Madison Burgess decided to get serious about weight loss when the scale hit 91 kilograms (200 pounds). She began taking Ozempic. The medication worked better than she ever thought possible: even on the low starter dose, she lost more than 2 kg (5 lbs) within the first week.

Problems began, however, when Burgess, a 25-year-old healthcare administrator from Bloomfield, Michigan, ramped up her intake, as per the manufacturer’s guidelines. “The higher doses were rough on me,” she says. The constipation, nausea, diarrhoea and acid reflux hit hard and made eating difficult. That’s when she decided to drop back down to a lower dose and determine whether she could continue seeing benefits.

Burgess is just one of a growing number of people who are “microdosing” – a practice more typically associated with psychedelics such as LSD and psilocybin – by taking lower-than-standard amounts of weight-loss drugs such as Wegovy and Mounjaro (see “How they work”, below).

For some, the hope is to avoid side effects while losing weight, while others want to tap into the anti-inflammatory effect of these medications or reap their other benefits for the heart and the brain (see “A wonder drug”?, below). Microdosing the drugs has even been touted for extending longevity by ultra-wealthy elites like tech entrepreneur Bryan Johnson, and is rumoured to be the secret weapon of Hollywood stars wanting to look svelte for photo calls.

The question is, does this off-label, low-dose experimentation work?