Doctors advised to warn patients cranberry ineffective for bladder infections

Doctors have also been advised to ask about the severity of symptoms and whether patients have taken painkillers before prescribing antibiotics, amid rising drug resistance.

The proposed guidelines, issued by the National Institute for Health and Care Excellence (Nice), aim to improve the treatment of those suffering from urinary tract infections (UTIs).

It is the first time Nice has published recommendations about cranberry products and UTIs.

Patients with cystitis should be told there is "no evidence" for using cranberry products to treat lower UTIs, the draft guidance for healthcare professionals states.

Those suffering from recurrent UTIs should be advised that evidence over the preventative benefits of cranberry products is "inconclusive".

UTIs are caused by bacteria and while they can sometimes be fought by the body's immune system, stronger infections require antibiotics.

Nice said healthcare professionals should ask patients about the severity and regularity of their symptoms before prescribing antibiotics, and check what they have done to manage the illness.

They may also be asked for a urine sample to test for infection to identify the most effective antibiotic for treatment.

Dr Susan Hopkins, of Public Health England, said: "Our surveillance shows that more than a third of laboratory-confirmed E.coli UTIs display resistance to key antibiotics.

"We are therefore urging GP practices and hospitals to follow the new guidelines so they can prescribe antibiotics appropriately to their patients.

"This will preserve our antibiotics so that they not only save lives today but can continue to save lives tomorrow."

Professor Mark Baker, director for the centre of guidelines at Nice, said: "We recognise that the majority of UTIs will require antibiotic treatment, but we need to be smarter with our use of these medicines.

"Our new guidance will help healthcare professionals to optimise their use of antibiotics.

"This will help to protect these vital medicines and ensure that no one experiences side effects from a treatment they do not need."

A consultation on the draft guidelines will close on June 5.