Sublingual absorption of vitamin B12 tends to be slightly higher than absorption via oral administration (swallowing). Absorption rates will vary from person to person due to a number of factors, including enzyme activity, diet, size, age, etc.
We are not able to provide an estimate for the percentage of B12 that each individual will be able to absorb or utilize. However, some studies suggest that those lacking intrinsic factor may only absorb about 1% of B12 supplements. Working with your doctor to have your B12 levels tested before and during B12 supplementation can help you and your healthcare professional determine whether you are efficiently absorbing and utilizing the B12 and make adjustments as needed.*