The article introduces the Newest Vital Sign (NVS), a quick and accurate screening test for limited health literacy in primary care settings. The NVS is designed to be administered in English and Spanish, with a total of 6 questions and a time requirement of approximately 3 minutes. The test was developed through a series of pilot studies involving over 1,000 patients and was validated against the Test of Functional Health Literacy in Adults (TOFHLA). The NVS demonstrated good reliability (Cronbach's α > 0.76 in English and 0.69 in Spanish) and criterion validity, with area under the ROC curve of 0.88 for English and 0.72 for Spanish versions. Patients with more than 4 correct responses are unlikely to have low literacy, while fewer than 4 correct answers indicate the possibility of limited literacy. The NVS is suitable for use in primary care settings to rapidly assess literacy and improve communication between clinicians and patients.The article introduces the Newest Vital Sign (NVS), a quick and accurate screening test for limited health literacy in primary care settings. The NVS is designed to be administered in English and Spanish, with a total of 6 questions and a time requirement of approximately 3 minutes. The test was developed through a series of pilot studies involving over 1,000 patients and was validated against the Test of Functional Health Literacy in Adults (TOFHLA). The NVS demonstrated good reliability (Cronbach's α > 0.76 in English and 0.69 in Spanish) and criterion validity, with area under the ROC curve of 0.88 for English and 0.72 for Spanish versions. Patients with more than 4 correct responses are unlikely to have low literacy, while fewer than 4 correct answers indicate the possibility of limited literacy. The NVS is suitable for use in primary care settings to rapidly assess literacy and improve communication between clinicians and patients.