TOPLINE:
A narrative review reported that GLP-1s in adults with obesity and/or type 2 diabetes (T2D) were linked to an increased risk for nutritional deficiencies — especially vitamin D, iron, and B vitamins — highlighting the need for regular nutritional assessment.
METHODOLOGY:As clinical use of GLP-1 drugs expands, concerns have emerged about associated nutritional and micronutrient deficiencies, particularly in individuals with obesity who are already predisposed due to poor diet quality and chronic inflammation.This narrative review aimed to synthesize current evidence on the nutritional and micronutrient deficiencies associated with GLP-1 therapy in adults with obesity and/or T2D.Researchers reviewed six studies of varying designs involving 480,825 adults older than 18 years with obesity and/or T2D who were treated with the GLP-1s semaglutide, liraglutide, or tirzepatide.The authors excluded pediatric studies; studies involving patients without obesity or T2D; case reports with fewer than 10 patients; and studies lacking nutritional, micronutrient, or body composition-related outcomes.Search results were stratified into three groups by sample size: large database cohorts, mid-sized mechanistic studies, and smaller dietary studies or case reports. The large database cohorts (Butsch et al [2025] and Salvatore et al [2025]) comprised 480,128 (99%) of the 480,825 individuals.TAKEAWAY:In the Butsch et al study of 461,382 GLP-1 users, 12.7% were newly diagnosed with a nutritional deficiency at 6 months, most commonly vitamin D deficiency (7.5%). This lack of vitamin D increased to 13.6% of GLP-1 users at 12 months. Diagnoses of muscle loss, B vitamin deficiencies, dehydration, and mineral deficiencies (calcium, selenium, and zinc) also rose over time.In another study involving 18,746 adults with T2D, GLP-1 users had a 49% higher risk for vitamin D deficiency than SGLT2 inhibitor users, a 32% higher risk for vitamin D deficiency than DPP-4 inhibitor users, and a 54% higher risk for lower levels of ferritin (iron) than SGLT2 inhibitor users.A prospective pilot study of 51 adults with T2D showed markedly reduced intestinal iron absorption after 10 weeks of semaglutide therapy.A register-based cohort study involving 439 patients with T2D and hereditary hemochromatosis showed that GLP-1 users also had 26%-30% lower ferritin levels than SGLT2 inhibitor users.In a dietary analysis of 69 GLP-1 users, most failed to meet recommended intakes for vitamin D, iron, calcium, and protein; separate case reports linked GLP-1 use to severe thiamine deficiency, including cases of Wernicke encephalopathy and beriberi.IN PRACTICE:
“Micronutrient deficiencies during GLP-1 therapy are a common consequence rather than a rare adverse effect. Additionally, findings illustrate that GLP-1 RA [receptor agonist]-associated nutritional risk is clinically relevant,” the authors of the study wrote.
“One of the objectives of this review is to raise awareness of this complication and to encourage a broader differential diagnosis in patients receiving GLP-1 therapy who present with unexplained neurologic symptoms, functional decline, or constitutional changes during periods of marked caloric restriction,” they added.
SOURCE:
The study was led by Jorge Urbina, MD, Autonomous University of Guadalajara, Guadalajara, Mexico. It was published online in Clinical Obesity.
LIMITATIONS:
The primary limitation is the reliance on retrospective database cohorts, cross-sectional analyses, and small prospective studies, with no large randomized trials conducted . Two studies had disproportionate numbers of patients, and the researchers acknowledged that this fact may skew the results.
Most studies used retrospective data and dietary recall instead of direct body composition measurements. The heterogeneous nature of GLP-1 exposure and treatment response in real-world populations further complicated the analysis.
DISCLOSURES:
The authors reported receiving no external funding. One author declared being a consultant and proctor for Intuitive Surgical and a consultant for Medtronic and Endolumik.
This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
