There is no malabsorption step here. The peptide does not block how the gut takes up iron, B12, or any other nutrient, and it does not flush vitamins out of the body. It works one level up, on appetite: less food comes in. When the amount of food falls and the quality of it does not rise to match, the intake of some vitamins and minerals can slip below what the body needs. Iron is worth watching when appetite stays low or iron risk is already present.

The 2025 nutrition advisory on weight-loss peptides names eight priorities for staying nourished while losing weight on these medications. Micronutrient sufficiency sits alongside protein at 1.2 to 1.6 grams per kilogram per day, managing GI side effects, hydration, fiber, sustainable habits, monitoring muscle mass, and not stacking restrictive eating patterns on top of the appetite reduction.

The advisory is direct: a smaller appetite needs more intentional food choices, not fewer.

Subclinical deficiencies (the kind that do not trigger obvious symptoms early) can show up months later as fatigue, hair shedding, or low mood. The lag is why a baseline panel is more useful than waiting for a signal.