After 16 years of veganism, without taking a single vitamin, my B12 level was checked on October 24, 2012. It was 543 pg/mL. The normal range is between 271-870.
The human body only needs three micrograms of B12 per day, and the bacteria in our mouth and intestines produce it naturally (see links below). B12 is also produced in the earth's soil, which is why some animals have trace amounts of B12 as they eat dirt when they eat off the ground, and animal-feed is never washed. However, attempting to get trace amounts of B12 by eating animal products is inefficient and deadly because B12 is destroyed by heat, and animal products contain disease-causing compounds like cholesterol, saturated fat, trans-fatty acids, casein and animal protein. The heat destruction oexplains why 99 percent of people with B12 deficiencies are meat, dairy and egg-eaters. The other 1 percent are junk-food vegetarians/vegans. The latter groups are also at risk for many ailments because health cannot achieved with cheese, eggs, Ruffles, Oreos, french fries and white rice/bread/pasta. Non-junk-food veganism causes no disease. It is preventative medicine, the treatment and the cure. And there's a reason why the term 'B Complex' was created. It's because any plant product containing a B vitamin actaully has ALL the B vitamins, including 12.
The best way to get B12 is to eat unwashed organic fruits and vegetables with some soil intact. The best sources are barley, beans, chlorella, dulse, grains (all), grapes (concord), kelp, mustard greens, nori, nuts, plums, prunes, sauerkraut (unpasteurized), seeds (all), soy, spirulina, sprouts (all), wheatgerm and wheatgrass. You can also add Red Star nutritional yeast to your meals.