does vitamin b12 injection make you sleepy Side Effects and Safety Feeling worse after B12 Injection:

Nicotinamide N-methyltransferase inhibition mitigates obesity-related metabolic dysfunctions in diet-induced obese mice

Check out my videos The Optimal Vitamin B12 Dosage for Adults and The Optimal Vitamin B12 Dosage for Kids, Pregnancy, and Seniors which go into detail

You can start at a higher dose (say 2,000mcg) then reduce to half once you feel better

Have a look at your previous tests, I think NHS only look at TSH and free T4 which doesn't always give an accurate picture of the thyroid

Healthcare providers, to achieve correct and timely reimbursements against their treatments, must find the underlying cause and then document the precise code

doi:10.1007/s00253-017-8616-7