Semaglutide: research overview

Cobalamin deficits have been reported to increase over time in GLP-1 RA users in a 2026 narrative review of micronutrient deficiencies. The mechanism proposed is reduced dietary intake under sustained satiety plus delayed gastric emptying interfering with B12 release from food protein. The signal mirrors the long-documented metformin-B12 association; the two drugs are frequently co-prescribed in type 2 diabetes, and co-administration of metformin with GLP-1 RAs has been independently associated with lower serum B12 in cross-sectional analyses. Studied alongside the drug primarily through observational pharmacovigilance rather than dedicated supplementation RCTs.

Semaglutide treatment is associated with reductions in absolute lean body mass — exploratory analysis of STEP 1 reported a -9.7% change in absolute lean mass over 68 weeks, with the lean-to-fat ratio nonetheless improving because fat mass loss was larger. The SEMALEAN prospective cohort showed an initial 3 kg lean mass loss at 7 months that stabilized through 12 months, with handgrip strength rising and sarcopenic-obesity prevalence falling from 49% to 33%. Reviews of GLP-1 RA sarcopenia consistently describe high protein intake and resistance training as the principal mitigation strategies studied alongside the drug class.

Vitamin D deficiency is the most commonly observed micronutrient abnormality in GLP-1 RA users in the 2026 Urbina narrative review, rising from 7.5% at 6 months to 13.6% at 12 months. Calcium intake was below estimated requirements in more than 60% of users in the same analysis. Both deficits are mechanistically relevant to bone mineral density loss, which has been independently reported in DXA-based studies of semaglutide users — declines documented at the total hip, femoral neck and lumbar spine, particularly in patients without diabetes where weight loss drove the bone signal. Studied alongside the drug through observational deficiency surveillance.