Prescription opioids are used in clinics for reducing pain, but overdoses and addiction can lead to poisoning. Herein, we report a rapid, straightforward, and cost-effective hydrophobic deep eutectic solvent-based liquid phase microextraction process with HPLC-UV detection for extracting and analyzing morphine and codeine from whole blood samples. The procedure involved synthesizing seven deep eutectic solvents and investigating their pH switchability. Deep eutectic solvents with pH-switchable properties were employed as extractants. Under optimal conditions, the relative standard deviation of 50 μg/L of morphine and codeine in blood samples was 5.4–6.2 % for inter-day measurements and 3.7–4.3 % for intra-day measurements. For both analytes, the calibration graphs showed a linear range of 1.5–300 μg/L and a limit of detection of 0.5 μg/L. The enrichment factor and the extraction recovery of morphine and codeine were 152–––166 and 76 − 83 %, respectively. The results revealed that the addicted person’s blood sample contained both morphine and codeine. The real blood samples spiked with varying doses of codeine and morphine had relative recoveries ranging from 91.8 to 107.0 %, suggesting the method is suitable for real sample analysis.