A mum nearly died after she drank so much water it caused her sodium levels in her blood to drop dangerously low.

Nina Munro, 41, drank around four litres of water in a day in an attempt to 'flush out' what she thought was a cold — oblivious that she was 'slowly drowning' herself.

But the excessive amounts of water, combined with medications she was taking for cold and flu 'bugs', flooded her system and she had a seizure.

Ms Munro was put in intensive care for five days in June this year while doctors battled to stabilise her levels.

'Doctors later told me they didn't know how I survived it,' Ms Munro said. 'I was slowly drowning myself and I didn't even know it.' 

She added: 'My husband said I wouldn't do anything without a glass of water by my side. I think someone was looking out for me. I thought I was a super-healthy person.

'They wouldn't let me leave (hospital) until my sodium level began to increase.

'I didn't see my daughter for five days which was so hard. I didn't want her to see me in the state I was in.

'The first few days in ICU I couldn't drink anything and when I left hospital I was on a restricted 1.5ltr diet and naturally now drink less.

'They told me to drink for thirst only.'

Drinking too much water can cause the level of sodium in the blood to fall abnormally low.

Sodium is vital for regulating the amount of water in the body and controlling blood pressure, nerves and muscles.

Too little of the electrolyte, medically known as hyponatraemia, causes a build-up of water in and around the body's cells.

This causes cells to swell — including ones in the brain — and can trigger symptoms that range from mild to life-threatening, such as headaches, vomiting and seizures.

The normal blood sodium level is 135 to 145 milliequivalents per litre (mEq/L). Hyponatraemia occurs when the level falls below 135 mEq/L.

The NHS recommends people to drink six to eight glasses of water and other fluids a day — enough so their urine is a clear pale yellow colour. 

Six weeks before being admitted, Ms Munro began to pick up minor coughs and colds and generally started feeling under the weather.

She said: 'Our daughter is at kindergarten and she's always coming home with little bugs.'

She got laryngitis and lost her voice in May, and her daughter had pneumonia — which Ms Munro unknowingly also caught a mycoplasma from — a bacteria that can cause respiratory illnesses. 

'I also had a cold, earache and a sore throat which I kept going to doctors for,' she said.

'I never felt like I had time to rest with the constant demands of parenting and work.' 

Ms Munro saw five doctors in the six-week period and was given an array of different medications and told to drink more water.

She said: 'I had three lots of steroids, three lots of antibiotics, nasal sprays and Nurofen, which also lowers your sodium - it was a perfect storm to lower my sodium.'

She started to get worse in the days before she was admitted on the June 15.

'I left a gym class as I felt I wasn't moving right,' she said.

'I went to a local hospital and they said "drink lots of water" as they thought I was having withdrawals from the steroids.'

The next day she developed a 'haze' in front of her eyes and experts told her to drink more, she recalled. 

By June 15 she had been vomiting for three days, and 'drank around four litres that day and (ate) no food'.

'I just kept thinking I needed to drink all this water to flush it out,' she said.

'I've always tried to drink at least two litres a day, if not more.'

That night her husband called an ambulance which took her to hospital.

Her sodium level was 100 milliequivalents per liter — far below the recommended minimum of 135 — with anything under this considered low.

Ms Munro said she was told by doctors the cause of her low sodium level was from drinking too much water combined with medications she had been on for recent minor colds, plus a mycoplasma infection.

She says her time in ICU was a bit patchy in memory but knows she is lucky to be alive.

After a small monitoring period, she made a full recovery and is now back to full health — although she is unable to drive for six months because of her seizure.

She said: 'I know a blood test would have showed it up straight away.

'There must be other people out there in the same boat.

'The blood test would have shown the sodium level as being very low so it could have been caught earlier.

'I think it will take a while to trust that things will be okay. It was like my body had a hard reset and had to start up again.'