Medicines for Hyponatraemia (low sodium)

What it is

Hyponatraemia means the level of sodium (a salt) in the blood is lower than normal. Sodium helps regulate the balance of water in and around the body's cells, so when it falls, water can move into cells, including brain cells, which is what causes the symptoms. Mild hyponatraemia often causes few or no symptoms and is found on a blood test; as it becomes more significant it can cause tiredness, headache, nausea, muscle cramps, confusion, and unsteadiness, and severe or rapidly developing hyponatraemia can cause drowsiness, seizures and be dangerous. There are many causes, including certain medicines (such as some water tablets and antidepressants), heart, liver or kidney conditions, hormonal problems (such as an underactive thyroid or adrenal insufficiency), severe vomiting or diarrhoea, and a condition where the body holds on to too much water (SIADH). Drinking excessive amounts of water can also cause it. Finding the cause is central to treatment.

How it is treated

How hyponatraemia is treated depends on how low the sodium is, how quickly it developed, whether there are symptoms, and — importantly — the underlying cause and the person's fluid state, so assessment aims to work these out. Mild, symptom-free hyponatraemia is often managed by treating the cause and, in some cases, adjusting fluid intake (for example restricting fluids where there is too much water in the body) or reviewing a responsible medicine. More significant or symptomatic hyponatraemia needs careful medical management, sometimes in hospital, with the sodium corrected at a controlled, gradual rate — because correcting it too quickly can itself be harmful. Severe hyponatraemia with serious symptoms (such as seizures) is a medical emergency requiring urgent treatment. Treating any underlying condition (heart, liver, kidney, hormonal) is key to preventing recurrence. Because the causes and management vary, care is guided by the clinical situation.