Your body does not absorb sublingual vitamin B-12 supplements, which are dissolved under your tongue, better than other forms of B-12. Considering that your body absorbs very little vitamin B-12 from supplements in general, you might be looking for another way to increase your intake. One way to do so is by taking excessive amounts of sublingual vitamin B-12. Although 2,500 micrograms is more than 1,000 times your daily vitamin B-12 intake, there are no side effects from taking too much vitamin B-12.
Vitamin B-12 Intake and Absorption
Most people obtain the recommended 2.4 micrograms of vitamin B-12 each day from dietary sources, such as seafood, meat and dairy products. However, vitamin B-12 supplements -- or fortified foods -- are extremely important for vegans, as no vegan foods naturally contain vitamin B-12. As your body absorbs only 1 percent of the vitamin B-12 in a supplement, vegans potentially need at least 240 micrograms of supplemental vitamin B-12 to meet their daily intake. As excessive vitamin B-12 presents no health risks, taking 2,500 micrograms of sublingual vitamin B-12 can help ensure you always get enough vitamin B-12 from supplements.
Excess Vitamin B-12
Although you might be worried about overdosing on 2,500 micrograms of sublingual vitamin B-12, the Institute of Medicine suggests that you can't possibly take too much vitamin B-12. This is because B vitamins are water-soluble, so your body can easily deal with extreme amounts of vitamin B-12 by excreting any excess in your urine.