Magnesium hydroxide may cause diarrhoea, an effect that is dose-dependent and hypermagnesaemia may occur, usually in patients with renal impairment. Very rarely, signs of potential serious effects may occur such as electrolyte imbalance (confusion, irregular heartbeat, muscle cramps, and unusual tiredness or weakness) due to acute overdosage or chronic misuse. Other signs of side effects may include bloating, nausea, gas formation and increased thirst.