Weight-loss injections have rapidly moved from specialist clinics to social media feeds and high-street pharmacies. Known as GLP-1 medications, they were originally developed to support those with type 2 diabetes but are now widely used to support weight loss.

These medicines mimic a hormone called glucagon-like peptide-1, which helps regulate appetite and blood sugar. By slowing digestion and increasing feelings of fullness, they often lead people to eat less and lose weight.

Evidence suggests they can support weight loss, at least in the short term. But as use has grown, so have questions about possible unintended effects on nutrition and overall health.

A recent review of evidence suggests that some people taking GLP-1 medications may not be getting enough key nutrients. These include vitamins A, C, D, E and K, dietary fibre and minerals such as iron, calcium, magnesium, zinc and copper.

Nutritional deficiencies occur when the body does not receive enough of a nutrient to function properly. Estimates of how common these deficiencies are in those using GLP-1 medications vary widely. Some research suggests that more than 20% of people may be at risk within the first year of starting GLP-1 medications, while other studies indicate the impact may be much smaller, affecting less than 1% of users.

Read more: Five things I wish people knew about supplements – by a nutritionist

As concern about potential deficiencies has........

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