For most young adults, the best vitamin B12 supplement is either methylcobalamin or cyanocobalamin. Methylcobalamin is the active, naturally occurring form that the body absorbs easily, while cyanocobalamin is a very stable and well-studied option. Both standard oral tablets and sublingual tablets (which dissolve under your tongue) are highly effective at restoring healthy B12 levels. A common daily dose of 1,000 micrograms is generally safe and works beautifully. I suggest checking in with your doctor for a simple blood test to find the perfect dose tailored just for you.