Study: Taking GLP-1 drugs may increase risk of key nutrient deficiencies
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- Reviewed by Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Popular GLP-1 medications such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) typically cause people to eat less. But these drugs may also alter absorption of certain nutrients. A new study suggests that these effects might put users at risk of becoming deficient in some key vitamins and minerals.
In the analysis, published in the February 2026 issue of Clinical Obesity, researchers reviewed six studies involving 480,825 adults with diabetes, obesity, or both who were taking GLP-1 drugs. Nearly all (99%) of the results came from two large-scale studies, involving mostly middle-aged and older adults. Vitamin D deficiency was the most common nutritional problem, affecting 13.6% of participants after 12 months of treatment in the largest study (some 461,000 participants, 56% of them female). Anemia due to nutritional deficiency affected 4%. Other problems included iron deficiency (3.2%) and B vitamin deficiency (2.6%).
In one of the smaller studies, which looked at three-day food records for 69 GLP-1 users, 72% took in less than recommended amounts of calcium, nearly two-thirds (64%) didn't get enough iron, and only 1.4% met vitamin D recommendations.
The researchers concluded that doctors should consider nutritional deficiencies "a common consequence" of GLP-1 therapy and monitor their patients' nutritional status accordingly. Dr. Robert Shmerling, senior faculty editor at Harvard Health Publishing, adds that people taking GLP-1 medications should make sure they're getting enough nutrients (especially vitamin D, iron, and B vitamins) and consider taking a daily multivitamin.
Image: © Tatsiana Volkava/Getty Images
About the Author
Joyce Hendley, Staff Writer
About the Reviewer
Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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