Is it mL or mL

Both "mL" and "ml" are acceptable abbreviations for milliliter, though "mL" with capital L is preferred in formal scientific and medical contexts to avoid confusion with the numeral "1" (one). The International Bureau of Weights and Measures (BIPM) recommends lowercase for unit symbols (ml) following SI conventions, but recognizes that the uppercase L variant (mL) reduces ambiguity in handwriting and certain fonts where lowercase "l" resembles the digit "1".

In practice, you'll encounter both forms across different fields and regions: medical dosing and pharmaceutical documentation predominantly use "mL" for clarity and safety (preventing medication errors from misreading 5 ml as "5 m1"), while scientific publications may use either "ml" or "mL" depending on journal style guides. The key principle is consistency within a document or organization—choose one form and use it throughout. Both forms are universally understood and represent the same volume: one-thousandth of a liter or one cubic centimeter (1 mL = 1 ml = 1 cm³ exactly). For informal contexts, either abbreviation works acceptably, but in medical, pharmaceutical, or contexts where misreading could have serious consequences, "mL" with capital L provides superior clarity and reduces potential for dangerous errors in dosage interpretation or preparation.