Are you B12-deficient?

The first stage is to check your Signs and Symptoms.  Symptoms of B12 deficiency are generally non-specific, that is, they could be caused by a number of different things.  It's only when you have a number of different symptoms, occurring at the same time, that it makes sense to look for a common cause such as B12 deficiency.

And of course your GP (General Practitioner, Family Practitioner, Primary Care Doctor) is where you should start.  You may know your symptoms better than anyone, but your GP knows what to do about them - as long as you are prepared to discuss them openly and honestly.

Your doctor should ask about your symptoms, your family history, and some other information (such as whether you are vegetarian, drink or smoke a lot, take Nitrous Oxide - yes people die because NO stops the B12 working), and will usually then take blood for a blood test for, amongst other things, MCV, U&E, Folic Acid, B12.  MCV (Mean Cell Volume) tells if you have undersized cells (a sign of anaemia/anemia or iron deficiency) or oversized cells (macrocytosis - a sign of problems in the folic acid pathway exacerbated by B12 deficiency and used to diagnose Pernicious Anaemia/PA/Pernicious Anemia), and the rest highlight what other conditions may be causing problem.  For example, protein in the blood tells the doctor a whole lot of things.

Sometimes the GP will rely on the lab to say whether someone has B12 deficiency or not - but labs all use different thresholds and really it is up to the GP, who has you in front of them, to include the B12 level in their assessment of what is the cause of your symptoms.

Ultimately, the best way to tell if B12 deficiency is the problem, is a therapeutic trial of B12 injections (hydroxocobalamin, but preferably not cyanocobalamin).  This should be in the form of a “loading dose”, ie 2 weeks’ of alternate day injections 1mg.  If the symptoms remain then they were caused by something else (this isn’t always the case; for example if you have severe MS then you may need other things eg Vit D, thyroxine, cortisol to kick start your body again for a short period whilst the B12 stabilises everything and restores the hormones to their normal balance and gets you out of doors to get your Vit D performing); if you get relief then B12 is of value. 

It’s useful to have a serum B12 level, but in general we find that it is a poor predictor (apart from the really complicated tests like MMA, Homocysteine, Schillings etc which are all even worse) of whether the symptoms will be relieved by B12 replacement therapy – the proof is in the pudding/ does it work?  You can start B12 injections the moment your blood has been taken – if your doctor will let you.

 B12 isn’t the answer to everything, and your GP will make a differential diagnosis to exclude other conditions which could need urgent treatment.  But many of the “difficult” conditions such as Chronic Fatigue Syndrome, loss of power in a limb, pins and needles, difficulty swallowing, difficulty controlling the eyeball (especially where this is one-sided), neuroses, dementia (well, that’s the main neurological ones + fatigue – there are also symptoms related to hormones eg unexplained hair falling out, digestive problems, gynaecological problems including heavy periods, etc) all seem to get a whole lot better with lots of B12 intake.