I hijacked a post yesterday to speak about my son who has B12 issues; i got his results back and his B12 level has gone from 156 to 190 in the space of one month during this time I gave him 14 sublingual B12 1000mcg. I expected his level to be really high but it's not the case, which leaves me wondering if he has an underlying problem (he has been tested for PA, no atrophic gastritis, no antibodies) his D3 is also low at 16 despite it being summer, his iron is steadily rising but he's still on supplements. The GP I saw was happy to prescribe 15 loading doses of B12 (it's the injectable form but she wants him to take it orally). I'm not convinced that this treatment will make much difference, but it's better than nothing. I suppose I could continue to give him sublingual B12 but it's frustrating not to have an answer as to why he is like this.