Lead (Pb) poisoning is estimated to account for 1% of the global disease burden. The gold standard for diagnosing lead poisoning in human body relies on blood lead level (BLL), which is always performed in hospitals using expensive instruments. However, there are still many countries and regions with a lack of medical resources (without enough professional medical staff and analytical instruments). To achieve a facile diagnosis of lead poisoning by ordinary residents (without any expertise), this study conducted a research study on 810 participants to discover and validate a new lead poisoning indicator (creatinine-corrected urinary lead level, cULL) beyond BLL in non-invasive samples. A point-of-care testing (POCT) device to measure cULL was developed, equipped with liquid-phase microextraction and electromembrane extraction on a paper-based analytical device for on-site separation of lead and creatinine in the urine, using a smartphone for the quantification of analytes. The cULL as a novel indicator and the POCT device developed could be effective in reducing the risk of damage from lead contamination. Environmental implicationLead (Pb) is a priority hazardous pollutant and a group B2 human carcinogen owing to its high toxicity toward organ systems. Lead poisoning is estimated to account for approximately 1% of the global disease burden. This study finds a new non-invasive indicator for diagnosing lead poisoning. A dual-channel paper-based analytical device was developed to achieve a facial measurement of the new indicator. This new lead poisoning diagnostic method addresses the limitations of traditional diagnostic methods. In summary, the new strategy proposed in this work aims to reduce the harm caused by environmental pollutants to people.