Hi, Have been directed here as a result of a post on Thyroid UK . I posted the results from a Blue Horizon Thyroid +11 blood test. There was a slight confusion over the B12 level. i.e., 659 pmol/L (range 140 - 725). Their suggestion was that 659 was not optimal, suggesting 900 would be more reasonable, especially for a 69 year old with waxing and waning symptoms including fatigue, weakness, foggy head, some loss of balance, among others. Bear in mind I take multi-vitamins and 250 mpg B12 daily. Any contributions gratefully received!