Are there any conditions that could lead to me being deficient in b12 even when i supplement with sublingual tablets?

Refractory B12 Def: Inconsistent or sporadic intake & under dosing are the more likely culprits. Oral intake or a different formulation may be tried. If B12 levels are very low at time of diagnosis & not treated with injection, it may explain the persistent low b12. Other blood & urine tests can help confirm is a true B12 deficiency is present.A few rare congenital/cellular conditions which may cause B12 deficiency.