Maintaining kidney health and preventing acute kidney injury from developing can often be achieved by reducing pre-renal causes such as dehydration, simple diet changes and following the 'sick day rules' strategy. These factors should all be discussed with high-risk patients.

Dehydration

Dehydration occurs when the body loses more fluid than it takes in. As water makes up two-thirds of the healthy human body, when the normal water content of the body is reduced and dehydration occurs, it upsets its balance of minerals (salts and sugar), which affects the way it functions.

Dehydration is usually caused by not drinking enough fluid, or by fluid being lost and not replaced. Illnesses such as persistent vomiting and diarrhoea, or sweating from a fever, can also contribute to dehydration. Early signs of dehydration include:

• Feeling thirsty, dizzy or lightheaded
• Having a dry mouth, lips and eyes
• Having a headache
• Feeling tired
• Having dark coloured, strong smelling urine
• Passing urine less often than usual.

The long-standing recommendation is for adults to drink eight cups (or two litres) of fluid a day. However, this varies according to individual factors such as age, climate and physical activity. A good rule is for people to drink enough so that they are not thirsty for long periods and steadily increase their fluid intake when exercising and in hot weather.

It is especially important for patients taking antibiotics for a urinary tract infection to stay well hydrated. The amount of fluid that some people drink may be restricted. For example, this might be the case for patients with heart failure or people undergoing dialysis.

Other people may become dehydrated because they choose not to drink. For example, someone with a urinary tract infection may not drink because urination is painful, or people with urinary incontinence may resist drinking if they are going to be away from home or a toilet for a while. Discussing fluid intake with patients and taking into account their individual circumstances is important when offering advice for avoiding dehydration and discussing potential acute kidney injury.