Display omitted •N doped carbon dots were prepared by facile hydrothermal treatment of fish scales.•Highly fluorescence and anitinterference features were achieved in the carbon dots.•The carbon dots probe displays high capability for detection of LH in human serum. Fluorescent carbon dots (CDs) were synthesized through hydrothermal treatment of an easily available fish scales precursor. The as-prepared CDs exhibit good water-solubility, wavelength-tunable fluorescence nature with fluorescence quantum yield of 9%, high photostability and resistance against common ions and biomolecules, thus enables the application as viable fluorescent nanoprobes for detection of pharmaceuticals molecules. The fluorescence of CDs can be efficiently quenched by lidocaine hydrochloride (LH) through static quenching, hence the CDs can serve as a simple and rapid fluorescent probe for determination of LH pharmaceutical. The fluorescent CDs probe demonstrated a wide linear range (0.185–1.295 mmol L−1) and a low detection limit (0.054 mmol L−1). The CDs also demonstrates low cytotoxicity, which enables the accurate fluorescent detection of LH in human serum.