Suicide Prevention Lifeline Improvement Act of 2021 This bill reauthorizes through FY2027 and expands the requirements for the National Suicide Prevention Lifeline Program. Specifically, the Substance Abuse and Mental Health Services Administration (SAMHSA) must undertake efforts to raise awareness about the program and improve data collection and analysis of demographic information related to the program. In addition, SAMHSA must develop a plan to ensure the provision of high-quality service. The bill also directs the Government Accountability Office to study the program.