I feel so sensitive under my feet. it's like electric shocks. i've used vit b12 for 2 weeks, but it remains. i sometimes have my left feet swell.

Neuropathy: B12 deficiency can cause one type of peripheral nerve injury that can give symptoms like you are describing. So can chronic trauma and diabetes. Replacing the B12 will not help in that short of time particularly if you are having a problem absorbing B12 from your diet. See your physician to look at all the causes and perform an exam.

Check for diabetes: Need to be screened for diabetes as neuropathy may be cause.

B12 wouldn't work in: B12 wouldn't work in two weeks. And if you had defiency neuropathy, you might have paradoxic increased parasthesias as nerves mend. I can't say what your problem is, but unilateral foot swelling is possibly another issue, and certainly unrelated to b12. See a doctor. No harm taking b12!