How common are micronutrient deficiencies in people taking GLP-1 based medication?

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Many people enjoy substantial weight loss and improvement in health with highly effective GLP-1 based medications. With the significant reduction in appetite and food intake that these medications can induce, as well as changes in food preferences for some people, it’s important to consider whether you (or your patient) are/is getting adequate nutritional and nutrient intake with treatment. As we are still lacking in clinical trial data on micronutrient levels in GLP-1 based medication studies, efforts are being made to investigate this question in other ways.

A recent study conducted an observational, retrospective analysis from an American claims database of adults newly prescribed GLP-1 receptor agonists between 2017 and 2021 with no prior diagnoses of nutritional deficiencies. About 80% of these people had type 2 diabetes. The most commonly prescribed GLP1 medications were dulaglutide (Trulicity – 38%), semaglutide (Ozempic/Wegovy – 29%), and liraglutide (Victoza/Saxenda – 28%). (Tirzepatide – Mounjaro/Zepbound – was not yet available.)

They found that nutritional deficiencies were diagnosed in 12.7% of the patients within 6 months after starting GLP1, and in 22% within a year. Vitamin D deficiency was most common. Anemia due to nutritional deficiency was detected in 4% of patients within a year.

They also compared people with type 2 diabetes treated with GLP1 and metformin, vs those treated with metformin alone. At one year, people prescribed GLP1 had a higher risk of being diagnosed with thiamine (vitamin B1), other vitamin B, and vitamin D deficiency.

They also looked at patients who saw a dietitian within 6 months of starting GLP1, vs those who did not. Those who saw a dietitian had a greater likelihood of having nutritional deficiencies detected than those who did not.

So what does this all mean? Well, these data don’t actually tell us if GLP1 medications cause nutritional deficiency. Vitamin levels were not measured/not compared to before starting GLP1, so we don’t know if these detected deficiencies were new, or whether they existed before the person started GLP1. As blogged previously, obesity, before treatment with medication, is associated with a higher risk of micronutrient deficiencies such as vitamin D, vitamin B12, folate, thiamine, iron, and zinc. Inadequate intakes of calcium, magnesium, and vitamins A, E, and C have also been reported in people with elevated weight. Regarding the comparison of people on GLP1 and metformin vs metformin alone, it is entirely possible that nutritional deficiencies were caused by the appetite changes on GLP1, but it’s also possible that nutritional tests were checked more often in the people on GLP1 medication.

One thing that is likely based on these data, is that seeing a dietitian for support is likely important for detecting nutritional deficiencies. Ideally people would be able to see a dietitian or nutritionist at the start of treatment to optimize nutrition from the start, and be alert to recommend labwork when a nutritional deficiency is suspected at baseline or during treatment.

BOTTOM LINE: It is entirely possible that the marked reduction in appetite and/or changes in food preferences that some people experience with GLP-1 based medications could result in nutritional deficiencies. People with obesity are also at higher risk of micronutrient deficiencies before starting medication. It is important to assess nutrition (ideally by a dietitian or nutritionist), check for any suspected nutritional deficiencies, and prevent/treat these appropriately – before and during GLP1 treatment. Clinical trials need to broadly and systematically assess for nutritional deficiencies.

Disclaimer: I am/have been an investigator in clinical trials of liraglutide, semaglutide, dulaglutide, and tirzepatide. I receive honoraria as a continuing medical education speaker and consultant from the makers of semaglutide and liraglutide (Novo Nordisk), and tirzepatide and dulaglutide (Eli Lilly).

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