Because really I just forget sometimes. Often it can be bad as one dose a week. I do the sublingual B12, as supposedly that absorbs better.
I don't eat salt much so if you're like me, you may need an iodine supplement to maintain thyroid function among a few other small things.
I don’t take any b12, I just consume copious amounts of nutritional yeast and soy milk that have it
B12 is not actually important to consume daily - your body stores over 5 years of B12 naturally, the B12 RDA is just for replacement. If you're taking B12 supplements chances are pretty good the dose you're taking is much higher than your RDA anyways, so I wouldn't worry about it unless you're experiencing symptoms of B12 deficiency these.
I do a daily multi with B12 and iron but also 100%+ of mostly everything else. It's cheap and a lot of days I eat like shit. I think forgetting every so often is fine. Most people's diets regardless of if they consume meat or not is deficient in some regard.
I don't take a supplement most days, which means my only source of B12 is fortified soy milk. I've been that way for years now, and just had a blood test which showed normal B12 levels. Don't know how normal that is though.
I take a multi twice a day, once with my first meal and the other with my last meal. B12 is important to have at adequate levels, but if you eat fortified foods alongside occasional supplementation, you might be alright. Ultimately, a doctor will give you the best information on this matter.
B12, D, and a probiotic. Every day if I remember, but more realistically every few days. Definitely echo others in saying to actually get your levels checked though. I do it every other year or so just to be safe.
I only really take it once a week, though, I do also use nutritional yeast a lot. My last bloodwork showed by B12 as fine, but ymmv.
I take B12 typically once a day but am not that bothered about missing a day or two. I also take a Calcium/Vitamin D2/magnesiumn pill once a day (even before I was vegan) because I have a family history of osteoporosis.
Get one of those weekly pill containers. You'll probably start taking some other daily med eventually so might as well get a head start.