This randomized controlled trial will involve 800 elderly who are at risk of undernutrition (MUST score ≥ 1). Participants will be screened for eligibility. Recruitment will be at the polyclinic and in the inpatient ward prior to their discharge from the hospital. Participants will be randomized to intervention group vs. control group at the baseline visit at the clinical trial research unit where baseline measurements and baseline survey using the study specific questionnaires will be performed. Participants will be followed up prospectively at Day 30, Day 90, Day 180 (exit visit), and Day 360 (post-intervention follow-up visit). Repeated measures will be performed at the pre-defined time points. Intention-to-treat analysis comparing intervention group vs. control group will be performed to study the effect of ONS on primary composite outcome consisting of (i) change in body weight from baseline to Day 180 or (ii) unexpected admission to the hospital over 180-day intervention period. The effect of ONS on nutritional status will be examined by comparing the biochemical and anthropometric measurements of intervention group vs. control group at Day 180. Other outcomes such as changes in functional assessment, nutritional knowledge levels, and quality of life will also be examined. There will be a follow up visit at Day 360.