? Do you have shortness of breath? Feel tired easily with exertion? Do you lack get up and go to get up off the couch ??
Common potential causes of fatigue may include ...
Anemia/ hypothyroidism/ sleep disorders such as sleep apnea/ low sodium ( hyponatremia) / dehydration / depression/ pulmonary disease such as asthma / heart disease such as congestive heart failure ...
So many categories and many causes
Follow up and discuss your symptoms with your doctor
I hope that this information is helpful for you
Let me know if you have further questions or concerns
I will be happy to get back with you
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Thank you and Best Regards,
Anthony Bray MD