I have looked at sublingual vitB12. The ones I bought are 1000mcg. It’s difficult to work out the dose because each 1000mcg tablet only supplies a very small dose of the vitamin into the blood stream ,I’m not sure exactly how much. The recommended daily dose of B12 is 2.4 mcg. The supplement manufacturers ought to state how much B12 is absorbed from one tablet and then the actual dose could be established