@AndyPandy haved you had a blood test where MCV (mean cell volume) is measured? It is usually part of the standard blood tests doctors will run. Often, though not always, MCV will be high when B12 is deficient. Doctors don't often bother about it unless it's way out of range. Looking back over my tests by numerous doctors mine has been out of range for many years and not one has mentioned it. Within 6 months of supplementing my MCV is back in the normal range.