It can be done via the GP but I had a nightmare with mine to be honest due to GP and Hospital Phlebotomy Service lack of knowledge. Went in wrong tube 1st so waited a month for invalid result. Then too much bother for GP to contact Hospital Phlebotomy so redo so has to organise it my self and then waited another 3 weeks for a result. Blood test was outsourced to Viapath at St Thomas's Hospital anyway so if you have the finances it may be easier to have it done privately. Then there may be the issue of whether your GP actually understands the results and can provide treatment accordingly! I can only go on my own experience. Sorry I couldn't be more positive. I will send you the link for private blood test.
Sorry for the supper slow reply. My result was 239 (0-280 nmol/L) so no action taken by GP. Have begun sublingual B12 spray as I know I am deficient in a range of vitamins so I am not absorbing them from by stomach/intestinal tract.
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