µ
you can't use mg cause that is milligrams. there are 1000 micrograms in a milligram.
1000 µ = 1 mg
On a Mac you can hold down the option key when tying the M.
Just checked the Link Silva provided.
According to Nutrition facts.
For adults under age 65, the easiest way to get B12 is to take at least one 2,000 mcg supplement each week or a daily dose of 50 mcg. Note that these doses are specific to cyanocobalamin, the preferred supplemental form of vitamin B12, as there is insufficient evidence to support the efficacy of the other forms, like methylcobalamin.
As we age, our ability to absorb vitamin B12 may decline. For those over 65 who eat plant-based diets, the supplementation should probably be increased up to 1,000 mcg of cyanocobalamin each day.