I'm 46 with brain fog and my mum has vascular dementia and Altzheimer's
You are right about many GPs not knowing a lot about nutrition. Vitamin B-12 has been well researched - there are books about it and how the lack of B-12 can cause many ills, including dementia symptoms. B-6 is often given with B-12. Ideally, you would find a doctor who understands alternative medicine, including nutrition and supplements.
Sublingual drops are often better absorbed than pills. As we age, our bodies often absorb less B-12 (and other nutrients). My personal thoughts, for me, are that these are good for us. However, there may be reasons you shouldn't take them, so do try to find a different doctor. At the very least, don't use huge doses without guidance. But you are right to investigate this.
The following info. is from the internet. It seems there is a product with sublingual methyl b12 that combines folic acid and b6.
Thanks for your kind response Nina. I know I should start with the G.P. but he
really doesn't seem to know much and is unwilling to do the necessary tests
I am sorry that your Mom has vascular dementia and Alzheimer's. My father-in-law has late stage of Alzheimer's. But the chance for getting it as the adult child may be as small as 4% or none. I don't mind taking health products such as B12 or Q10 for preventative care. I am not sure about B6. But you should talk to your family doctor to make sure there is no problem with it. Sometimes try to take it moderately. A large dose of vitamins at times may bring you side effects in the future.