Magnesium, iron and vitamin C taken on an empty stomach can cause nausea and cramps

Popular supplements taken on an empty stomach in the morning can lead to poor absorption or side effects including nausea, stomach cramps and diarrhoea. Magnesium, iron and vitamin C are among the supplements that should be taken with food rather than on an empty stomach. The timing, the type of meal and interactions with other medications also affect how well supplements work.