Since treatments like OzempicWegovy or Mounjaro have reduced the figures on the scale, another market has boomed in the United States: that of supplements presented as companions to GLP-1 agonists. Between protein powders, “special GLP-1” vitamins and probiotics, patients already under treatment find themselves drowning in promises.
At the same time, the National Medicines Safety Agency has identified 376 serious adverse reactions linked to aGLP-1 between August 2023 and January 2025, including 140 in people treated for obesity, and it warns of possible risks of “significant nutritional deficiencies”. For many, the real question then becomes what supplements under GLP-1 are really useful, and which ones can harm.
GLP-1, loss of appetite and deficiencies: what the figures show
GLP-1 agonists suppress the appetite: many patients eat much less. The ANSM describes adverse effects, often digestive, and also reports anemia due to iron deficiency, loss of muscle mass and neurological damage linked to a severe vitamin B1 deficiency. For the agency, “rapid and significant weight loss can lead to various deficiencies and associated diseases“.
To limit these risks, French-speaking nutritionists especially monitor vitamin D, vitamin B12, iron, calcium, magnesium, potassium and protein intake. Many ask for a blood test before treatment, then at 3 or 6 months and around 12 months, in order to identify a deficiency before offering a targeted supplement.
Supplements considered really useful under GLP-1
At the top of the list, experts cite protein intake. When appetite drops, it becomes difficult to consume enough protein to maintain muscles. Protein powders or drinks can then complete the diet and limit muscle wasting. Some add creatine to support strength and lean mass, being careful in case of fragile kidneys.
On the micronutrient side, vitamin D and calcium protect bones, while vitamin B12 and iron limit fatigue and anemia. Omega-3s, often not present in the plate, serve as cardiovascular support. Magnesium, electrolytes, probiotics and prebiotic fibers are then discussed on a case-by-case basis for transit and digestive discomfort.
Fake “Natural Ozempic” and dangerous mixtures: supplements to avoid
Often presented as a “natural Ozempic”, the berberine actually only causes a loss of 2 to 3 kg, the order of magnitude of a placebo, while semaglutide causes a loss of around 15% of body weight after one year. In Belgium, the daily dose of alkaloids (berberine is a natural alkaloid) is limited to 10 mg, while products sold in France display levels close to 40 times higher. ANSES describes the risk of interactions “as the main health risk to the general population when using berberine“.
Nutritionists also fear “GLP-1 booster” mixtures combining berberine, chromium, alpha-lipoic acid or hypoglycemic plants with antidiabetic treatment. The ANSM has identified 36 cases of misuse, including 25 serious, with severe vomiting, acute pancreatitis or comas linked to falsified products. She recalls that “aGLP-1 are drugs“and that”The use of an aGLP-1 outside the indications provided for in its Marketing Authorization, without a prescription, or obtained outside the legal circuit of the medicine, exposes itself to serious health risks.“.