123 mcg to mg

123 mcg = 0.123 mg

To convert micrograms to milligrams, divide the microgram value by 1,000. So 123 mcg ÷ 1,000 = 0.123 milligrams.

Because the two differ by a factor of 1,000: 123 micrograms is only 0.123 milligrams. Vitamin D, folic acid and levothyroxine are dosed in micrograms for exactly that reason — reading mcg as mg would mean a thousandfold overdose.