The British National Formulary (BNF), the British Society of Haematology Guidelines, NHS Clinical Knowledge guides, Integrated Care Board guidance notes such as this one from NHS Cambridgeshire and Peterborough, Vitamin B12 full guidance
Improved Sleep Some people find that better B12 levels help regulate sleep patterns and promote restful sleep
Yes, my first probable COVID infection led to a 2 1/2 month headache , that pressure type one that kept turning into migraine

Other causes of hand numbness include: Carpal tunnel syndrome (causes pressure on the nerves in the wrist and often occurs with overuse of the hands and wrists) A herniated disc that puts stress on the spinal nerves Nerve pressure caused by tumors, infections, or enlarged blood vessels Shingles Herpes infection Certain medications Vitamin B12 deficiency Abnormal levels of calcium, potassium, or sodium Excessive alcohol use Vasculitis (inflammation of the blood vessels) Lyme disease (a vector-borne disease that causes a small red bump at the site of an insect bite) Stiffening of the arteries, causing a lack of blood flow to the area Poor circulation due to diabetes Stroke Migraine headaches Underactive thyroid Raynauds syndrome (a condition that leads to artery spasms, reducing blood flow to the hands) Ganglion cyst (a noncancerous tumor that grows along the joints or tendons in the wrist
Sterility Check Ensures the medication is free from bacteria, fungi, and other contaminants
Review preventive and supportive-care services available through Nao Medical