µg is the correct symbol for the metric measurement microgram which is one millionth of a gram or one thousandth of a milligram.
The symbol for µ is a Greek letter (mu) which means 'small'.
Due to the symbol µ being typographically unavailable much of the time i.e. you cannot type it on a keyboard, other versions were devised; two of which are ug and mcg and are now widely used in its place.
A healthy balanced diet is the best way to consume all the nutrients we need. Sometimes however this isn't possible and then supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying any supplements or herbal medicines.