Microgram (mcg or µg) and milligram (mg) are metric units of mass commonly used to measure very small quantities, especially in pharmaceuticals, vitamins, supplements, and laboratory measurements.

One milligram equals 1,000 micrograms (1 mg = 1,000 mcg). To put this in perspective, a milligram is one-thousandth of a gram, and a microgram is one-millionth of a gram. These tiny measurements are crucial for medication dosages where precision is essential for safety and efficacy.

The notation "mcg" and "µg" are both acceptable ways to write microgram, though "mcg" is often preferred in medical contexts to avoid confusion with "mg," as handwritten "µ" can sometimes look like "m." Confusing these units can result in a 1,000-fold dosage error, which can be dangerous or fatal.