Those who can't get to sleep at night may need vitamin B12. Studies
show that B12 causes an earlier release of melatonin at night which
resets the sleep-wake cycle. (Melatonin has been called "the sleep
hormone" because of its effects on sleep). B12 acts directly on the
pineal gland to provoke a faster release of melatonin. At the tail
end, B12 ...
As you said, B12 is highly soluble in water and unused quantity is easily excreted from the body as urine. Therefore, it is nearly impossible to get an overdose of B12, even if you exceed the recommended daily intake.
However, the component which possibly have a very small risk is cyanocobalamin because it releases a tiny amount of cyanide within the body ...
There is a PDF here Meeting Calcium Recommendations on a Vegan Diet
There are many plant-based sources of calcium including certain leafy
green vegetables, broccoli, some types of tofu, almonds, black beans,
vegetarian baked beans, and blackstrap molasses. Vegans can also
choose from among calcium-fortified foods including fruit juices,
Some sources express concern about taking too much B12 in supplements. Others disagree and claim that it's perfectly safe. Google "b12 overdose" and read some articles for yourself, there's too much to effectively quote here. While it's much better to risk the potential rare side effects of taking B12 than to risk having a deficiency, if you don't have a ...