A narrative review published in Clinical Obesity examined the risk of nutritional deficiencies in adults with obesity and/or type 2 diabetes (T2D) using GLP-1 receptor agonists such as semaglutide, liraglutide, and tirzepatide.
Across six studies involving 480,825 adults, the review found that micronutrient deficiencies appear relatively common during GLP-1 therapy.
Key Findings
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In a cohort 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 increased to 13.6% at 12 months.
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Compared with SGLT2 and DPP-4 inhibitors, GLP-1 users had a significantly higher risk of vitamin D deficiency and low ferritin (iron).
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A small prospective study showed reduced intestinal iron absorption after 10 weeks of semaglutide.
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B vitamin deficiencies, including severe thiamine deficiency in rare cases, were reported.
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Smaller dietary studies found many GLP-1 users failed to meet recommended intakes for vitamin D, iron, calcium, and protein. Muscle loss and mineral deficiencies were also noted.
Clinical Implications
The authors conclude that micronutrient deficiencies during GLP-1 therapy may be more common than previously recognised. They recommend routine nutritional monitoring, particularly in patients presenting with fatigue, neurologic symptoms, functional decline, or rapid weight loss.
Limitations
Most evidence comes from retrospective database studies, with no large randomized controlled trials. Results may be influenced by study design and uneven sample sizes.
Overall, the review highlights the need for proactive nutritional assessment in patients using GLP-1 therapies.
