One in five patients taking diuretics commonly prescribed for high blood pressure or heart conditions end up with reduced sodium and potassium levels, according to a study published in the January issue of the British Journal of Clinical Pharmacology.
But as few as a third of patients on the drugs have their electrolyte levels tested - despite the fact that reduced levels can lead to a wide range of health problems.
A team from The University of Nottingham and Queen's Medical Centre reviewed the records of more than 32,000 adults from six general practices in the East Midlands.
They found that almost one in eight had received at least one prescription for thiazide diuretics between 1990 and 2002, but only 32 per cent had had their sodium and potassium levels recorded electronically. The drug most commonly prescribed was bendroflumethiazide (bendrofluazide).
Some 21 per cent - one in five - of those who had been tested had levels that fell below the normal range.
“In a small number of patients reduced sodium and potassium levels - often referred to as electrolyte levels - can be severe enough to require hospital admission, especially if they are elderly,” said lead author Dr Jennifer Clayton.
“In milder cases they can make people feel below par, cause general weakness and tiredness and sometimes interfere with the normal rhythm of the heart.
“Severe loss of sodium can make it difficult for people to maintain their blood pressure at a normal level, causing dizziness, confusion and an increased risk of falls in older people.
“And loss of potassium can make people more susceptible to the side effects of other drugs they are taking for heart conditions.”
Other findings included: