A "healthy" and "fit" woman developed a life-threatening condition after undertaking a “New Year’s detox”.

The 47-year-old from the UK fell ill after undertaking the “cleanse”, which involved drinking increased fluids and taking a variety of herbal supplements.

She was admitted to hospital after collapsing and suffering from seizures. She also became confused and ground her teeth.

Doctors later established that she developed a condition called Hyponatraemia, which occurs when someone has abnormally low sodium levels in their blood.

Writing in BMJ Case Reports, doctors from Milton Keynes Hospital NHS Foundation Trust warned of the dangers of the “detox” and consuming “excessive amounts” of fluid or alternative remedies.

“Patients should be advised of the potential detriment done to their health of undertaking a New Year ‘detox’ especially if it involves consuming excessive amounts of fluid or alternative remedies,” their case report said.

The patient had been suffering from low mood and stress and had started taking a combination of milk thistle, molkosan, l-theanine, glutamine, vitamin B compound, vervain, sage tea, green tea and valerian root.

"The complementary medicine market is very popular in the UK and the concept of the New Year 'detox' with all-natural products is appealing to those less concerned with evidence-based medicine and more with complementary medicine," the report said.

It also urged doctors to be “vigilant” to non-prescriptive remedies after it said valerian root had also been suspected in another case of life-threatening hyponatraemia.

A man with a history of anxiety had suffered from seizures after taking herbal remedies including valerian root, it said.

Neither patient had consumed enough fluid to cause sodium levels to be depleted to such an extent, with doctors commenting that a healthy person would need to consume over 10 litres per day for this to develop.

However, they warned valerian root may have altered this threshold.

"Excessive water intake as a way of 'purifying and cleansing' the body is also a popular regime with the belief that harmful waste products can thus be washed from the body," the report said.