Milligrams (mg) and micrograms (ug) are metric units, 1mg = 1000ug. 1 milli = 1000 micro, followed by the same conversions for both length and weight units. Milligrams and micrograms are both units of weight, 1 gram = 1,000 milligrams = 1,000,000 micrograms, 1 kilogram = 1,000 grams, and are widely used in medicine when doctors prescribe medications. For example, folic acid, some special drugs, including anti-cancer drugs, etc., are measured in micrograms. Patients taking certain drugs, the specific dose will involve milligrams, micrograms of conversion, need to be careful and cautious use, specific should follow the guidance of a professional doctor to avoid adverse consequences.