The Longitudinal Aging Study in India (LASI) is designed to be a nationally representative study of the physical, financial, and social well-being of India's 45+ population. The instrument is designed to be comparable to the Health and Retirement Study (HRS), which is a model for several studies across the world. This harmonization in instruments allows for cross-national comparative studies. In addition to a harmonized set of core questions, the instrument also reflects circumstances specific to Indian culture and institutions. The LASI instrument has three components: (1) the household survey; (2) the individual survey; and (3) the biomarker collection. Direct assessment of biomarkers, which can yield objective health measures, is particularly important in India. This report describes the following: (1) Data collection protocol, including sample sizes and response rate; (2) Laboratory protocol for the DBS assays (with the description of our quality control protocol) and the results of validation study; and (3) The distributional characteristics of biomarker data, the list of biomarker variables available in public data file, and the application procedure to obtain restricted biomarker data file.