Doctors have warned of the dangers of “alternative” medicines after a four-year-old autistic boy was hospitalised after suffering adverse effects from a cocktail of supplements.

The child, who was not named in a report of the incident, had been vomiting and constipated for three weeks and also lost 3kg in weight before he was taken to accident and emergency.

He was then diagnosed with severe hypercalcaemia, a condition in which patients have very high calcium levels in their blood.

Police were even called to investigate a naturopath who had advised the family to give their son a combination of 12 different supplements, including calcium, vitamin D, camel milk and zinc.

Parents only revealed he had taken the vitamins three days after he was admitted to hospital.

Doctors reviewing the case said it should be "routine practice" to take details of alternative therapies as part of the patient's medical history.

Writing in the British Medical Journal's Case Reports, doctors from Barts Health NHS Trust, said: "His parents were devastated that something they had given to their son with good intent had made him so unwell.

"The safeguarding team became involved as well as the police to investigate the naturopath who had advised the therapies.

"Many families view these therapies as safer “natural” options.

“But as this case demonstrates, there can be significant adverse effects which may go unrecognised due to lack of monitoring, recognition and experience with these therapies."

The boy eventually made a full recovery two weeks later.

Barts Health operates five hospitals in east and central London, including Whipps Cross Hospital in Leytonstone.

Responding to the doctors' alternative therapies warning, Jane Harris, of the National Autistic Society, said: "This awful case shows we need more professionals in place to give families accurate advice and talk to them about what really helps and how to find the right support.

"It's crucial that doctors and healthcare professionals take the concerns of families seriously and are able to talk through the potential risks of alternative therapies, even when they might seem harmless."