Health warning: Slimming product More Slim has been found to contain an undeclared drug ingredient with potentially serious side effects.

People are urged not to buy or consume slimming product More Slim which contains an undeclared drug ingredient with potentially serious side effects, the Department of Health says.

It seized 13 packs of the product from a slimming centre in Sheung Shui today after tests showed the presence of sibutramine, a drug commonly used for slimming. The centre has been ordered to recall the product.

Sibutramine can cause increased blood pressure and pulse rate. It must be registered with the Pharmacy & Poisons Board and can only be sold on a doctor's prescription and under a pharmacist's supervision.

People using the product should stop taking it and see a doctor if they feel unwell. Call the slimming centre on 2359 3882 for more information on the recall.