Micronutrient and Nutritional Deficiencies Associated With GLP-1 Receptor Agonist Therapy: A Narrative Review

Glucagon-like peptide-1 receptor agonists (GLP-1RA) such as semaglutide, liraglutide and tirzepatide are effective for obesity and type 2 diabetes mellitus (T2DM) but may predispose users to micronutrient deficiencies through appetite suppression, delayed gastric emptying and altered absorption. Given the rapid rise in GLP-1RA use, clarifying their nutritional impact is clinically important. We conducted a structured search of PubMed and the Cochrane Database (January 2019-May 2025) for adult studies evaluating nutritional or micronutrient outcomes during GLP-1RA therapy. Paediatric studies, those lacking nutrient endpoints, and review articles were excluded. Methods followed SANRA and PRISMA-ScR guidance, and data were synthesised descriptively. Six studies met the inclusion criteria, encompassing 480 825 adults. Vitamin D deficiency was the most common abnormality, occurring in 7.5% at 6 months and 13.6% at 12 months. Iron depletion was frequent, with GLP-1RA users demonstrating 26%-30% lower ferritin levels than SGLT2 inhibitor comparators. More than 60% of users consumed below estimated requirements for calcium and iron, and vitamin D intake averaged 20% of recommendations. Protein and calcium insufficiency contributed to lean mass loss, while thiamine and cobalamin deficits increased over time. GLP-1RA therapy is associated with meaningful nutritional deficiencies. Targeted nutritional assessment and individualised laboratory evaluation may be appropriate for patients at increased risk of malnutrition. Findings are mainly derived from observational datasets, and causality between GLP-1RA therapy and nutritional deficiencies cannot be definitively established.