"Hidden" salt in some types of paracetamol has been linked to an increased risk of heart disease and death in a large new study.

Thanks to safety messages, people are more conscious than ever about the levels of salt in their food.

But they might be unaware of the levels of salt in some medicines that they take.

Salt is used in some soluble paracetamol because it can encourage the process of the breakdown of the tablet in water.

But experts warn some people can exceed their recommended daily salt limit through a full course of salt-containing paracetamol alone.

There are now calls for front of pack warnings for paracetamol containing contains high levels of salt.

Researchers set out to compare outcomes for people who take sodium-containing soluble, or an effervescent, paracetamol and those who take the pain relief drug with no salt in it.

The team used data from 790 UK GP surgeries, which collectively look after 17 million patients.

They tracked 60 to 90-year-olds between 2000 and 2017 who had either been prescribed salt-containing paracetamol or non-salt-containing paracetamol - in tablet, capsules or oral suspension forms.

The international team of researchers tracked 300,000 people - half with high blood pressure and half without - for a year.

The study, published in the European Heart Journal, found the risk of cardiovascular disease was higher among those who took paracetamol containing salt.

The risk of heart attack, stroke or heart failure after one year for patients with high blood pressure taking sodium-containing paracetamol was 5.6 per cent, while it was 4.6 per cent among those taking non-sodium-containing paracetamol.

Among those who did not have high blood pressure, the risk of cardiovascular disease after a year was 4.4 per cent among those taking salt-containing paracetamol, compared to 3.7 per cent for those taking paracetamol without salt.

Risk of death during the follow-up period was also higher among those taking paracetamol with salt in it.

"Given that the pain relief effect of non-sodium-containing paracetamol is similar to that of sodium-containing paracetamol, clinicians may prescribe non-sodium-containing paracetamol to their patients to minimise the risk of cardiovascular disease and death," study lead author, Professor Chao Zeng from Central South University in Changsha, China, said.

"People should pay attention not only to salt intake in their food but also not overlook hidden salt intake from the medication in their cabinet.

"Our results suggest re-visiting the safety profile of effervescent and soluble paracetamol."

In a linked editorial, two experts from The George Institute for Global Health, in Australia, said the results were clear.

"The direct message from this study is clear - there are likely to be millions of people worldwide taking paracetamol on a daily basis in a 'fast-acting' effervescent or soluble formulation who are increasing their risks of cardiovascular disease and premature death," they wrote.

"Fortunately, only a small proportion of paracetamol formulations contain sodium but, with 'fast-acting' and 'fizzy' medications increasing in popularity, the adverse effects of medication-related sodium intake look set to rise rather than fall."