Hyponatraemia may be acute (levels falling over hours) or chronic (days to weeks), and associated with altered body fluid level – either low, such as in dehydration (hypovolaemia), high (hypervolaemia), such as from heart failure, or unchanged (euvolaemia).
Blood sodium levels are normally tightly controlled by a complex bodily system. Levels usually range from 135-145 mmol/L. Mild hyponatraemia is under 135 mmol/L, severe hyponatraemia under 120 mmol/L. Mild hyponatraemia is very common in both men and women.
Patients at higher risk include elderly people who are less likely to express thirst or may be taking medicines, which