1. if you aren’t deficient you most likely have many months of b12 store.

2. the tablet is about 1000x what your body can absorb daily. Don’t take two.

3. unless you are just starting the treatment for a profound deficiency don’t sweat about it, but do build yourself a better system to remember.

4. you won’t be anemic because you forgot a few dose, same thing with neurological symptoms: if you feel bad there is probably another explanation.

This isn’t medical advice because we don’t live under the same laws and maybe i don’t have your full information…

Some vegan look into yeast as a source of b12 : same problem than the tablet you need to remember to add it to your recipes. Since your lack of b12 comes from a diet choice we can expect your stomach to produce the “intrinsic factor” required to absorb b12 : you are fine.