What are the possible side effects of taking Alli?

Most of the side effects with Alli affect the digestive system and are less likely to occur with a low fat diet. In general, they are mild, and occur at the beginning of treatment, going away after some time.

The most common side effects with Alli (seen in more than 1 patient in 10) are oily spotting, flatus (gas) with discharge, faecal urgency (urgent need to open the bowels), fatty oily stool, oily evacuation (bowel movements of just oil, without stool), flatulence (gas) and soft stools. For the full list of all side effects reported with Alli, see the package leaflet.

Alli must not be used in people who are hypersensitive (allergic) to orlistat or any of the other ingredients. It must not be used in people who are being treated with ciclosporin (used to prevent organ rejection in transplant patients) or with medicines used to prevent blood clots such as warfarin. It must also not be used in people with chronic malabsorption syndrome (a long-term disease where nutrients from food are not easily absorbed during digestion) or cholestasis (a liver disorder), or in women who are pregnant or breast-feeding.