In the US, Neurologists generally will want a referral from your primary care.
this is because the initial visit will be billed as a consultation.
Most insurance plans will not allow you to go directly to a neurologist and give the neurologist full reimbursement, so the offices will want the referral.
A neurologist is often not the correct doctor.
For example, if this is a pinched nerve, as is most indicated by your description, and orthopedist or physical medicine doctor might be more appropriate.
That is for you and your doctor to sort out. In the US typically, the referral to a specialist is a primary care doctor function. We don't replace your primary care here.
A unilateral numbness in the ulnar distribution would rarely be anything to do with electrolytes, metabolic disease or thyroid disease.
Carpal tunnel is more associated with thyroid disease, and this is not carpal tunnel [wrong distribution]. In addition, it is extremely rare for thyroid disease to cause carpal tunnel.
The other potential causes are more systemic, and would not typically be unilateral.
Find me, Dr. Thomas, anytime.
A double board certified US doctor for correct, up to date, clinically accurate answers.